9 replies to this topic

[jamesmpi]

Need some advise…
Last weekend at L2B my Mpi overheated just as I was parking up at Brighton. Switched off immediately and opened the bonnet to see expansion tank was “full” and could see large amount of bubbling. The fan was running fine before I switched it off and coolant temp was normal. I live 30mins away from Brighton and so drove straight there at normal road speeds

The car has been off the road for a couple of years but I’ve driven it quite a few time before L2B with no issues

Drove it home later than afternoon. Everything was normal.
Got 10mins out of Brighton, saw temp start to rise slightly, immediately pulled over and could see high levels of coolant in expansion tank and bubbling.
Left it to cool for 45mins and continued to home (about 20 minutes driving). Got home and check straight away and everything was normal. Temp… coolant levels… No sign of any bubbling.

I’m thinking exhaust gasses are getting into coolant system so possibly head gasket issue. Did a head gasket leak test and no sign of fluid changing colour indicating gasses present in coolant… but I know these aren’t 100% reliable

What else could it be? Failed water pump? Thermostat works, got hot air blowing from unit in the cabin and I know the matrix is fine as I changed it a few years ago. Coolant is nice and pink but will change it soon. Oh and the expansion cap is new too. Proper one, not cheap EBay

I don’t really want to take the head off unless i really have to. Any ideas??

https://ibb.co/FVnX1hd

Edited by jamesmpi, 14 June 2023 - 05:17 PM.

[Quinlan minor]

Before doing anything drastic, check the pressure cap and the header tank.

The header tanks are very prone to springing leaks, if the system isn't pressurised , the coolant will boil. That doesn't mean it's overheating and it definitely doesn't mean "exhaust gasses are getting into coolant".

There'll usually be a telltale if the Header tank has a leak, see below?

 

 

 

Attached Files

•  Header Tank Pin Hole 2 (small).jpg   30.33K   0 downloads

[jamesmpi]

Good shout but it’s fine. Replaced it a few years ago for genuine one.. but I do wonder it the tank as ballooned slightly under pressure.

It’s quite probable that the cap is bad too but it’s only a year old and bought it from mini spares

Before doing anything drastic, check the pressure cap and the header tank.
The header tanks are very prone to springing leaks, if the system isn't pressurised , the coolant will boil. That doesn't mean it's overheating and it definitely doesn't mean "exhaust gasses are getting into coolant".
There'll usually be a telltale if the Header tank has a leak, see below?

[Quinlan minor]

I'm on my third, or fourth, since '09, all 'Genuine'.

Next one is an alloy, if MiniSpares ever stock them again, or an ex-Volvo one.

[lappie]

Had this problem even with coolant caps from mini suppliers. Either wouldn't hold pressure and boil or would vacuum on cooling down and collapse the top hose.
Cured by using a Febi branded cap for a r50 MINI from ebay.
The plastic of the febi cap is much more rigid and actually seals.

[jamesmpi]

I have just purchased a brand new BMW Mini expansion tank cap (one with the blue rubber seal)

Will take it for a drive tomorrow to see what happens 🤞🏻

Had this problem even with coolant caps from mini suppliers. Either wouldn't hold pressure and boil or would vacuum on cooling down and collapse the top hose.
Cured by using a Febi branded cap for a r50 MINI from ebay.
The plastic of the febi cap is much more rigid and actually seals.

[Steve220]

A big thing with the MPi is people over filling the header tank too. Often they're filled to MAX. It needs to sit between min and max ideally. A new tank and R53 tank cap should put you right.

[68+86auto]

Not saying this is your problem but I saw a simple way to test for combustion pressure in the cooling system without test equipment. I was watching a video (not about a mini but a truck) and one of those chemical test kits didn't show anything so he put a rubber glove instead of the radiator cap and it inflated proving there was in fact a combustion leak.

 

I have a cooling system pressure tester which can be used for the same test, when my minis head gasket blew as soon as I increased the rpm above idle the pressure built up quickly.

Edited by 68+86auto, 13 June 2023 - 03:51 AM.

[jamesmpi]

Good idea. Might give it a go

Not saying this is your problem but I saw a simple way to test for combustion pressure in the cooling system without test equipment. I was watching a video (not about a mini but a truck) and one of those chemical test kits didn't show anything so he put a rubber glove instead of the radiator cap and it inflated proving there was in fact a combustion leak.

I have a cooling system pressure tester which can be used for the same test, when my minis head gasket blew as soon as I increased the rpm above idle the pressure built up quickly.

[jamesmpi]

So I took the mini for a couple of local drives after fitting a new expansion cap from MINI (used on an R53)

Seems to be behaving its self. Temp gauge is spot on in the middle. Periodically stopped and popped the bonnet. No sign of the coolant completely filling the tank and bubbling. But I did notice the coolant level drops slightly from the max line to about 3/4 full, but returns to normal once the engine is off.

Also did another sniff test after the first drive (and left for 20mins to cool to allow the cap to be safely removed) and it was fine.

So will monitor it and hopefully the new cap has sorted it

Edited by jamesmpi, 17 June 2023 - 03:54 PM.