Engine went hot once + check engine sign days later (coincidence?)

[Rockeim]

Good day from Norway, NSX owners!

I finally bought my dream car, a '91 NSX manual (not in snap ring range). The car is well maintained and doesn't carrie the stamps of a 30 year old car - interior isn't worn, exterior's flawless because it's newly been repainted (not crashed) by previous owner who's a car painter and an engine department that looks mint).

As you guys know, it's a dream to drive. Gone under 100 000 km (60 000 miles). The way its handling and the killer engine going all the way to 8 000 RPM. Unbelievable They say you shouldn't meet your idols. The NSX didn't disappoint.

I've driven it for about 1 500 km (almost 1 000 miles) without problems, until a couple days ago.

- Out of nowhere, the engine went really hot one day as it was standing still on idle (we were outside taking pictures as we suddenly saw smoke from the engine) and some coolant leaked from the car. Stopped it right away. Was tricky to locate where the leakage originated from, couldn't find any broken hoses. I checked under the car the same night and found this rubber cap with a small hole in it (can't seem to figure out what it is), and this component seemed wet when I searched the engine earlier that day. It's NOT been leaking anything afterwards (I've also tested and revved the engine). Water pump's been changed with the timing belt on 92 000 km.

I drove the engine relatively hard (not overly) beforehand. Could it be that it pumps some extra coolant through a channel when needed, and the hole in the rubber cap caused the leakage and that's why it didn't get sufficient cooling, or is it a case of top gasket failing when engine runs hard..? Read a little bit about that..

- Couple days and km's later (might just be a coincidence), after driving like 30 km with TCS off (which I usually don't, just testing), the check engine light came on. Pulled over and stopped the car immediately, everything seemed fine. Got off again and it comes on after 2 minutes when accelerating (didn't hit the TCS button this time, ergo it's on). Stopped again and read that it could be anything really, but could also be a minor thing like the gas cap lid. Seemed to sit tight, but I opened and closed it again. Drove home for 20 km, no sign popping up. Any idea? Thinking about bringing it to a work shop where they can check the codes.

Would really appreciate if you would share your knowledge on this one. I've been planning to do a 3-4 day car trip in just a couple of days before winter's coming and I have to storage it, hoping this is some minor issues that won't affect regular daily driving the next days.

Tried posting once with a picture attached but didn't seem to post, so trying this time without (attaching later). Feel free to move this thread to another category if it's in the wrong one.

Best regards, Rockeim.

 

[Big McLargeHuge]

Welcome.

For your first point, a pic would be needed of the cap you're talking about. The engine should not be overheating with a minor leak as you say unless you're already low on coolant, so make sure before you start the car that the coolant bottle is filled properly regardless of what issue you're having. There are 20+ coolant hoses and connections on the car and any one of them could be causing the leak, so there would need to be more investigation there, perhaps by your work shop. Overheating the engine at any point might cause a head gasket failure so it would be prudent to give the entire cooling system a once-over (radiator, all hoses, clamps, fluid level, trapped air, water pump leaks, etc.). Unlikely to be a water pump issue if the recent work was done properly.

The second point, you don't need a shop to check your engine codes, there is no OBD port or whatever to plug into, it's very easy to do yourself. Use a paper clip or similar, find the small blue 2-pin connector in the passenger footwell under the glove box, and short the two pins of the connector together. Turn the key in the ignition until the lights come on (not starting the engine), and record how many times the MIL blinks (long blinks = multiples of 10, short blinks = 1). Three CELs will be stored until you remove & re-insert the 7.5A clock fuse inside the front hood fuse box which will reset all the codes.

Once you have the CEL codes, then you can diagnose the issue further. There's not really any info to go on yet so I'll refrain from making guesses, so next step is to read the stored codes. This wiki page is useful https://www.nsxprime.com/wiki/Trouble_Codes.

 

[Rockeim]

Thank you so much for your complementary answer, Big, appreciate it!

Something to consider for sure about the coolant once-over. Need to replace the steering rack before next season so a full service will be done then. I drove it 30 km again today, no overheating or leakage (or check engine light-sign, didn't touch the TCS neither tho). Wonder what caused the leak.

Excellent! Didn't know it was that easy to check engine codes yourself. Gonna check it out tomorrow, then I'll know for sure if it's safe to do a trip or not. Thanks again!

 

[Old Guy]

Do you know that the engine actually over heated (engine coolant gauge went above normal) or are you assuming that you had an overheating condition because you had the release of steam and some coolant? The release of steam and coolant could be something as simple as the pressure cap on the expansion tank opening prematurely releasing some coolant or insufficient expansion room in the expansion tank after fast driving followed by stopping the car which reduces air flow through the radiator. If the coolant has not been changed regularly and the system flushed you may have a slightly plugged radiator which reduced its cooling capacity and contributed to the coolant overflow. The safe thing would be to do a pressure test of the cooling system to confirm that the system holds pressure. If the system passes the pressure test then as a precaution I would replace the pressure cap with a new cap and make sure that the coolant level is at the correct level in the expansion tank - allowing room for expansion as the coolant heats up.

When the water pump was changed were the coolant hoses replaced and the cooling system completely flushed? If you don't know it would be appropriate to plan for replacement of all the coolant hoses which will involve complete replacement of the coolant. If the coolant has not been regularly replaced then it would be good to clean the system with a cleaner prior to refilling with new coolant. Removal of the radiator to have it cleaned might be good if you suspect that the engine is running hot.

If the cooling system fails the pressure test, then a completely new game plan is required.

The CEL (Honda calls it a MIL) lighting up is likely unrelated to your engine burping coolant. Do as advised by McLargeHuge and retrieve the error codes to find out what is causing the CEL.

 

[goldNSX]

Good question of [MENTION=26435]Old Guy[/MENTION] if it was only steam or gauge in the red.

Could it be that it pumps some extra coolant through a channel when needed, and the hole in the rubber cap caused the leakage and that's why it didn't get sufficient cooling, or is it a case of top gasket failing when engine runs hard..? Read a little bit about that..

Do you mean the rubber cap in the front compartment (under the hood)? If it's the part I think you mean that's the bleeding point of the cabin heater unit of the coolant system. There have been several reports of failure of that cap. Honda changed it for that reason I guess in 1997 (?).

In general, the answer to your question is NO. The only built-in 'release point' is the coolant cap in the engine bay.

Not sure about the service history of your car but it's worse in Europe than in the US in general. I'd inspect the cooling system thoroughly before driving it any further. With some luck the engine didn't overheat.

 

[Rockeim]

Welcome.

For your first point, a pic would be needed of the cap you're talking about. The engine should not be overheating with a minor leak as you say unless you're already low on coolant, so make sure before you start the car that the coolant bottle is filled properly regardless of what issue you're having. There are 20+ coolant hoses and connections on the car and any one of them could be causing the leak, so there would need to be more investigation there, perhaps by your work shop. Overheating the engine at any point might cause a head gasket failure so it would be prudent to give the entire cooling system a once-over (radiator, all hoses, clamps, fluid level, trapped air, water pump leaks, etc.). Unlikely to be a water pump issue if the recent work was done properly.

The second point, you don't need a shop to check your engine codes, there is no OBD port or whatever to plug into, it's very easy to do yourself. Use a paper clip or similar, find the small blue 2-pin connector in the passenger footwell under the glove box, and short the two pins of the connector together. Turn the key in the ignition until the lights come on (not starting the engine), and record how many times the MIL blinks (long blinks = multiples of 10, short blinks = 1). Three CELs will be stored until you remove & re-insert the 7.5A clock fuse inside the front hood fuse box which will reset all the codes.

Once you have the CEL codes, then you can diagnose the issue further. There's not really any info to go on yet so I'll refrain from making guesses, so next step is to read the stored codes. This wiki page is useful https://www.nsxprime.com/wiki/Trouble_Codes.

Wow, thank you so much all for the quick and complementary answers, really appreciate it! Good people.

Something to consider for sure about the coolant once-over. The car's been taken well care of, but better to be safe than sorry. I do not know if it's been completely flushed but I will check up on that as it was a premium autoshop that once dealt with the car. I will need to replace the steering rack before next season so a full service will be done then. Drove it 25 km again yesterday, no overheating nor leakage (or CEL-sign, didn't touch the TCS neither tho). Still wondering what caused the leak but good points by all of you, might just be pressure cap on the expansion tank (as described; driven fast followed by stopping the car idling).

Do you know that the engine actually over heated (engine coolant gauge went above normal) or are you assuming that you had an overheating condition because you had the release of steam and some coolant? The release of steam and coolant could be something as simple as the pressure cap on the expansion tank opening prematurely releasing some coolant or insufficient expansion room in the expansion tank after fast driving followed by stopping the car which reduces air flow through the radiator. If the coolant has not been changed regularly and the system flushed you may have a slightly plugged radiator which reduced its cooling capacity and contributed to the coolant overflow. The safe thing would be to do a pressure test of the cooling system to confirm that the system holds pressure. If the system passes the pressure test then as a precaution I would replace the pressure cap with a new cap and make sure that the coolant level is at the correct level in the expansion tank - allowing room for expansion as the coolant heats up.

When the water pump was changed were the coolant hoses replaced and the cooling system completely flushed? If you don't know it would be appropriate to plan for replacement of all the coolant hoses which will involve complete replacement of the coolant. If the coolant has not been regularly replaced then it would be good to clean the system with a cleaner prior to refilling with new coolant. Removal of the radiator to have it cleaned might be good if you suspect that the engine is running hot.

If the cooling system fails the pressure test, then a completely new game plan is required.

The CEL (Honda calls it a MIL) lighting up is likely unrelated to your engine burping coolant. Do as advised by McLargeHuge and retrieve the error codes to find out what is causing the CEL.

True, I do not know for sure that it ACTUALLY overheated (I really hope not), but the gauge for sure went above normal. We first saw some smoke coming from the engine bay, I jumped back in and stopped it right away. As I was kinda stressed, I do not remember if the gauge actually touched the red line or not, but it was for sure right up there. Hopefully I got it on time. Seconds later some coolant leaked out.

Excellent, didn't know it was that easy to check engine codes yourself. Gonna check it out today, then I'll know for sure if it's safe to do a small trip or not. Thanks again!

 

[Rockeim]

I've replied long answers a couple times already but it never gets approved, does it take this long all the time..??

 

[Old Guy]

That sounds more like a time out issue. Since you can obviously make short posts, try doing multiple short posts with individual questions or answers.

 

[goldNSX]

Keep it as short as possible.
Before definitly sending your answer hit CTRL+C (copy).

 

[Rockeim]

Welcome.


For your first point, a pic would be needed of the cap you're talking about. The engine should not be overheating with a minor leak as you say unless you're already low on coolant, so make sure before you start the car that the coolant bottle is filled properly regardless of what issue you're having. There are 20+ coolant hoses and connections on the car and any one of them could be causing the leak, so there would need to be more investigation there, perhaps by your work shop. Overheating the engine at any point might cause a head gasket failure so it would be prudent to give the entire cooling system a once-over (radiator, all hoses, clamps, fluid level, trapped air, water pump leaks, etc.). Unlikely to be a water pump issue if the recent work was done properly.


The second point, you don't need a shop to check your engine codes, there is no OBD port or whatever to plug into, it's very easy to do yourself. Use a paper clip or similar, find the small blue 2-pin connector in the passenger footwell under the glove box, and short the two pins of the connector together. Turn the key in the ignition until the lights come on (not starting the engine), and record how many times the MIL blinks (long blinks = multiples of 10, short blinks = 1). Three CELs will be stored until you remove & re-insert the 7.5A clock fuse inside the front hood fuse box which will reset all the codes.


Once you have the CEL codes, then you can diagnose the issue further. There's not really any info to go on yet so I'll refrain from making guesses, so next step is to read the stored codes. This wiki page is useful https://www.nsxprime.com/wiki/Trouble_Codes.

Wow, thank you so much all for the quick and complementary answers, really appreciate it! Good people.


Something to consider for sure about the coolant once-over. The car's been taken well care of, but better to be safe than sorry. I do not know if it's been completely flushed but I will check up on that as it was a premium autoshop that once dealt with the car. I will need to replace the steering rack before next season so a full service will be done then. Drove it 25 km again yesterday, no overheating nor leakage (or CEL-sign, didn't touch the TCS neither tho). Still wondering what caused the leak but good points by all of you, might just be pressure cap on the expansion tank (as described; driven fast followed by stopping the car idling).

 

[Rockeim]

Welcome.


For your first point, a pic would be needed of the cap you're talking about. The engine should not be overheating with a minor leak as you say unless you're already low on coolant, so make sure before you start the car that the coolant bottle is filled properly regardless of what issue you're having. There are 20+ coolant hoses and connections on the car and any one of them could be causing the leak, so there would need to be more investigation there, perhaps by your work shop. Overheating the engine at any point might cause a head gasket failure so it would be prudent to give the entire cooling system a once-over (radiator, all hoses, clamps, fluid level, trapped air, water pump leaks, etc.). Unlikely to be a water pump issue if the recent work was done properly.

Wow, thank you so much all for the quick and complementary answers, really appreciate it! Good people.


Something to consider for sure about the coolant once-over. The car's been taken well care of, but better to be safe than sorry. I do not know if it's been completely flushed but I will check up on that as it was a premium autoshop that once dealt with the car. I will need to replace the steering rack before next season so a full service will be done then. Drove it 25 km again yesterday, no overheating nor leakage (or CEL-sign, didn't touch the TCS neither tho). Still wondering what caused the leak but good points by all of you, might just be pressure cap on the expansion tank (as described; driven fast followed by stopping the car idling).

Do you know that the engine actually over heated (engine coolant gauge went above normal) or are you assuming that you had an overheating condition because you had the release of steam and some coolant? The release of steam and coolant could be something as simple as the pressure cap on the expansion tank opening prematurely releasing some coolant or insufficient expansion room in the expansion tank after fast driving followed by stopping the car which reduces air flow through the radiator. If the coolant has not been changed regularly and the system flushed you may have a slightly plugged radiator which reduced its cooling capacity and contributed to the coolant overflow. The safe thing would be to do a pressure test of the cooling system to confirm that the system holds pressure. If the system passes the pressure test then as a precaution I would replace the pressure cap with a new cap and make sure that the coolant level is at the correct level in the expansion tank - allowing room for expansion as the coolant heats up.


When the water pump was changed were the coolant hoses replaced and the cooling system completely flushed? If you don't know it would be appropriate to plan for replacement of all the coolant hoses which will involve complete replacement of the coolant. If the coolant has not been regularly replaced then it would be good to clean the system with a cleaner prior to refilling with new coolant. Removal of the radiator to have it cleaned might be good if you suspect that the engine is running hot.


If the cooling system fails the pressure test, then a completely new game plan is required.


The CEL (Honda calls it a MIL) lighting up is likely unrelated to your engine burping coolant. Do as advised by McLargeHuge and retrieve the error codes to find out what is causing the CEL.

True, I do not know for sure that it ACTUALLY overheated (I really hope not), but the gauge for sure went above normal. We first saw some smoke coming from the engine bay, I jumped back in and stopped it right away. As I was kinda stressed, I do not remember if the gauge actually touched the red line or not, but it was for sure right up there. Hopefully I got it on time. Seconds later some coolant leaked out.


Excellent, didn't know it was that easy to check engine codes yourself. Gonna check it out today, then I'll know for sure if it's safe to do a small trip or not. Thanks again!


FYI; I'm not a mechanic (only been working a little bit with car painting and spare parts logistics some way back) so forgive me for possible dumb questions. Might be lacking the correct words for some parts in my rather weak auto vocabulary.

 

[Honcho]

I had a head gasket that only leaked under hard load and the car otherwise drove completely fine. But in those cases, it burped coolant only under hard load, not while idling like you described. Therefore, I think there may have been a few air bubbles left in your coolant lines (based on your TB/WP service mileage it looks to have been recently done) and the hard running pushed them out. It would explain the behavior you described. Checking your coolant bottle for block gas would eliminate the head gasket possibility. If it comes back clean, then I would do a pressure test and then run through the bleed procedure a couple of times and see if any more air comes out.