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post #1 of 7 (permalink) Old Apr 24th, 2019, 09:11 PM Thread Starter
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2005 Cooper facelift - coolant woes - any ideas?!

Hi All,

From the UK and recently purchased a facelift R50 Cooper as a cheap run-around and project.

Car on the whole is generally v sound, has fairly good (though not complete) history and has only covered 78.5k miles.

Love the car and have sorted a number of its minor problems but I have one big one I am really struggling to sort.

The car generally runs and drives OK, hasn't outwardly demonstrated that it's tried to overheat at any point, the stage 2 fan definitely kicks in...but.....it keeps losing coolant from the thermostat housing cap. It tends to weep slightly from the cap and when hot, light pressure on the cap tends to cause hot coolant to flow out from the seal and run out the bottom of the car. Seems to be affected more by the incline it is parked on. If I park it on my steep driveway nose up it doesn't really drop other than maybe a slight weep. Parking nose down it tends to pee out.

Now as to what's been done.......

First noticed a problem when going to fill up the washers. I noticed the expansion tank was more or less bone dry (having been very full previously) and the lid had popped open. Can only assume the coolant was forced under through the thermostat and out through the expansion tank. I knew this wasn't normal. I therefore changed the thermostat cap. Note the cap that was on it was not original, v v tight and I suspect the rad would have blown before it would have vented any coolant if ever!

Following the cap change, no more issues with coolant coming out of the expansion tank but now losing it from the thermostat cap as described above.

Car goes to friends garage, diagnoses lazy thermostat. The stat, housing and cap are all renewed. Expected it to be fixed but soon presents the same exact issue.

I have two theories...but am leaning more towards the 2nd.

1. There is an airlock in the system still (despite being bled) causing pressurisation and for the coolant to leak from the thermostat cap. Note I can hear some glugging from behind the dash indicating there may be some air in the heater matrix at least...but the heater does work just fine.

2. The head gasket is probably goosed. Would explain the coolant pressurisation. Strangely though the coolant doesn't seem to be becoming in any way contaminated and not noticing any mayo in the oil filler or on the dipstick. The car does however run rough on starting from cold or if not run for a period of time (which if it's not fouled plugs could well be coolant in a cylinder I guess).

My mate it a top flight mechanic, but he does seem fairly adamant it's not the head gasket but my gut feel is it most likely is. He hasn't really been able to replicate the symptoms I've described but I don't suppose it's been left on an incline of any sort whilst with him and that could well be the difference?

I've suggested perhaps parking it on an incline and also doing a compression test.

Does anyone on here have any ideas...given the rad cap and thermostat and housing have all been changed, also the rad is quite new and it's integrity has been checked that most will probably say head gasket?

Appreciate any thoughts or comments anyone may have......frankly it's driving me spare!!

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post #2 of 7 (permalink) Old Apr 25th, 2019, 04:34 PM
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could buy head gasket sniff tester off ebay link below. can also buy dye you add to coolant and run then use a ultra violet light to find leaks, this will also show up on end of exhaust system and within the oil filler cap if any water has escaped, i do this all the time when get strange water car faults.. the tritec engine is a proper pain in arse to bleed takes ages keep adding water very very slowly, parking car facing up hill then down hill can help when bleeding them,, i cheat and use a pressure tool to pressurise the system and bleed form pipes and jubilee clips,, ie release and allow any air out,
ultra violet dye link below
https://www.ebay.co.uk/itm/Ring-Wate...IAAOSwusdb~Os2
ultra violet light link. after using on cars could solve murders in your spare time ie detects blood
https://www.ebay.co.uk/itm/LED-UV-Bl...zeDSkcz6hbSVAQ
head gasket sniff tester
https://www.ebay.co.uk/itm/BT-3-BLOC...UAAOSwLEtYi8Gi

if have gasket problem this stuff is best out there to seal it done a few cars over the years not seen them back,, use it as a end of life car treatment as such,steel seal,,, important must follow instructions to letter
https://www.ebay.co.uk/itm/STEEL-SEA...kAAOSwEzxYPERF


Albert Einstein: The definition of insanity is doing the same thing over and over and expecting different results.
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post #3 of 7 (permalink) Old Apr 25th, 2019, 06:26 PM
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Head gasket failure doesn’t always mix oil and water, if it’s gone between a bore and a water way the sniffer will tell you (plus the pressurisation of the tank and hoses - which will be rigid).

When the car is cold remove the expansion tank lid, if there’s pressure then it’s likely to be exhaust gas. Do not do this when the car is warm.
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post #4 of 7 (permalink) Old Apr 26th, 2019, 11:47 AM
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Quote:
Originally Posted by k3fus View Post
Head gasket failure doesnít always mix oil and water, if itís gone between a bore and a water way the sniffer will tell you (plus the pressurisation of the tank and hoses - which will be rigid).

When the car is cold remove the expansion tank lid, if thereís pressure then itís likely to be exhaust gas. Do not do this when the car is warm.
pressurisation of the tank and hoses - which will be rigid). there is another process like this its when there is a airlock bubble in the the top part of head around the exhaust ports side,, works a bit like a boiling kettle ie boiling kettle only boils from the metal heater element inside it, same sort of thing happens where the head gets hot spots due to lack of coolant due to not being bled correctly,,, and cause boiling at the point where the water is this causes a lot of pressure from steam,,, so very important coolant system had been bled correctly,, if still doing it removing the thermostat and lock for air bubbles coming out of head tank works as long as bled correctly,, and the tritec engine is a royal pain in arse to bleed

Albert Einstein: The definition of insanity is doing the same thing over and over and expecting different results.
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post #5 of 7 (permalink) Old Apr 26th, 2019, 06:28 PM Thread Starter
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Thanks for the replies folks.

I'm starting to wonder if it is just air in the system that's been causing the problem.

I know it had a new rad in recent times and likely wasn't bled v well. Wondering if the coolant loss may be the air gradually finding its way out under pressure and forcing coolant from the pressurised cap on the thermostat?

Absolutely no sign of coolant/oil contamination....also system has been pressure tested with no loss of pressure detected. Also since my mate has had it, couple of days) it's not rough started once hot or cold or by all accounts leaked/lost any coolant. Also no funny smells from coolant tank or from exhaust to suggest contamination.

I can open the overflow tank when cold and absolutely no pressure at all and in fairness to the car it's not yet overheated once. It just seems to have developed a proclavity for leaking coolant from the thermostat cap when parked on a slope, more so facing nose down than up which I feel is odd and might be air pressure related.

Still at the garage so hopefully will know more next week.
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post #6 of 7 (permalink) Old May 15th, 2019, 02:49 PM Thread Starter
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Hi folks, been a while but I thought I'd post how this ended up being resolved in case it helps someone down the line.

Transpired the following caused the underlying issue: -

* Lazy thermostat - looked as though the thermostat had gotten a bit lazy and was opening a little too late. The thermostat, housing and cap were all replaced (came as a kit).

* Bad thermostat cap - Big lesson I learnt here....dont skimp by getting a cheaper OE grade pattern part here, go to Mini and get the real deal. Both the Febi Bilstein cap I purchased and the one that was supplied with the kit were garbage. these caps did not seal properly even with the new thermostat housing and just allowed coolant to pour out as it started to get pressurised. Whilst the Febi cap was all but identical on the outside bar the lack of the BMW part code, internally neither the spring or rubber seal were as good. Needless to say once the BMW cap was fitted it sealed a treat and no more problems. Was a little surprised as Febi parts are supposedly normally very good....maybe I just got a bad one but still not worth mucking about with.

* Broken 1st speed cooling fan - resistor switch was replaced (rather than entire fan assembly) and all was good.

Bar the fact the cooling system was still harbouring some air despite having been bled thoroughly; the car then ran perfectly. Could see some minor bubbling and a raising of the coolant in the header tank which by all appearances seemed to be the car gradually purging the air.

Ironically despite going to all that effort to get it fixed I no longer have the car......sold it for a very late facelift 06 plate Cooper S, with Chilli pack and LSD. Really liked the Cooper, found it alot of fun and was very endearing to drive quickly as it went well for an NA 1.6 petrol and seemed to enjoy being revved, but the S is a whole other level. Tepid vs Hot hatch for sure........cant believe I've waited so long to own one, they are fantastic!
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post #7 of 7 (permalink) Old May 15th, 2019, 03:17 PM
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the febi bilsteen ones i have used a lot never had a issue with them, that said there are Chinese versions on line that are not febi bilsteen as china loves to copy stuff as cheap as poss, i know cant take nothing for granted these days,
and yep the cooper s is by far the better car for driving

Albert Einstein: The definition of insanity is doing the same thing over and over and expecting different results.
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