44 replies to this topic

[Chris M]

Hi all . I have refitted my engine after but if a rebuild & tidy up but now it seems to boil up .
During the rebuild I replaced shells & bearings. Fitted a new swiftune cam & a ported head. All new gaskets & seals. The head gasket was a coper type which I was a little unsure if using but I did. From my experience it’s almost like it’s getting gases in the coolant system as the water level also rises. I removed the thermostat & seems to be better. Any help or advise would be great.

[CooperKid]

I had this with my MPI once it was restored. Turned out to be the black cap on the expansion tank. The coolant system on the MPI is highly pressurized and there is a valve in the cap and if that fails (may have accidentally dropped it or knocked it when the engine was out) the system will boil before the fan can kick in.

 

The expansion tank and cap would be my first suggestion before you look into a new radiator.

 

Perhaps there may also be air in the system somewhere. A flush and refill could sort that, but i would not recommend using a hose as the pressure is to high in that and you could get another/new airlock.

[Chris M]

Thanks strange you say that but I have heard hissing from the cap at times. I’ll get a new one ?

[CooperKid]

Thanks strange you say that but I have heard hissing from the cap at times. I’ll get a new one

The good thing is the caps are the same on the K-series metro and Rovers. Fortunately at the time we had a 1997 Rover 214Si Rally car so was just a quick test to change over.

 

I would be very surprised if its the rad if all was fine before and there is no significant damage to it.

[Chris M]

I’ve fitted a new expansion bottle cap & ran it up until the cooing fan cuts in twice. Didn’t boil over but the coolant level does rise from the max & nearly fills the bottle. When I turned off the engine & let cool down lots of bubbles kept coming up!?

[CooperKid]

As it has a return pipe into the expansion tank it is likely it will go above max until the engine has stopped and water has settled.

 

My next suggestion then is an airlock somewhere in the system. Run it until warm with the heater on full and hot so the water gets round, then drain and refill slowly.

 

Before you changed the cap was the fan kicking in before it boiled? Also what is the car temp gauge saying when this happens?

[Chris M]

I’ve ran the car several times now & sure there is no air lock & heater gets hot. The temp gauge is in the middle & cooling fan cuts in. Fan didn’t always cut in before it boiled before I changed the cap but seems to now.

[CooperKid]

Hmmm...

 

I'm not sure whether the expansion tank itself could cause the issue. If there is a tiny crack in it somewhere up top (so it wouldn't necessarily leak), may mean its not preasurising properly.

 

If your stat is still out, I would put that back in. Maybe get a new one if you have doubts about that one. Due to the electronics and fan switch, I would see if that now makes a difference with it back in and the cap replaced.

 

Try running the car up without the cap on, then gently squeeze the hoses feeding into it to see if any bubbles come out when its starting to get warm. If you are sure there is no air lock in the system, the next things would be:

 

Expansion tank itself

Rad change (maybe a flush through of that alone may help if any dirt/debris has got stuck in a small channel

Head gasket - Not the most favourable change but actually one of the cheapest. I've never personally had a problem with the copper gaskets. I know people who did a few years back but i believe that was a bad batch. If you do change the head gasket again, go with the BK450.

 

Out of curiosity, where did the new cap come from? Its not unheard of for there to be new/cheap ones that aren't up to scratch too 

 

Its very much one of those trial and error scenarios im afraid.

Edited by CooperKid, 28 June 2019 - 10:15 PM.

[Chris M]

Thanks mate. I got a new cap from euro car parts.
I’ve driven it into work this morning for an mot & drive fine . I checked it when I got here & all ok. Level ok?

[Jaffa cake]

Hi all

Just seen this thread, have a similar problem myself.

Have a 1998 cooper, fully restored by previous owner.

Drove across London last Friday, all good, went to the garden centre round the corner and there was steam coming out from under the bonnet! Left it and spoke to the prev owner, who said he'd had no problems but to let it cool then run for 10 mins to see if there are any leaks. Did that, added coolant no leaks, all good. Drove back across London on Thursday (an hour) all good.

 

Then today, Saturday drove my 2 sons to meet family, 30 mins journey, all good, but steam from under bonnet on way home. Pulled over, lots of coolant in road, realised expansion tank was empty, topped up once cooled a bit, ran again, no leaks seen anywhere, drove home, 10 mins. Steam coming out again. She's now parked up fine but I've no idea what's going on! No leaks, radiator is new but coolant boiling over, a blockage somewhere? 

 

Sorry for long winded version, but thought some back ground needed. Probably a simple-ish  answer from someone who knows what they are talking about, but a worry for me.  I'm hoping it' just a expansion vessel cap as mentioned above, as all else seems good. MY son's girlfriend's dad seems to think it might be head gasket! Don't like the sound of that!!

 

Thanks in advance 

[Chris M]

The water pump started leaking today ? it’s knly just over a year old!

[CooperKid]

Oh dear! That sounds like your problem then!
A dodgy impeller could have contributed to the over heating issue if water wasn’t circulating quick enough.

Highly recommend getting the updated water pump with the larger impeller. Minispares sell them and I believe they come with 3 years warranty. Shouldn’t be more than £20

[Chris M]

I carried out a combustion test with a kit I bought were the fluid turns from blue to yellow. Well it turned a green sort of colour? So in my book somethings not quite right. I removed the cylinder head tonight & found some pitting in the head gasket ? the gasket is a copper type.

[CooperKid]

Did you have the head skimmed?

Get a BK450 black gasket when refitting for sure and change the water pump as a precautionary

[Chris M]

The head hasn’t been skimmed. I checked it with a straight edge & all looks ok. I’ve got a BK450 head gasket & a new water pump.
I’m convinced the copper head gasket is the cause of the problem.