17 replies to this topic

[Madrugada]

Hi everyone, In this unprecedented hot weather here in Spain, my poor old Mini is getting very hot. I have done everything I can think of, flushed the cooling system & no sludge came out, fitted new head gasket just for the hell of it, no emulsion in the rocker cover which is a good sign, I checked the ignition timing, no pinking or over-running. The little car is actually running really well but is always on the point of boiling. Has anybody got any other ideas? I have thought of fitting an electric fan alongside the traditional yellow blade fan, do you think that might help? I would really like to hear of anybody else's experiences & solutions. Many thanks. John

[mbolt998]

I've also been chasing cryptic apparent overheating issues (in hot weather...).

 

You can try an uprated radiator and/or fan. There are various options available on Minispares and Moss.

 

There can also be question marks over the gauge and sender unit. You can remove the sender and dunk it in hot water to see what's what. On mine 90C is in the middle, where it should be, but 100C (sender sitting in a boiling kettle) is already halfway to H. I suspect that isn't right. There is a calibration on the gauge that I think sets how sensitive the H side of the gauge is. I haven't tried doing anything with it.

 

Do you have an IR thermometer? One of those gun things you can get off Amazon. I would be very interested to know what temp your cylinder head actually is after a typical drive (leave the engine running). Mine is normally about 107C or so. I am not convinced this is really a problem. The one time it did boil over (unrelated-- the fanbelt snapped), I stopped, waited 20m, and drove a mile or so home. It was 130C at that point. I don't think it boils over until 130C or 140C.

 

I believe the power of the cooling system is proportional to temp difference. So if it's 30C outside rather than 20C you will see an extra 10C on the gauge under normal conditions. In my case that's halfway to H.

[Spider]

When flushing the cooling system, I have found just flushing it with fresh water or the off the shelf 'radiator flushes' don't do much. I found CLR works well and use that for many years. Recent, I found a locally made commercial product that works even better, but both of these take around a week to work their magic. If there's any rust, no matter how slight, in the cooling jacket of the head / block, it does have a big impact of how well the cooling system can work. Fill with coolant after a proper clean, but if mixing your own from concentrate, only mix to 30 / 70 ratios (if using a gycol based type) as glycol isn't a good thermal transmitter, but does help thin the water and loose it's surface tension in those proportions.

 

As also suggested by mbolt above, check your gauge against something known, all too often, they are out (and can be a long way off).

 

If there are no faults with the cooling system, then adding an auxiliary radiator maybe all it needs, a core from a heater works well here, or as also suggested by mbolt, a bigger capacity radiator. I wouldn't bother with an electric fan, unless you find yourself stuck in traffic often, otherwise, it'll just be an impediment to the decent air flow the mechanical fan can offer.

[mbolt998]

If there is rust in the cooling jacket of the head/block (I'm pretty sure mine has some...) is there any way of getting rid of it?

[Homersimpson]

What type of fan does the car have?  The plastic ones have a right and wrong way to fit them (I can't remember about the multiblade metal ones if they are the same)

[Spider]

If there is rust in the cooling jacket of the head/block (I'm pretty sure mine has some...) is there any way of getting rid of it?

 

CLR will remove it to a point but not necessarily all the way, though if you change the CLR a few times, it will. It seems to remove so much rust, then loose it's 'zing'. If you do use this product in this way you'll want to leave it in about 4 - 7 days each time.

The product I have been using of late is Liquid Intelligence. It's a locally made product and I have found it very good, though it seems it's not available in other countries.

[mbolt998]

 

If there is rust in the cooling jacket of the head/block (I'm pretty sure mine has some...) is there any way of getting rid of it?

 

CLR will remove it to a point but not necessarily all the way, though if you change the CLR a few times, it will. It seems to remove so much rust, then loose it's 'zing'. If you do use this product in this way you'll want to leave it in about 4 - 7 days each time.

The product I have been using of late is Liquid Intelligence. It's a locally made product and I have found it very good, though it seems it's not available in other countries.

 

Thanks! I'll experiment with something like that-- it can't do any harm. If I take the head off (and change the head gasket) is it possible to get a decent look at the state of things inside there? Is this worth doing for the purpose of trying to clean things out? (Sorry to OP for hijacking his thread-- he already changed his head gasket!).

 

I didn't bother with any products like that because I thought they were mainly for cleaning the radiator core, and I replaced that anyway. Didn't realize they could clean out the head/block as well.

Edited by mbolt998, 16 July 2023 - 08:16 AM.

[Shooter63]

If there is rust in the cooling jacket of the head/block (I'm pretty sure mine has some...) is there any way of getting rid of it?

Yes it's called Oxalic acid also known as deck cleaner, you can buy it in crystal form, you mix up around 50g into water put it in the rad and run it for a few hours then drain the system by removing the bottom hose, flush the system with clean water, if you're still getting rusty water in the rad do it again but always flush with clean water, if you have a block tap fitted use that as well to drain the system. Once you have it clean use only distilled or RO water plus a maximum of 25% anti freeze, that should keep your water nice and clear. Oxalic acid will not clear sludge only rust.

Shooter

[Spider]

I think you'll see more and enough if you pop the thermostat out and look at the cooling jacket from there. That's a pretty reasonable indicator as to the rest of it.

[Madrugada]

Well, what can I say, Massive response & great help, thanks guys! Good advice with the electric fan, Spider, I'm sure it would impede airflow & the noise, I guess, would be horrendous! It was just a case of desperation thinking of that. I have a digital thermometer, but It's way off, it reads around 80º on all four cylinders & I reckon it's way over that! I think I'll invest in a better thermometer. Does anybody know roughly what it should run at? There doesn't seem to be anywhere to calibrate it so I can't rely on that. I'd never heard of CLR, I just used a proprietary flush agent from the garage, I'll try & find some, possibly on the internet. The car has a new heater matrix, so I can discount that. I'm guessing I'll research uprated fan & radiator as I cannot find any other reason for this problem. Maybe it's just GLOBAL WARMING! Thanks again guys.

Edited by Madrugada, 16 July 2023 - 09:30 AM.

[sonscar]

If you use descaler/rust remover be aware that the core plugs can leak shortly afterwards.Failure of one of these is not ideal.Steve..

[Madrugada]

Yeah, I just read on internet that CLR isn't recommended for descaling car engines for that reason, the last thing I really want is leaky core plugs!

[Madrugada]

Hi again folks, I'm still battling this 'overheating' thing and I don't think it is overheating at all. I got a new digital thermometer & I tested it out on a pan of boiling water & it read sort of between 95º and 109º (centigrade that is), you know how they bounce about without a definitive reading. OK, so I ran the Mini up to 'operating' temperature & checked the temp on all the cylinders on the head near the spark plugs & it was reading somewhere near 80º, I left the rad cap off & water was flowing out of the overflow at a fair rate of knots, I run it like that for ten minutes & it lost a litre of water. When I finally stopped the motor, the rad was still looked full! I left it to cool & sure enough the level in the rad went down to the tune of around 1 litre (that's a lot). Now please tell me I'm not losing the plot, Am I too old for this? I've had Minis all through the seventies through to the eighties & then my daughters had them into the nineties & I've never come across anything like this......it's weird. Is it possible to have an airlock? I've not heard of this before, but I'm clutching at straws! Somebody out there must have come across this before! I always found that Minis were always simple to work on, especially the standard 850s with HS2 carbs, totally without modification ( except electronic dizzy). The engine is in fantastic nick with beautifully unmarked bores, totally flat head & top of block, oil pressure is at around 90 even when it gets as hot as it suggests! I think I need a new water temp gauge as it goes straight over the H limit as soon as it has warmed up......that doesn't help. So, come on guys, get your thinking caps on! Cheers!

[Madrugada]

By the way, if I run the car with the cap on the rad, it seems to run normally & then when I stop the motor it chucks a fare bit of water out of the overflow pipe.

[Madrugada]

OK, I guess everybody is the same as me & have no clue.................it's weird!