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The only thing I can think of is that the coolant seal(s) is letting combustion gasses into the cooling system, thus pressurizing it. Sometimes, the coolant seal(s) can let pressure get past the seal from combustion, while not letting coolant flow the other way into the combustion chamber. Hope I'm wrong, but there is, IMO, no other means of causing what just happened to you unless the spring cap is not bleeding air out of the system like it should.
What should be happening is that as you drive the car, air in the system rises to the highest point in the system and then is let out under pressure through the spring cap. So, IMO, since this is repeatedly occurring, unless the cap is not working, you have a coolant seal issue.
The only thing I can think of is that the coolant seal(s) is letting combustion gasses into the cooling system, thus pressurizing it. Sometimes, the coolant seal(s) can let pressure get past the seal from combustion, while not letting coolant flow the other way into the combustion chamber. Hope I'm wrong, but there is, IMO, no other means of causing what just happened to you unless the spring cap is not bleeding air out of the system like it should.
What should be happening is that as you drive the car, air in the system rises to the highest point in the system and then is let out under pressure through the spring cap. So, IMO, since this is repeatedly occurring, unless the cap is not working, you have a coolant seal issue.
Thanks DaveW, this is the first time I am experiencing this. I have another cap (FC .9 bar) on order so will try swapping to see.
I refilled the coolant and removed a small amount of coolant from the reservoir to get it back to the Full mark. I went for a quick drive, under boost and no “Add Coolant” light or buzzer. No coolant overflowing from the reservoir. Fans come in and out as they should. I will allow the car to cool for the next few hours and see if I pull the cap again, if I have another coolant shower on my hands! Will report back.
I am hoping the cap is just old/bad, but I will see when I swap the caps this week. Once I get it in hand.
DaveW - is there a specific test or equipment I can do/use to verify if the coolant seals have gone bad? Thanks
...DaveW - is there a specific test or equipment I can do/use to verify if the coolant seals have gone bad? Thanks
Cheers
You can pressure test the cooling system as has been previously suggested. But if the seals are only leaking from the combustion chamber to the cooling system, that won't tell you anything. Something is causing a large amount of gasses to get into the system, and since you are not losing coolant, having steam out the exhaust, or hard starting, a pressure test may not show anything.
There is also a hydrocarbon test that can be done on the coolant. The presence of hydrocarbons would indicate combustion gasses getting into the coolant. If they are present, it would confirm a coolant seal failure.
Last edited by DaveW; 02-06-22 at 05:19 PM.
Reason: added hydrocarbon test
You can pressure test the cooling system as has been previously suggested. But if the seals are only leaking from the combustion chamber to the cooling system, that won't tell you anything. Something is causing a large amount of gasses to get into the system, and since you are not losing coolant, having steam out the exhaust, or hard starting, a pressure test may not show anything.
There is also a hydrocarbon test that can be done on the coolant. The presence of hydrocarbons would indicate combustion gasses getting into the coolant. If they are present, it would confirm a coolant seal failure.
Thanks DaveW. Appreciate the feedback. Will look into the hydro carbon test as an option.
I waited until the car fully cooled down and released the cap again. No coolant sky rocketing out. There was a slight pressure felt on the cap. Coolant reservoir was only about 2 tick marks above Full.
Inspected the cap in more detail and the seals seem a bit worn. Went back to the files and found I changed over to an aftermarket AST about 2 and a half yrs ago. So this cap has just been sitting for that time. Once I get the new cap I will run this “test” again then go from there.
Appreciate any other feedback / input from anyone.
Changed the cap to the FC style 0.9 bar, wayyyy easier to take off and on lol. Started up the car and it idled and went for a very short drive to ensure everything was up to temp. Parked the car overnight and tried releasing the cap about 24hrs later. No coolant attacked me or spilled out from the filler neck and only some air came out and coolant level was not full but at a decent level. I will be testing again to see if the issue was the cap.
While driving today, the coolant buzzer and “add coolant” light came on. Then went away after about a minute or two. Coolant temps were in the normal range. Fans on and off as usual. I will let it cool and then recheck the levels at the filler neck a few hours from now. Not sure if this is a coincidence or the issue continues. Maybe I will bleed the system again for the 5th time lol.
Also hearing a slight vac leak by the upper intake manifold. Will be doing a smoke leak test soon to try and pin point the location. Not sure if that has anything to do with the coolant system issue.
After filling or having a lot of air in the cooling system, it's not unusual to have the low coolant warning a time or 2 until all the air works its way out of the system
Yep, everything you described sounds normal …other than POSSIBLY the buzzer. But I agree with DaveW, it’s likely just a little air pocket. It’s also normal for the coolant level to drop slightly when you remove the cap. If it’s a good seal and complete cold, there should be a slight vacuum under the cap which holds the coolant level up in the filler neck. When the cap seal is broken mine always drops an inch or so, just below the overflow nipple.
After filling or having a lot of air in the cooling system, it's not unusual to have the low coolant warning a time or 2 until all the air works its way out of the system
Thanks DaveW, I went for a drive again after topping up after it cooled and no buzzer or light
@Sgtblue I did notice it drop an inch or so when I opened the cap and could hear like a suction sound before the cap would fully release.
As I mentioned I just drove the car and now it’s cooling down, then I will pop the cap again to see fluid level etc…
Thanks again for all your help, truly appreciate it. Hope this will help anyone going v-mount. Change your cap lol!
Further update: popped the cap and coolant came pouring out …the car was slightly warm but definitely cool enough to pull the cap.
I have a pretty loud vac leak somewhere in the mani. That I need to find. Could the leak be causing pressure to be built up in the coolant system ???
I have been researching bad coolant seals and the car has none of the “normal” symptoms - car starts easily first try every time , ZERO smoke out the exhaust, no champagne bubbles in the Lisle Funnel.
Every time I think I have this beat….nope
Going to do the following:
1. Hunt the vac leak and get that fixed using the smoker leak method
2. Do a hydro carbon test - kit is on the way
3. Possibly change the coolant reservoir hose just to be sure
Any other recommendations, happy to hear. Or is it engine rebuilding time
Also what’s baffling. Earlier I drove the car and the buzzer and Add Coolant light came on. Went back home and made the car cool down for 45-50 mins then released the cap, some pressure/air released but no coolant !! Topped it up and she was all good to go. Drove it again, no coolant light or buzzer.
BUT now when the car is cool…here comes the coolant again ….yesterday had the car warm up and then let it cool overnight, checked the cap this morning and no coolant !
Also what’s baffling. Earlier I drove the car and the buzzer and Add Coolant light came on. Went back home and made the car cool down for 45-50 mins then released the cap, some pressure/air released but no coolant !! Topped it up and she was all good to go. Drove it again, no coolant light or buzzer.
BUT now when the car is cool…here comes the coolant again ….yesterday had the car warm up and then let it cool overnight, checked the cap this morning and no coolant !
WoW!
Cheers
This combination of symptoms says to me that there are combustion gasses getting into the coolant. Otherwise, when you open the cap after running the car a few times long enough to get hot, but then letting it cool, only air should come out when the engine's cold or mildly warm. That coolant comes out under those conditions says gasses are getting into the cooling system somewhere other than the spring-loaded fill-cap vent. So the hydrocarbon test is in order to prove or eliminate whether a coolant seal leak exists.
Also, IMO, an audible intake manifold vacuum leak should have no bearing on the cooling system.
This combination of symptoms says to me that there are combustion gasses getting into the coolant. Otherwise, when you open the cap after running the car a few times long enough to get hot, but then letting it cool, only air should come out when the engine's cold or mildly warm. That coolant comes out under those conditions says gasses are getting into the cooling system somewhere other than the spring-loaded fill-cap vent. So the hydrocarbon test is in order to prove or eliminate whether a coolant seal leak exists.
Also, IMO, an audible intake manifold vacuum leak should have no bearing on the cooling system.
Thanks DaveW. I will be doing the hydro carbon test once I receive the kit. Will post up the results
I've heard that air pockets can act 'springy' and result in pressurized coolant when the engine is cold. I haven't seen this on my car, however. Try the Lisle funnel method again now that you have the correct cap. I sometimes leave the funnel nearly full overnight after flushing the cooling system. Also I dislike the OEM coolant overflow tank since you can't see much of what's happening. I sometimes ghetto-rig a 1L water bottle to a length of hose to watch how much coolant is getting vented and then confirm that the pressure cap is sucking the coolant back in as it should when the engine cools down.
I don't remember if anyone has mentioned this, but If you have air pockets in the system it will usually result in a 'water rushing sound' behind the center console when the air pockets make their way through the heater core. On my car this happened after idling for a while and then starting driving, I'm guessing this was from the change in water pump speed or from water sloshing as the car starts moving.
I've heard that air pockets can act 'springy' and result in pressurized coolant when the engine is cold. I haven't seen this on my car, however. Try the Lisle funnel method again now that you have the correct cap. I sometimes leave the funnel nearly full overnight after flushing the cooling system. Also I dislike the OEM coolant overflow tank since you can't see much of what's happening. I sometimes ghetto-rig a 1L water bottle to a length of hose to watch how much coolant is getting vented and then confirm that the pressure cap is sucking the coolant back in as it should when the engine cools down.
I don't remember if anyone has mentioned this, but If you have air pockets in the system it will usually result in a 'water rushing sound' behind the center console when the air pockets make their way through the heater core. On my car this happened after idling for a while and then starting driving, I'm guessing this was from the change in water pump speed or from water sloshing as the car starts moving.
Thanks scotty305, at this point, it cant hurt to use the Lisle Funnel again. Thanks for the suggestion with the coolant reservoir, might give that a try.
I don't have my heater core hooked up, AC also removed. Haven't noticed any "water rushing sound" inside the car, however, when the car is off after a drive, I still hear like air bubbles in the filler neck area. Maybe some air is still trapped in the system, not sure. Haven't heard anyone else have this experience.
Just a thought and throwing it out there......Would a filler neck like this help? Due to the design - AST type of setup, and the release cap. Prior to going v-mount, I had the Pettite Racing AST tank with a release cap (red "handle")....And when the car was cooling down after a drive I would normally release the red handle on the cap and could hear the air rushing to the coolant reservoir.
I am cautious that having the manual release on the rad cap could be masking any potential issues..... For reference this is the Vinny Fab kit from their website.
Those "Lev-R-Vent" radiator caps are pretty crappy. Thin metal. I've never been pleased with them.
OEM cap all the way.
That said, that aftermarket thermostat housing doesn't really do anything as far as adding functionality, it just replaces the ugly stock one with a shiny one. That's about it.
Those "Lev-R-Vent" radiator caps are pretty crappy. Thin metal. I've never been pleased with them.
OEM cap all the way.
That said, that aftermarket thermostat housing doesn't really do anything as far as adding functionality, it just replaces the ugly stock one with a shiny one. That's about it.
Dale
Thanks Dale. I haven't had any issues with them in the past, but just wanted to see what the community thought about this setup.
Hi, just a thought about the cooling system. Some of the aftermarket V mount radiators have the inlet and outlet on the top or the bottom, so check for that. It is not a good design.
If the radiator has the nipple on it for the 5/16 hose connect it to the nipple on the thermostat housing. The other nipple from the radiator cover housing should go to the overflow bottle.
If you could post a picture that will be ok.
Take off the radiator cover start and run the engine whilst keep fulling. when you raise the rpm slowly the water level should drop and the rise as you release.
Keep doing this until the level does not really move.
Let the engine cool down with the cover off and start again, then cover it off.
Don't overfill the coolant bottle.
With this you are equalizing the radiator with the engine and whatever gases build should go over to the bottle and make sure the overflow bottle hose is in the water and it can vent to atmosphere.
You could also open up on the highest possible hose in the system, I think it may be one of the throttle body hoses and vent there while the engine is running.
I am not making a guarantee suggestion but over the years I have tried some of these things. I am willing to know how it worked and any comments if I may not be right, thanks.
Hi, just a thought about the cooling system. Some of the aftermarket V mount radiators have the inlet and outlet on the top or the bottom, so check for that. It is not a good design.
If the radiator has the nipple on it for the 5/16 hose connect it to the nipple on the thermostat housing. The other nipple from the radiator cover housing should go to the overflow bottle.
If you could post a picture that will be ok.
Take off the radiator cover start and run the engine whilst keep fulling. when you raise the rpm slowly the water level should drop and the rise as you release.
Keep doing this until the level does not really move.
Let the engine cool down with the cover off and start again, then cover it off.
Don't overfill the coolant bottle.
With this you are equalizing the radiator with the engine and whatever gases build should go over to the bottle and make sure the overflow bottle hose is in the water and it can vent to atmosphere.
You could also open up on the highest possible hose in the system, I think it may be one of the throttle body hoses and vent there while the engine is running.
I am not making a guarantee suggestion but over the years I have tried some of these things. I am willing to know how it worked and any comments if I may not be right, thanks.
Thanks shaunrotor, i appreciate the suggestion. Willing to give it a try and see how it works out. The aftermarket rad kit I use doesn't have the nipple like the factory radiators. So I deleted my AST and run the coolant hoses like everyone else.
I will be bleeding the system again this weekend with the Lisle Funnel to see if any air pockets are still in the system and then once I receive the hydro carbon test kit, I will get that done as suggested by DaveW.
Bled the system again and there were a lot of bubbles coming out. Way more than last time. I squeezed the hoses as well and that helped to push some more bubbles out the system.
I did the procedure twice. Cold engine, warm up, cool down. All while the funnel was attached. Coolant reservoir is at the full mark or just over.
I did notice after I went for a spirited drive, I could hear NO air rushing thru the coolant hoses as I did in the past. Hopefully now I have gotten all the air out the system.
I will be doing the hydro carbon test once I get the kit, there has been a delay in shipping. Will share the results of that test as well.
Did the hydro carbon test and didn’t show anything really. It was the test that has the blue fluid and placing it over the filler neck and if the fluid turns yellow then exhaust fumes are present. However, I had mine not change the fluid color. But coolant started to get in the system after a few minutes. Turned the fluid green. Pic below.
Also did a coolant pressure test using a Mityvac system and one clamp was not tightened all the way on the radiator and saw coolant coming out. Tightened it down and did the pressure test again and it held for over 10 mins at 14-15psi.
Question. When the car is idling with radiator cap off the coolant starts to come to the top of the filler neck and about to overflow. Is this normal? Coolant temp was about 46-50 degrees C.
Should I bleed the system again or start pulling bolts to remove the engine?
…
Question. When the car is idling with radiator cap off the coolant starts to come to the top of the filler neck and about to overflow. Is this normal? Coolant temp was about 46-50 degrees C.
Yes, that’s absolutely normal. Overflowing coolant with the cap off and engine running is to be expected. The coolant is heating up and expanding. That’s what pressurizes the system when hot. With the cap on tight it would normally overwhelm that spring on the bottom of the cap and go into your reservoir. Sometimes called the overflow…sometimes called an expansion tank.
02-06-22, 01:02 PM
…the car was slightly warm but definitely cool enough to pull the cap. 
….yesterday had the car warm up and then let it cool overnight, checked the cap this morning and no coolant ! 
