2018 Honda Accord Complaint Log

The contact owns a 2018 Honda Accord. The contact stated that while driving 70 MPH, the vehicle jerked and failed to accelerate as intended while depressing the accelerator pedal, with several unknown warning lights illuminated. The contact stated that on a separate occasion, while driving 70 MPH, the vehicle failed to accelerate as intended while depressing the accelerator pedal and the vehicle stalled. The contact was able to coast to the side of the road. The vehicle was restarted after several attempts. The vehicle was taken to the dealer; however, no cause for the failure was found. The contact stated that prior to the recent failure the vehicle was repaired under NHTSA Campaign Number: 23V858000 (Fuel System, Gasoline). However, the failure persisted. The vehicle was not repaired due to the cost. The contact was informed that some of the failures were not related to the recall. The manufacturer was not made aware of the failure. The failure mileage was unknown.

all lights on dash are on at the same time

The contact owns a 2018 Honda Accord. The contact stated that while driving at an undisclosed speed, several unknown warning lights illuminated, prompting the contact to pull over to the shoulder of the roadway where the failure persisted. The vehicle was taken to the dealer, who diagnosed a failure with the head gasket, resulting in a misfire in cylinder #3. The contact was informed that the head gasket needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure, a case was opened for a goodwill assistance claim, and the contact was referred to the NHTSA Hotline for assistance. The contact was later informed that the goodwill assistance request was denied due to a lack of service records with a Honda dealer. The failure mileage was 74,000. The VIN was not available.

While attempting to pass a slower vehicle in my 2018 Honda Accord with a 1.5L engine, the suddenly lost power and stalled down to 20 mph while I was alongside the other vehicle. This unexpected power loss put my life and the lives of others at serious life threatening risk. I immediately brought the care to a Honda dealership, where the tech was able to reproduce the issue. The performed a borescope inspection and confirmed that coolant was present inside one of the cylinders, indicating a failed cylinder head gasket. This type of failure should not happen, especially on a vehicle like this. I was the repair would cost $6,500. After researching, I learned that this is a known defect affecting the 1.5L engine and that multiple class action lawsuits have been filed. I also discovered that American Honda is aware of the problem and has instructed dealership service departments to report affected vehicles. In fact, they have even offered gift cards to service advisors who report these cases, but are charging customers for the repairs. That's nonsense. Just do a simple google search and you will discover what I did. During the failure, the check engine light and several other warning lights came on but only the check engine remained on. Since then the car has multiple indicator lights on. Despite multiple attempts to follow-up, the dealership has refused to return my calls. This is a serious life threatening safety concern that deserves immediate investigation. Thank you. Sincerely, [XXX] [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Unknown

Vehicle had a sudden loss of power. Pulled over on highway had to restart. Engine warning said Emission system problem. Had diagnostic done several codes PO300,PO301,PO302,PO303,PO304,PO172. Problem seems to be similar to the service bulletin 22-002 dated Feb 18,22 for the Honda Accord 2015-2016. It seems to be a known issue with this engine. Honda should take care of this safety issue.

Head Gasket

I own a 2018 Honda Accord Sport. About 2–3 months ago, the car began having repeated engine misfires (P0301), hesitation, and stalling while driving. At the same time, multiple dashboard warnings appear, including Steering Assist Reduced, Brake System Problem, Collision Mitigation Braking System Problem, Adaptive Cruise Control System Problem, Emission System Problem, and Hill Start Assist Problem, these failures occur suddenly while the vehicle is in motion, creating a serious risk of loss of engine power, reduced braking performance, loss of steering assist, and disabled crash-avoidance systems. I have already performed extensive maintenance: new ignition coils, a full tune-up, compression test, spark test, and battery/alternator check, yet the issues remain. Diagnostic scans also showed U0416-68 (invalid data from ABS/VSA module) in addition to the misfire. This suggests not only a fuel/propulsion defect but also a possible computer/control module failure that links engine, brakes, steering, and ADAS systems. These conditions match known recalls for the Accord, including 23V858000 (fuel pump failure), 20V314000 (low-pressure fuel pump), and 20V771000 (BCM software issue), yet my VIN does not currently show as included. The fact that multiple critical safety systems fail simultaneously makes this a major safety hazard that could easily lead to an accident if the car stalls, loses braking, or loses steering assist in traffic. I opened a case with Honda Customer Service (Case #15868389), but they refused to cover the repair since my VIN is not listed, despite the failures being identical to those described in the recalls. I strongly believe my vehicle should be included, and I request that NHTSA investigate whether the recall VIN range needs to be expanded.

I took vehicle in because of all the sensors were going off. Honda ran a systems check and said fuel injectors needed to be replaced. It is all over the internet that this is a known issue and a recall was not issued. I spent $1500 on the replacement. These should not need replacing on an 18 accord with 80,000 miles. The recall on the fuel pump has not been addressed because Honda has limited parts. How do I know this did not affect the fuel injectors

The Head Gasket is leaking at 135k miles after changing oil and filter every 5k miles and flushing coolant every 50k. Just a cursory internet search will show you how obvious the design defect is in the head bolts of the 1.5 liter turbo engine and they should be recalled.

2018 Honda Accord 1.5T EX trim and I had a head gasket completely blown at around 82,600 miles. I, alongside with many many other 1.5T Accord owners, am experiencing this head gasket issue for such a low milage vehicle and it is simply inacceptable and Honda seems to be entirely ignoring this widespread, recurring problem on this engine. Reaching out and file a report in hopes of getting this to Honda's attention so they can address this asap. It has been 7 years since this problem and nothing has changed, which is not okay.

During interstate driving vehicle detected both road departure and engaged the emergency automated braking. The vehicle attempted to correct the "road departure" by steering the vehicle away from the perceived problem and engaged the brakes nearly causing a collision as it has done numerous times before. I have reported this to NHTSA and American Honda and await a repair of this dangerous issue. Honda has opened a case on this but have had 6 months and no response has been issued.

Honda needs to recall all the newer vehicles starting with 2018 to 2024. All lights on the dashboard is on and while I’m on highway, the car would apply the brake itself and when I released my foot from the pedal, the car run smoothly again. I took the car to Honda dealership last year and I was charged over 1500 dollars, still the car is having the same issue. This is frustrating. Today, the car is showing the camera like I was trying to back up, even though the car was on drive mode. Unbelievable.

Car goes in limp mode once the brake system lights come on. When the brake light system comes on, none of the functions for the automatic breaks or electrical portion of my vehicle works. The car will act as if it will not accelerate right before the codes start to appear on the car.

All lights on head dash are on , all components are not working properly or effected because of this. (Engine light brake light abs light tire light traction control light , sensors out all) while driving vechile reduces power does not operate randomly , have to pull over shut the car off and turn it back on. Has high vibrations lot of shaking, stauling. I have had it looked at with multiple shops and dealer . Everybody is playing a guessing game and can not pin point what exactly it is . Was told it was spark plugs and coils, alternator , fuel injectors. ALL have been repaired, and still have all lights on dash and still facing every problem listed after repairs. Been inspected by manufacturer. Say not been resolved was told if it wasn’t what was already fixed they don’t know and that this is very common right now . It first started about a month ago.

Car keeps slamming on brakes on interstate Car keeps misfiring cylinders 1.5 Head gasket problems should have a recall with these Honda as much as they give problems..

While accelerating uphill approximately 65 mph the car suddenly started to shutter and slow down to 35 mph. I forced me to move rapidly over to the right lane on a busy highway almost getting hit by a semi truck. Luckily I was able move to the shoulder and park the vehicle. I shut the vehicle off and tried to start it back up which it did but struggled to turn over. Using my OBDII scanner I found that multiple codes had appeared which included P0087 Fuel Rail/System Pressure to low and P0299 Turbocharger Underboost. Vehicle was towed to my residence where it currently sits until I am able to repair it. Prior to this happening there were No warning lamps or messages or symptoms. The failures first appeared while driving up hill. It was not inspected by manufacturer, police, or insurance. The problem was not taken to dealer or independent service center to confirm since the car is out of warranty and cost to diagnose is ridiculously high. I myself diagnosed the failures and found that the mechanical fuel pump Part# 16790-5PC-H02 seized up and was not providing enough fuel to engine. And diagnosed that the waste gate actuator arm was to loose due to worn out bushings. (Poor engineering in my opinion since there is no way to replace just the bushings on the actuator causing customers to replace the entire turbo.) After replacing the mechanical fuel pump the vehicle was able to start up without issue and drives perfectly fine. I currently still have the fuel pump and the turbo is still in the vehicle if needed for inspection.

On 2025-06-12 at about 3:50 PM EST I triggered a remote start command from my phone via the HondaLink app to cool down the car before leaving work. When I went out to the car it had not started. I assumed the command had simply failed, so I returned home and parked in our attached 2-car garage at around 5:10 PM. At about 6:30 PM I opened the door between the house and the garage and heard an engine running. The car was found to have spontaneously started itself. I do not know precisely how long it had been running. It took me a couple seconds to recognize the situation and the danger, and once I realized what had happened I immediately closed the door to prevent carbon monoxide from entering our house. I tried accessing HondaLink to shut down the vehicle remotely but the app gave a message "Services Currently Unavailable". In order to safely shut it down, I opened the garage doors, waited a couple minutes for the garage to ventilate, then quickly moved in and shut down the engine while avoiding breathing in. We noticed a smell of fumes in our house near the connecting door. Both keys were in static locations (not in pockets, etc. where the buttons could have been accidentally pressed). They had been that way since I got home. I believe that HondaLink's servers sent the remote command to my vehicle *significantly later* than the command was requested. This is a major problem and safety checks should prevent a delayed command from having an effect on the vehicle, especially when dealing with engine start commands. The carbon monoxide buildup fortunately seemed to be minimal, although I am again unclear exactly how long the engine had been running. The vehicle will normally shut itself off 10 minutes after a remote start. However, the most dangerous situation would have been if the car shut itself off and then someone entered the garage shortly afterward without realizing that the vehicle had been running.

This is about the 5th time this has happened to the car. All warning lights appeared spontaneously while driving. The lights would turn off if the car was turned off for a long period of time or is we disconnected battery for a long period of time. We have tried to research the problem and no one seems to know what the cause or permanent fix is.

All lights in dash is on took it to honda they playing a guessing game injectors head gasket sensors they really don’t know many people are complaining with the same problems

Car falls into limp mode in traffic when a misfire is detected. I have had a mechanic investigate the misfire and has determined coolant in the cylinders, indicating a blown head gasket. This is a widely reported problem with this engine and the large number of complaints indicate this is a safety issue caused by Honda.

The vehicle was totally inoperable and suddenly came to stop was lucky that was driving in a local road where there was no vehicle, suddenly all different warning signs were coming on the dashboard and couldnt drive at all and vehicle was totally stalled. it was very dangerous situation luckliy i was just came off a very busy road otherwise coudl have been major incident. Currently the vehicle is at dealership nto sure what they will say but just wanted to report this as it is very dangerous situation

My 2018 Honda Accord has become unsafe to drive. The car will not go over 15 mph, all the warning lights on the dashboard are on, and the engine and transmission feel shaky. The entire car shakes when I try to drive it, and it seems like multiple systems are failing at once. This happened suddenly and has made the car undriveable. My safety was put at risk because the loss of power happened while I was on the road. The problem has been looked at by my independent mechanic, but it has not been resolved. The vehicle is available for inspection.

The vehicle experienced a rough idle and white smoke blowing out the exhaust on a cold startup. It did have coolant loss over a period of time with no visible leaks. I waited until I got a check engine code that revealed a misfire in cylinder 4. Upon further diagnostic testing it was revealed that the head gasket was blown between cylinders 3 and 4. I paid for the repair out of pocket only to see that this is a very common issue with the 1.5 turbo engine.

The contact owns a 2018 Honda Accord. The contact stated while driving at an undisclosed speed, the vehicle stalled and then went into LIMP Mode. The vehicle was able to be restarted. The contact received notification of NHTSA Campaign Number: 23V858000 (Fuel System, Gasoline). The dealer was contacted and confirmed that parts were not yet available. The manufacturer was made aware of the failure. The failure mileage was approximately 150,000. Parts distribution disconnect.

The head gasket is leaking. Yes, the dealer reproduced and diagnosed the problem. There were no lights on the dash. It is available for inspection if needed.

The contact owns a 2018 Honda Accord. The contact stated that while driving 30-35 MPH, the vehicle overheated and stalled. Several unknown warning lights were illuminated. The contact pulled over and turned on the hazard lights. The vehicle was taken to the local dealer on three occasions and was diagnosed with a blown head gasket and engine failure. The vehicle was repaired, but the failure recurred. The vehicle was not repaired. The manufacturer was contacted and provided financial assistance. The failure mileage was approximately 70,000.

The contact owns a 2018 Honda Accord. The contact stated while driving at approximately 60 MPH, the vehicle lost automotive power, and unintendedly shifted to LIMP Mode. The contact stated that several unknown warning lights were intermittently illuminated. The vehicle was taken to a dealer where it was diagnosed that there was an internal coolant leak, and that the head gasket needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 164,897.

Bad fuel injectors reported by diagnostic testing done by Honda dealership after recall was completed on fuel pump. All warning lights on dashboard lite up and multiple warnings from car. This is a known issue with these specific Honda engines. Very costly repairs that if not completed can cause other engine issues.

Car has been giving me issues with the check light engine. They changed spark plugs and the head gasket and still giving me issues.

Blown Head Gasket after taking my car in to Honda cars of Rock Hill SC, I had no issues, only took it to have the Fuel injector recall done, they did a diagnostic nothing came up, they did the fuel injector recall repair, and they asked if they could do the oil change i told them yes, a week later, my car lost power on interstate 77N in rock hill south carolina. I was going about 70 mph and it dropped from 70 to 20 mph in a matter of seconds, i had little time to get out the lane, i could have been killed or killed someone else i was terrified. Every known light on my 2018 honda accord came on, I have a video of the lights on my dashboard. I had it towed back to honda cars of rock hill on 5/30/2025 and was told I had a blown head gasket...I asked them how, they just put a fuel injector and nothing else was wrong with my car. they told me cost is $5500.00, i told them there as nothing wrong with my car prior to them doing the recall, Matt told me there was nothing i did, so i asked him what did they do to my car, I need them to replace my motor who knows what other damage happened my car had no issues.

Have had several misfires, nothing would fix it. Dealership looked at it and said the injectors needed to be replaced. Replaced injectors and still had misfire issues. Car is consuming coolant, and there is exhaust is the cooling system. Meaning blown head gasket.

Head gasket issues and turbocharger issues

Vehicle: 2018 Honda Accord Sport 1.5T, VIN [XXX] , 108,584 m, registered Indiana. Vehicle suffered from well-known 1.5L turbo oil dilution defect (TSB 19-091) since 5/24/21, 35k m, towed Honda dealership check engine light on, loss acceleration. Dealership diagnosed misfires cylinders 2 &3 caused by faulty fuel injectors from gasoline contaminating engine oil, 4 injectors,related parts $1,495.53. Defect persisted, ongoing issues: VTEC solenoid failure, spool valve replacement, turbo full assembly replacement, multiple spark plug replacements over four+ years, due to same oil dilution causing fouling/misfires. $3,855+ spent related repairs, due to defect. 6/14/25 & 6/21 car decelerated, 9 warning lights illuminated. Examined, diagnostics clear. 10/29/25 engine light, loss of acceleration, almost resulted in highway crash. Towed Victory Honda Highland, IN 11/10, sat 40+ days. No communication. Eventually diagnosed blown head gasket, leaking injectors. No loaner provided despite request. Corporate requested teardown 11/25 wasn’t done. Manager demanded deposit before teardown. American Honda denied goodwill, refused escalation 3xs, assigned same unresponsive manager, but out till New Year. Broke 48-hour callback promise 12/17. Upon request, Honda towed Team Honda Merrillville, IN no repairs done at Victory. Since transported Team Honda nothing repaired, waiting teardown confirmation, leaving my family without transportation 2+ months. Defect documented TSB 19-091, ongoing class-action suit 1:22-cv-02662, N.D. Illinois 1,200+ NHTSA complaints identical failures. ‘18 Honda Accord Sp 1,200 + documented similar complaints, yet Victory Honda, Team Honda, & American Honda not addressed issue. Lack of communication, refusal to address known safety issue. Should investigation/mandatory recall/coverage. Safety Risk: Sudden loss of power on highway = crash hazard. Spent $3,855+; car undrivable, family without vehicle to/from work. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

While driving my 2018 Honda Accord Sport 2.0T, I experienced sudden coolant loss and engine overheating. Upon inspection by a mechanic, it was confirmed that the cylinder head is cracked, which is a known issue on the 2.0T engine. This creates a serious safety hazard because it can cause engine failure while driving, loss of power, or even fire risk if coolant mixes with oil. Honda has not issued a recall, but multiple owners have reported this same problem, and I believe it is a manufacturer defect. This should be investigated as it directly affects vehicle safety and reliability. symptoms: Overheating, coolant disappearing, white smoke, loss of power, warning lights, etc.

UNKNOWN I received the notice that there was an active recall on my 2018 Honda about the 1.5 Fuel Pump. I have scheduled several appointments to fix this, only for Honda to cancel all appointments related to the recall, stating they didn't have the part. I was headed to work, and every light on the dashboard that could come up, came up. There were several warning lights from brakes, transmission, collision, engine, etc. I took the car to the dealership, and they discovered that the fuel injector was the culprit. I am outraged because they're denying there's a connection, and I believe otherwise.

Hello, the fuel pump which is recalled on my vehicle failed and was replaced with an aftermarket pump so I could take it to the dealership. Once I took it the dealership refused to go ahead with the recall and basically told me it’s not their problem. They are required to get it done for customers but they refused to fix mine.

My 2018 Honda Accord Sport has been experiencing issues with its automatic emergency braking system, specifically the Collision Mitigation Braking System (CMBS). The system has been activaing unexpectedly, causing the car to brake without an apparent reason. I’ve been trying to keep a list of locations that it has happened and it usually occurs under overpasses when the light changes from light to dark. I’ve reached out directly to Honda and the dealership and neither took my inquiry seriously.

My 2018 accord sport started randomly started popping up a “supplemental restraint system problem” on my dashboard. It’s turns on and goes away randomly. I went to my local Honda dealer and I asked them about it and they had to preform a diagnostic for $250. Our Honda dealer wants to charge $4000 to repair it. I wrote to American Honda and submitted a support ticket, they asked for a new Diagnostic and charged us another $250. They called me back yesterday saying that they wont pay for the repairs unless there is a recall. How many people need to have the same issue to initiate a recall? There are a lot of complaints online for this same thing. It is airbag safety related.

Various 2018-2022 Honda Accord owners had fuel injector failures caused by the faulty factory fuel pump molding. The fuel pump has been recalled; however, not before the fuel injectors fail. My Accord recently got an array of warning lights pop up on the dash while driving on the highway. I read the code and it was a cylinder 3 misfire. A diagnosis has led to the discovery that the fuel injectors are failing, most likely because of the bad fuel pump molding affecting the pressure of the fuel lines. Not only could this have led to my car stalling on the highway, it led to a complete disabling of my safety features while driving. Honda should be held responsible for the fuel injectors failing caused directly by their fuel pump molding deviation.

The contact owns a 2018 Honda Accord. The contact stated while at an undisclosed speed, the Supplemental Restraint System (SRS) message was displayed. The contact stated that the message was displayed at start up and remained displayed until the vehicle was turned off. The vehicle was not diagnosed or repaired. Upon further investigation, the contact became aware that the SRS message warned about a failure with the safety features designed to protect occupants during an accident. The manufacturer was not notified of the failure. The failure mileage was approximately 94,000.

Engine keep going into limp every now and then and it’s pretty dangerous especially while driving on the highway. All the lights would come on the dashboard. On May 2 it almost cause an accident because it happened while I was driving on the freeway and I’ve changed spark plugs, injector my battery and it’s happening

I purchased this 2018 Honda Accord that has had no major problems until the last 6 months. I purchased the car from Gerald Jones Honda and have had all repairs and maintenance done there with the exception of tire related concerns and occasional oul changes. All the issues I've experienced have been engine related and in the same area of the engine. Consistent leaks, repeated warning lights, and loss of speed. I have replaced fuel injectors, a head gasket, and a turbo in the last 6 months. Despite those repairs, I'm still experiencing leaks and flashing warning lights. Honda currently has my car due to warnings again. They have indicated it is a performance issue but can't locate the problem. Even suggested I continue to drive the car as they have been unable to duplicate what caused it. I told them to keep it because that makes no sense for me to drive it as it seems unsafe to do so and I could potentially make matters worse. I've spoken to several 2018 Accord owners who have experienced the same issues. This is very concerning to me and crippling my finances. Honda stands out for their reliability, but regrettably the 2018 1.5L turbo doesn't stand up to Honda's reputation.

If car is idling for over 1 minute, all lights on dash come on. When all lights on, car wont wont go over mph, car will randomly sputter in highway when going over 1rpm and will stall randomly. Reported on reddit by multiple people and when I went in to get it diagnosed it was the fuel injector issue

This car had a manufacturer recall for the "fuel pump". I was advised by Honda to go get the car checked by the dealer to evaluate if the issues I was getting were related to the recall. I paid close to $400 to get the car diagnosed and about 3/4 months after that I was told that the part is available for the recall service. I got the repair scheduled at the dealership and got the part replaced. Ever since I got this fuel pump replaced, now the car is struggling to pickup. It looks like a miss fire but it doesn't show any errors on display. In this condition, this car is not safe to drive around as it is skipping the engine thrusts. I have looked at Honda website and other online resources and people are talking about these issues but HONDA hasn't said or done anything about it. It all started after I got the fuel filter replaced.

3 weeks after having this vehicle, the car started running hot and experiencing all types of jerking problems. I started to do my research on why suddenly the car was running hot, jerking, and other things. I noticed a thread line expressing the EXACT same issues that I was experiencing which were from bad head gaskets. I took my vehicle to the dealership to have this issue checked and verify. I also had an independent mechanic shop evaluate the vehicle as well. Both results were the same. This is a design flaw on the manufacture behalf and I reached out to the Honda Corporate only to be denied assistance with fixing the known issue because it was “out of the date” range for their goodwill claim. This vehicle will run hot and you will have to pull over on the side of the road to allow engine to cool in order for it to operate.

• Head gasket • None of the safety features work when there is a head gasket issue. Power steering is reduced as well as break performance • Confirmed by Honda dealership with a Boroscope • Honda • No warning, Honda at first thought it would be fixed by fixing the factory recalls. Light went away prior to taking it in and then looked in to it 2 weeks later and diagnosed head gasket failure

The contact owns a 2018 Honda Accord. The contact stated that while attempting to start the vehicle during cold weather, the vehicle hesitated while starting. The contact stated that while driving at an undisclosed speed, the vehicle independently went into LIMP Mode. The check engine warning light illuminated. The vehicle was taken to a local dealer, where it was diagnosed with a blown head gasket and a GDI injector failure. The vehicle was not repaired. The manufacturer was made aware of the failure. The failure mileage was approximately 116,000.

The 1000 miles or so, when trying to increase speed, would feel the gears slip between revolutions. I would let up on the gas pedal then slowly resume pressure, which sometimes worked or sometimes didnt. On April 19th while going up a hill on a side road, the car stalled and transmission warning light came on. I pulled over and shut the car off and restarted was able to slowly continue up hill at 15 miles per hour with the slipping becoming worse ( this is when I first called Honda to bring it in on Monday April 21.) I was able to arrive to work. After leaving work I pulled out of the parking lot and the car just stalled with all lights and warnings going off from engine to airbag warnings to tire pressure lights going off and dinging. This is when i called a tow truck to tow to the Curtiss Ryan Dealership. After talking to them at dealer they told me that other accords have had this problem.

Car has 60,675 miles with a blown head gasket. Prior to blown head gasket vehicle was brought to Honda in April 2025 for overheating, rough start and leaking coolant and was told fuel pump had a recall so it was changed, Honda did the recall repairs, performed oil change and checked everything else and released the car in working order but a week later after adding 175 miles more to the car it started overheating and had a rough start, the car was immediately brought back to Honda and they said it was a blown head gasket, the car was driven home that same day and left in the driveway undriven until September 3rd 2025 when it was towed to a different Honda dealership where it was confirmed to be blown head gasket and the cost is estimated at $6800 to repair. The car has had all recall issues addressed as well as all service and oil changes done to the vehicle, the car is driven for leisure and never in an unsafe or harmful way that could damage a head gasket.