1st Gen R53 Cooper S 02 S overflowing but not overheating?

:cornut: 1st Post, welcome to MA. I'm an R56 and not an R53 guy but, R53s are notorious for cracked thermostat covers. Do check it. Other R53 people should be along later.

Jason

 

R53 Cooling System Primer:

For 2002-2006 R50 MINI Cooper and R53 Coooper S Hardtops, and 2005-2008 R52 MINI Cooper and Cooper S Convertibles.

Thermostat

Thermostat begins to open at 89-92° C (192° F - 198° F) and is fully open at 103° C (217° F).

Expansion Tank Cap Cap pressurizes the system to 1.1 bar (16 psi) at which point the cap valve will lift to relieve pressure. If tank is split or cap can't hold pressure anymore, replace w/ Canton or RMW Tank w/ Stant cap. The Forge version still uses the OE cap. Here is a Canton/Stant combo pic:


Cooling Fan

Radiator Fan is a nine bladed fan measuring 400mm in diameter, driven by a 350 watt motor controlled by the EMS2000.

Low speed is switched on at 105°C (221° F) coolant temp and off when the temperature drops to 101°C (214° F).

High speed is switched on at 112° C (234° F) and remains on until the system coolant temperature drops by 4° C (7.2° F, so @ around 227F) at which point the system will revert to Low Speed.

The cooling fan will also operate on Low Speed when the Air Conditioning is switched on and system pressure reaches 8 bar (116 psi). Should the Air Conditioning system pressure rise to 18 bar (261 psi), the fan will automatically run on the High Speed.

If your low speed fan is dead, bypass the burnt green resistor.
Bypassing the Resistor for the 02 2plug version, here's what I did:
http://www.motoringalliance.com/forums/cooper-s-engine-drivetrain/15631-r53-rad-fan-resistor-surgery.html#axzz2u71aI6ot

For 03 up single plug fan version:
1. Unplug 3wire harness
2. Connect brown of socket>black wire's pin
3. Connect thin red/green of engine socket>fan's thick red
Get hi when low speed is supposed to kick in.

 

^^^^ well that really sums up what I was going say. (Good advice)

 

Had a friend who's MINI started doing that when his crank damper was starting to buy the farm. Might be worth a peek while your trouble shooting.

 

:cornut: DaveO cracks me up. Our very own Don Rickles. Gotta love him right?

Jason

 

It's not overheating. The expansion tank is a known weak point. They split. From the details in your post it seems as though your expansion tank needs to be replaced.

Options are OEM, it will happen again

Forge, uses the same cap as OEM and some say it's a bad idea. I've had it on there for 7 years with no problems. But I do carry a spare top since they will give up the ghost at some point.

Canton or RMW brands, these use an off the shelf Stant type "proper" radiator cap.

 

Replace the expansion tank and radiator cap. Most OEM tanks will last 7-12 yrs before they start leaking. Also check and/or replace the hoses below the tank while you're in there. If you want to up grade use an aluminum tank, type of cap is up to the user but I prefer the traditional caps because they are more common and easier to get.

 

Another big advantage to the Canton/RMW tank is the fact that the overflow tube can use a hose to direct the fluid to someplace that doesn't get all over the tank and other items.

 

Yep, another issue with the OEM tank, the cap dies. I keep a spare in my glove box.

A new cap would fix the issue.

If you want a long term fix replace the tank with one of the aftermarket ones. Replace the clamps too, Inspect the hoses, probably would not be a bad idea to change them too, depending on budget.

 

Replace the OEM garbage tank and gap and get a real metal one with a proper rad cap.

 

First....
I would replace the tank/cap....the new oem tank comes with a new cap...
If it fixes it..great...
One question....do you know if the cooling system was bleed properly? Can be a pain...but can result in the cooling tank overflowing...
The right level is not full...but to the seam (more or less).
Next....if it us still doing it...
Gets kinda $$....
Have heard of a few mini headgaskets going where the cooling system gets filled with exhaust..... More rare....
But the fact the oil cooler started to leak makes wonder if there was lots of corrosion from lack of coolant changes.....
As to "did I get ripped off"....I bet the weep hole on the pump was showing leakage...so 99% sure a pump was going to go soon...that is WHY the shop likely thought the pump was bad....

 

If the repair shop wasn't knowledgeable about MINI's they may not know there is a bleed valve that needs to "Burp" the air out of the high spot in the radiator hose...

It's pretty easy for you to do... The bleed screw is #5

 

Anybody know the part number for the correct Stant cap?

Edit: nevermind, Canton part number for the Stant cap is 81-030.