my thermostat in my 2003 R53 needs replacing, but before i order the new thermostat & dig in
i was wondering what else i might find or need to do this job (one & done)
should i replace the housing & bolts?
is there anything else i should look out for? (i remember reading something about old crumbling t-joints?)
should i use the "MINI/BMW" recommended koolant or not?
any help/suggestions will be appreciated

 

Use the factory thermostat , gasket , & BMW coolant ; check that the plastic T- housing is perfectly flat on a piece of glass .

 

Are you putting the aluminum thermostat housing on in place of the plastic housing?

As an owner who replaced an engine due to a cooling system failure, I don't trust the old, plastic cooling system components at all. Have you ever replaced any of the hoses in the cooling system? If not, I would recommend going "all in" and replacing all the hoses and tees. There are brass and aluminum tees available so you can eliminate the plastic once and for all.

Doing all of this is a huge job in that tight engine compartment. I took advantage of replacing the hoses and tees while my engine and transmission were out of my car after that tee broke on me.

That's just my $0.02.

 

+1 coolant system refresh time (if you haven't already)

 

i changed out my thermostat & housing on my R53, but my kar is still over-heating
any ideas?

 

Ideas:1) New thermostat defective. Not opening. 2) Air pocket. Not fully bled after thermostat change. 3) blockage 4) head gasket

 

Bleeding the R53 Mini Cooper S (2002-2006) cooling system requires removing air from the thermostat housing and the top radiator hose, ideally with the front end jacked up to make the cap the highest point. Run the engine with the heater on high, fan low, and reservoir cap off, opening the screw on the top radiator hose until a steady stream of coolant flows

 

did the koolant system bleeding thing, a few times .........and i'm still having an over-heating issue

 

For anyone preparing to do a coolant system refresh;
Here is a link to the that can replace the factory (prone to fail...?) plastic coolant hose connections.
An aluminum top purge hose connector replacement can be found at O'Reilly.
I had found and purchased an aluminum expansion tank "T" connector off eBay a while back.... I cant seem to find that link in my bookmarks - But here is a link to the expansion tank to heater hose ' T ' connector found on eBay.



Hope it helps someone in their search for "better than factory"/alternative to plastic - coolant hose connectors.

EDIT: If I recall - I think that ECS Tuning now sell brass coolant hose connector replacements as well.

 

How old is the Mini waterpump & are you running the BMW anti-freeze , because anything other then factory formula can cause overheating?

 

Do both upper and lower radiator hoses feel hot and approximately the same temperature? If not, bad thermostat or blockage somewhere in the system.

 

Are you sure the thermostat is not put in backwards? I believe this is physically possible but could lead to overheating since it won't open.

 

• Installation: Clean the sealing surface thoroughly. Position the new thermostat with the bleed pin (jiggle pin) at the 12 o'clock position to prevent air pockets.

 

it's the original water pump (no noises or leakage)
and yes i used the correct koolant

 

i thought that too (2nd guessed myself) .......so i took it back out to make sure, yes it was installed correct (no flipage), so i reinstalled & blead the system again

 

what kind of blockage? it's a closed system, what could get in there to cause a blockage? and if it was a blockage, where would the common blockage spot be?

 

she's not my primary kar, so I'm not pressed for time & want to properly correct the problem issue
hey guys, i want to say thanks for all your help & ideas
as this issue has me baffled, so I'm still digging into it

 

You suggested one possibility on your initial post: Crumbling T-fitting or the possibility of a casting flaw that has broken loose and blocked a passageway in the block or head. Suggest you investigate a reverse power flush of the cooling system and see what comes out.

 

Sorry for intervening - but I felt that @NC TRACKRAT has an interesting idea. I was wondering if "back flushing" the coolant system might force any obstruction/debris up into the overflow reservoir? ...OR better still - un-do the lower hose?
I'm not too coversant with water cooled engines but have done all the work on my Mini over the past 15years.
This discussion is of great interest to me.

 

i think if you remove the thermostat, its an open system. Water can move through freely

 

Yes, this is true. Will run too cold without the thermostat, though, so the ECU will never sense enough engine temperature to switch to a warmed-up running state. Probably will throw P0128 and possibly P0125 as well....

 

Were you having overheat issues with the thermostat you removed also, or just since you replaced the thermostat?

To see if your thermostat is working, you could take it out and put in water as you heat it towards boiling to observe if and at what temperature it opens.

 

thanks, I just thinking of checking the old thermostat as well, as maybe my overheating issues wasn't originally a bad thermostat as i thought
now on my to-do-list (i didn't do nothing progressive with the MINI overheating issue over the past rainy weekend anyway)

 

Overheating can also be caused by the coolant system not holding pressure. This could be something simple as a radiator cap gone bad or a failing head gasket. Without pressure the coolant boiling point drops significantly.

Obviously the Mini doesn't have a radiator cap but depending on being it the R50 or R53 you have a thermostat cap or coolant tank cap.

Check the rubber in the cap. Pressure testing the system might also give you some answers.

 

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