Coolant level keeps dropping on the verge of giving up - MINI Cooper Forum

First Generation Faults & Fixes MINI faults and fixes 2001 - 2006

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post #1 of 16 (permalink) Old Apr 16th, 2017, 07:35 PM Thread Starter
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Coolant level keeps dropping on the verge of giving up

As the title suggests I am regularly topping up the coolant as the level keeps dropping - its a 2003 Mini Cooper S.

So far I have changed the following on the coolant system:
- new expansion tank cap
- new thermostat & housing inc gasket
- new heater matrix
- new radiator
- new water pump (as this leaked when I pressure tested the system at 4 bar)

The expansion tank isn't showing any signs of leaks. I haven't done a further pressure test, a bit concerned I may break something else if I take it up to 4 bar again - at 2bar nothing happened last time.

I have also refurbished the cylinder head, and fitted a new head gasket and also replaced the oil heat exchanger with a replacement from ebay. I do get a bit of moisture in the rocker cover but I believe this is condensation, as I usually only use 1-2 times per week for a 6 mile run into work, or taking the kids into town - and also you can see water droplets on the oil cap, not the mix you would expect if the leak was at the head gasket still.

I have done so much work on the car and spent a fair amount of cash I really don't want to give up on it, but want to cure the leak so I can take in on another 2-3 trackdays this year.

Struggling to find any more answers, but wondered if anyone else had found a miracle cure, or if the problem could be something deeper in the engine and might need a engine swap to cure. Anything people, any ideas welcome!

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post #2 of 16 (permalink) Old Apr 16th, 2017, 08:18 PM
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Originally Posted by aim82 View Post
As the title suggests I am regularly topping up the coolant as the level keeps dropping - its a 2003 Mini Cooper S.

So far I have changed the following on the coolant system:
- new expansion tank cap
- new thermostat & housing inc gasket
- new heater matrix
- new radiator
- new water pump (as this leaked when I pressure tested the system at 4 bar)

The expansion tank isn't showing any signs of leaks. I haven't done a further pressure test, a bit concerned I may break something else if I take it up to 4 bar again - at 2bar nothing happened last time.

I have also refurbished the cylinder head, and fitted a new head gasket and also replaced the oil heat exchanger with a replacement from ebay. I do get a bit of moisture in the rocker cover but I believe this is condensation, as I usually only use 1-2 times per week for a 6 mile run into work, or taking the kids into town - and also you can see water droplets on the oil cap, not the mix you would expect if the leak was at the head gasket still.

I have done so much work on the car and spent a fair amount of cash I really don't want to give up on it, but want to cure the leak so I can take in on another 2-3 trackdays this year.

Struggling to find any more answers, but wondered if anyone else had found a miracle cure, or if the problem could be something deeper in the engine and might need a engine swap to cure. Anything people, any ideas welcome!
did you have head pressure tested when it was off,, if not could very well have a cracked head,, what kind of head gasket did you replace it with, ie metal layer or composite,, i always use the second and a descent make.

,
Classic Range Rover Blown Head Gasket Cooling System & Cylinder Block Repair | eBay i used this stuff a few times had a sierra cosworth with water problem cracked head used this stuff car was still going strong 18 months later.. very very important point the water jacket must be totally clean, i flushed it over a week. used dish washer liquid and kettle cleaner and dishwasher cleaner, kept starting car up to temp leave over night drain it use something else,, then finally clean water rinses a few times.. might need to repeat it every so often. or head off get crack tested,, will prob find crack around number 4 cylinder as this is where they seem to go as cooling system is a tad stupid airlocks and pockets give hot spots that crack,,

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post #3 of 16 (permalink) Old Apr 16th, 2017, 11:35 PM
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...or take the head off and inspect it.

Was it skimmed and inspected for cracks??

Does the car smoke

I would take her for a good long HARD!! DRIVE if it's just moisture it should disappear.

I suspect it's a warped/cracked head or ****** HG


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post #4 of 16 (permalink) Old Apr 17th, 2017, 11:08 AM Thread Starter
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The head was pressure tested and rebuilt by a reputable engine builder so fairly confident ok, HG replaced with composite Victor reinz, no smoke etc. I think i probably still have a coolant leak somewhere, but changed so much already. Any ideas on a safe pressure to test cooling system at - enough to show leaks but not enough to break anything?
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post #5 of 16 (permalink) Old Apr 17th, 2017, 11:27 AM
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The head was pressure tested and rebuilt by a reputable engine builder so fairly confident ok, HG replaced with composite Victor reinz, no smoke etc. I think i probably still have a coolant leak somewhere, but changed so much already. Any ideas on a safe pressure to test cooling system at - enough to show leaks but not enough to break anything?

one bar is 14.7 psi at sea level 4 bar is 58.8 psi
Car Combustion leak tester head gasket 30ml. fluid, 15 tests Free P&P 1st class | eBay
,
your only option now is do a sniff test buy this off ebay this will tell you without any doubt if carbon monoxide is in your water jacket. if it is then you know then its inside engine,, one other point i have in past had heads tested and came back ok fitted it got a problem as most places test them cold or warm and not at 80-98 degrees where car engines run at with added pressure of 4 cylinders and supercharger increasing pressure,.
another option is running it on water free coolant, or a stronger mix of antifreeze helps due to water boils before antifreeze will so dont expand as much.. ie the sniff test comes back clear run it up to temp and switch off and check everywhere including heat matrix and floor carpets etc, if comes back with carbon cracked block maybe..

one point when you put head back on did you clean out all the head bolt holes in the block with some kitchen paper roll. so no oil or water in them,, i have seen people forget and do head bolts down start the engine and it cracks the block as the liquid in the holes expands with heat,, or ie liquid oil comes out of holes it contaminates the head gasket and allows it to blow past when engine gets to temperature, as head gaskets go through a chemical change when they get to temp the first time
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post #6 of 16 (permalink) Old Apr 17th, 2017, 08:04 PM Thread Starter
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Thanks for the tips, I'll try the sniff test. The head bolt holes were cleaned out, but i don't know if i was that meticulous. I suppose i also thought that because my oil level wasn't rising by the 50-100ml i am putting in every week then i wasn't getting water into the oil.
One comment from another forum, could i be overfilling the expansion tank by continually topping back up to max each time when cold, max being the top of the internal wavy mouldings in the expansion tank?
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post #7 of 16 (permalink) Old Apr 17th, 2017, 10:02 PM
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Thanks for the tips, I'll try the sniff test. The head bolt holes were cleaned out, but i don't know if i was that meticulous. I suppose i also thought that because my oil level wasn't rising by the 50-100ml i am putting in every week then i wasn't getting water into the oil.
One comment from another forum, could i be overfilling the expansion tank by continually topping back up to max each time when cold, max being the top of the internal wavy mouldings in the expansion tank?
The expansion tank should have MAX & MIN marks on the side.

Cooper s expansion tanks are renowned for splitting.

Get her up to temp and watch the expansion tank and cap, they shouldn't leak



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post #8 of 16 (permalink) Old Apr 17th, 2017, 10:45 PM
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If you take it for a longer run what does the temp gauge show? Steady or does it rise? Put the heater full on which will help if it is getting too hot when you test it.
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post #9 of 16 (permalink) Old Apr 18th, 2017, 03:05 PM Thread Starter
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The tank does have max min marks, but the tank is so yellowed i cannot see the fluid through it, but the max seems about the same as the top of the internal wavy mouldings. No sign of leak from tank or cap at temp previously but will check again.

As for temp gauge, it always stays steady in the centre, never seen it rise above centre even on two track days. Plenty of warm air from heater. I have been keeping the system filled with coolant though to prevent any overheating issues.
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post #10 of 16 (permalink) Old Apr 18th, 2017, 03:33 PM
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Thanks for the tips, I'll try the sniff test. The head bolt holes were cleaned out, but i don't know if i was that meticulous. I suppose i also thought that because my oil level wasn't rising by the 50-100ml i am putting in every week then i wasn't getting water into the oil.
One comment from another forum, could i be overfilling the expansion tank by continually topping back up to max each time when cold, max being the top of the internal wavy mouldings in the expansion tank?
expansion tank has marks on it no should never be over filled this will not allow the water content to expand with heat and burst pipes and radiator or heat matrix

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post #11 of 16 (permalink) Old Apr 19th, 2017, 12:38 AM
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Sounds like a poorly fitted head gasket! Did they reuse the original head bolts??

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post #12 of 16 (permalink) Old Apr 19th, 2017, 02:10 PM Thread Starter
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New head bolts used, new gaskets etc. I also did a compression test about 2 wks after the rebuild and all cylinders were equal and over 150psi, so getting a good seal around the cylinders, so assume a good seal between oil and water ways. Looks like next steps are to monitor coolant level and see if it continues dropping below minimum level, if so repeat cooling system pressure test, then move onto sniff test when it arrives.

I am getting a bit bored of it now, i want to move onto improvements but won't until the basics are fixed.
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post #13 of 16 (permalink) Old Apr 19th, 2017, 06:11 PM
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New head bolts used, new gaskets etc. I also did a compression test about 2 wks after the rebuild and all cylinders were equal and over 150psi, so getting a good seal around the cylinders, so assume a good seal between oil and water ways. Looks like next steps are to monitor coolant level and see if it continues dropping below minimum level, if so repeat cooling system pressure test, then move onto sniff test when it arrives.

I am getting a bit bored of it now, i want to move onto improvements but won't until the basics are fixed.

i have seen water pumps that when car is sat running dont leak then drive them they leak,, if your engine has high pressure in header tank its only going to come from one place,, ie cylinder to water jacket, sniff test is only way forward with it,, having a plan if it does come back positive is a good idea,, black ink dye in the water before you strip it can help find the crack or faulty gasket if it is.. run it as long as you can before with it in the water drain the water leave it to dry out for a day before stripping it,, any black dye lines will show leaks in the gasket.. this works some times depending where its leaking
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post #14 of 16 (permalink) Old Apr 20th, 2017, 02:15 AM
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Have you checked the heat exchanger (oil cooler) as they have been known to crack as you may be loosing coolant from there. you will need to pull the front right wheel off and the wheel liner to be able to inspect it correctly and its not a difficult job to remove it if it need changing.
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post #15 of 16 (permalink) Old Apr 20th, 2017, 07:55 AM Thread Starter
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I changed the heat exchanger out 2-3 months ago for the same reason. However it was a used item from ebay and I did use the O-rings that came with it - not brand new.

I put mains water pressure (about 1bar) on it before fitting and there was no leak into the oil side, however knowing what I know now (coolant system runs at higher pressure) I wonder how relevant that was. I will have a look to see if any external leaks first, but may look into getting a new replacement, or repeat the cooling system pressure test with this part disconnected from the engine.

Another few hours stripping the car down to investigate....

Any thoughts on the recommended cooling system test pressure???
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