Hi all,

I have a serious problem.

When you start the car stone cold with the coolant cap removed, the level slowly rises until it overflows out the reservoir. Remember, everything is stone cold, not even warm yet.

My first thought was a blown coolant seal, as stone cold, after running it for a minute or 2 and opening the cap you get a sound of pressure being released and I could sware that once it smelled like unburned fuel.

What baffles me is that there are no air bubbles whatsoever, and if I switch the car off just before the overflow, the level remains stationary where it is. There is no gurgling or anything like that and the level does not return to where it was before starting the car.

Any thoughts on why this may be happening? Don't want to drop the engine and send it off for a rebuild if something else may be at play.

A clogged line maybe?

I'm stumped although I know these cars like the back of my hand...

Thanks.

 

maybe you should tell the back of your hand to let it overflow until it stops to then see what happens while keeping an eye on the temp gauge just to make sure it doesn’t overheat. It should just get up to temp idling without overheating with the cap off though, unless maybe you live on Mount Everest. Typically a 50/50 glycol mixture won’t boil until around 226*F @ atmospheric sea level.

 

Is the car on level ground? The overflow cap is not the highest point of the system, and with the thermostat closed and the engine turning you could easily be transitioning coolant from the heater core or other areas to the front through the return hose. With the cap on, the air trapped in the overflow needs to be compressed for coolant to move in there, but with the cap off nothing is stopping it.

You can test for exhaust gases in the coolant, its a pretty basic test if you can get the kit. You need to get it warm to see bubbles in the coolant, the thermostat needs to be open for coolant to actually circulate through the rad and overflow.

 

The car is parked on a slight uphill so the reservoir is the highest point.
I agree that the thermostat needs to be open for coolant to circulate. My thoughts are that maybe I messed something up with the coolant lines as I removed some to work on my sohn as the sohn reservoir was leaking.
How could I be getting overflow from the heater core to the coolant reservoir? When cold?

 

Yeah, I agree. No boiling going on, I don't get that far.
No overheating with the cap on, but it does spit out coolant when hot.

 

Through the lower return rad hose. Since nothing is actually returning through it, water is free to flow backwards if you pressurize the engine end (with heater core and all that). That pressure could be exhaust gases, thermal expansion or just mechanical pressure from the water pump.

Which hoses did you play with exactly? Did you burp the system after? I imagine some air would have gotten in?

 

It didn't give me a chance to burp it. Any way i got the reservoir hoses the wrong way around?

I need to go check but it's freezing, extremely windy and rainy at the moment.

The thing is that if it is air, there is no gurgling and the second you switch the engine off, the level will immediately stop rising and won't go back down, so that wouldn't be the case with thermal expansion, as it would still continue to rise a bit after switching the engine off.

It is as though the coolant is going from engine to heater core and then to the overflow, instead of going back into the engine.

 

Maybe we should remember that the coolant surge tank has a level indicator range on it and I’m fairly certain it is the highest point in the system. Otherwise it makes no sense for it to maintain the partially full level range if there is fluid sitting up higher that could flow back into it. There aren’t any check valves etc. that would prevent that once the engine is turned off from a warm state. You’re supposed to fill with coolant, then set the level by letting the engine run and warm to get the system in full circulation with the cap off, then seal the cap once the level is set.

Coolant blowing out after that is an entirely different issue, not so much an uncommon one either.

 

That's all correct. In my instance however you get nowhere near letting the engine warm up. Almost immediately starts to rise and slowly flows out the top. No bubbles.

 

Ok I have a promising update. I decided to take TeamRX8's advice. I.e. let it overflow and see what happens. Turns out it had a huge amount of air in there.

It overflowed to a point and then a huge amount of air came out and a huge amount of froth.

Turned the car off, it started gurgling, added more coolant started the car and the burping process went as normal, no overflow untill the car was well up to temp.

Freezing cold, rain and very strong wind stopped me from investigating further. Looking good however. I'm still not discounting a coolant seal problem at this stage. Fingers crossed.

 

It could be, but what was described is more than that. Now you can proceed with investigating further and tell the back of your hand I said “you’re welcome” 😆

 

Yeah, it was too good to be true.
More of the same today, overflowed when cold and let a lot of air out along with a lot of froth. I took the heater core out of the equation by bypassing it just in case it had a hole in it and introducing air into the system . Seemed to help.
Still while on the road it will overflow coolant, and when I put my ear close to the cap, I hear a constant hiss.
Air is getting in the system. I'm sure I have no leaks so my only thought is a coolant seal failure.

Here are the sequence of events that led to this. I was driving along when I went to pick up my son. It was dark. I smelt coolant and my bird cage symbol illuminated. I immediately pulled over, turned the car off and started to investigate.

Removed battery, battery tray to find that the upper radiator hose had torn, it was very brittle. In the meanwhile I had my 5 year old son in the street with me while doing the repair, so I had one eye on him and one on the car.

i cut the bad bit of the hose and connected it again. In my haste I accidentally broke the cooling fan connector. I didn't know it at the time. Added water and off we went.

We get to our destination and I turn the car off and my cooling fans were going mad for 20 minutes after shutdown. We are in winter, so they shouldn't be doing that.
To cut a long story short, since I heard the fans working, I didn't think that the fans were a problem and looked at basically everything except for that. Only one fan was working, the first setting never came on. So only at 101c the drivers side fan was working out of the 2, before that no fans.

Two weeks past and I finally found the problem. Up until then, no problems of overflow or anything like that. Whilst I had the battery out, I thought I'd tidy up my sohn etc l so I removed some coolant hoses as one of them had a slight bulge, cut it and re connected it.

Connected everything, glad that I got away with only one fan working without damage. Filled up the cooling system and here we are.

Just when I fixed the fans, this started...

 

Just trying to get my head wrapped around this. Are you monitoring coolant temps via a gauge at all, or is the 101C just because that's when the fan 2nd stage kicks on?

I'm willing to bet that with only 1 fan running and only on the second stage for 2 weeks, that coolant probably ended up getting waaay too hot.

 

Yes it did get very hot, I measured 107c at one point. It would only get very hot in slow traffic. When moving it was fine.

The needle never moved past its normal just below center.

 

Is 107 the hottest it got? Not great, but not terrible... *should not* have caused problems.

I would do a block test (chemical test for exhaust gas in the coolant)

 

I measured 107 at most, but I assume it went higher than that on 3 occasions as I remember reading that fans for a long time staying on after shutdown is when ECT is 110c and over.

The needle never moved, so I'm assuming that it didn't go over 115c.

There is something that I haven't mentioned. The car is equipped with LPG, so my last ray of hope, is that maybe the LPG reducer has failed and is letting LPG into the cooling system causing it to over pressurise.

My mechanic told me that when you see froth in the coolant, it is caused by air and coolant being whipped up by the coolant pump.

I agree with the test for exhaust gases in coolant, but no-one has those here. If LPG is in the coolant due to a reducer failure, then the test would give a false positive.

The car is not overheating, the fans come on at 97c and it drops fast. Yet it over pressurises.

So next step is to bypass the LPG reducer and hope for the best.

 

You keep saying it over pressurizes, but I’ve yet to see any data to back that up.

You do understand that once it’s shutdown there’s no flow, but the engine is still hotter than the actual coolant temp at shutdown, right?

So it could be rising up high enough boiling in the engine and then have an overpressure event. Or the cap is leaking before the pressure setting. Or the surge tank seat is leaking, and so on.

Mine use to blow off after a hard autocross run until I switched to Evans coolant. What does that tell you?
.

 

My engine has a definite coolant seal failure.
I bypassed the LPG reducer, and still it will over pressurise.
I have changed 3 radiator caps, I have bent the teeth on the caps to make it screw down tighter etc.
The reservoir stinks of unburnt fuel, you can see vapour coming out from cold, before the thermostat opens.
Coolant has a hard time getting to the heater piping as well. Probably due to combustion gases in the system that wont allow coolant to circulate.
Cold when I remove a coolant hose I get pressure released.
No leaks anywhere. White smoke on startup and the engine bogs when started cold for a bit and then after a short while works as normal.
I can still drive it like this, but when it comes to rebuild time, there won't be anything left of the coolant seal channel.
As I said, I know these cars like the back of my hand. In all conditions you should never even lose a drop of coolant. They don't build up a lot of pressure. Of course if you exceed a certain temperature, naturally you are going to build pressure in the system, but I can tell you that in 40c degree summer with air conditioning on and running LPG, for years I never lost a drop. Temps in summer going up hill I would see maximum 104c with the Aircon on.
I've had the coolant reservoir replaced as my old one cracked where the cap seats. It is not new and the plastic has worn quite a bit by removing and placing the cap back on several 50+ times. It is not cracked however. The pressure is being released at the overflow hose, nowhere else. The cap I have on there is a 1.1 and it screws down tightly with bent teeth and all.

 

Sorry to hear. Those aren't great signs for sure :/

 

somebody there can at least do a pressure check, right? It’d be a bit unusual to have a one-way leak. There weren’t any other signs going on before this, like idling issues on start up or coolant level slowly dropping?

 

I will do a pressure test. There were no signs before this apart from the top radiator hose that failed.
No idling issues whatsoever, still starts hot cold no problems.
Never lost a drop of coolant. Now it is sprayed out the overflow.

 

Here's a video of what goes on:

 

If the top hose is cold when fully warmed, your thermostat isn't opening. Or, anyway, there is no water flow through it.
Maybe that's what caused the failure in the first place.

The rise in coolant early on could be expansion of gas that's accumulated in the system since the last run. But either way, there is gas.

 

The thermostat is opening, otherwise it would overheat real quick. There is no overheating going on, so the thermostat is working correctly.
The top hose flows from the rear rotor to the closed side of the thermostat. It should always flow from cold. This is so you get hot air early on in winter through the heater core.
What I believe is happening is that gas fills the top hose causing an air lock. In any case, the engine needs to be pulled out to replace coolant seals. I think you agree?

 

My opinion is that when your fans weren't working the system overheated (I bet the engine saw temps way higher than you monitored) and am willing to venture a guess that you have a coolant seal problem.