I'm having an issue with my 2004 R53 and need some thoughts on what it could be. The car is pushing coolant out of the expansion tank and of course causing it to spike in temps.

Car was purchased last year after the previous owner ran it hot. Put a new head on it along with gasket, etc. Car has been doing great for the past 6 months and 2000 + miles.

Car has 63K miles, has new radiator, electric water pump with new thermostat, new expansion tank with new cap, system has been properly bleed.

There is no oil issues (no coolant in oil), coolant is nice and clean as well, no smoke at start up or any other symptoms of head gasket failure. I have ran out of possible causes.

Any thoughts? Thanks

Bob

 

Going to move you to the Stock Problems/Issues section.

What temp is the car running at? Is the fan running?

 

When car is acting normal, the temperature stays just below half on gauge. At times, the temp will temporarily spike for about 3 seconds and then drop back down. I have correlated the drop back to normal with the 2nd stage fan kicking on. And yes - both stages of the fans work.


I assume the 1st stage only works with AC on or when car hit a certain temp?

Bob

 

To confirm, the coolant is exiting the expansion tank through the cap, not the center seam or hoses?
And the tank is filled to the proper level - to the max line, even with the center seam?

If so, it's possible that you have a bad cap. I recently had an overheating episode that ended up being a bad cap (also on a newer tank), and when I replaced it, it no longer overheated.

The stock temp gauge unfortunately is not of much assistance when trying to diagnose overheating issues. If you can somehow link into your system via a laptop or smartphone via an OBDII dongle, you can more accurately see what's happening with the coolant temps.

If everything else checks out, maybe look at the electric water pump.
Why are you going the electric route and not running the conventional OEM water pump off the supercharger?

​Fan/Thermostat Specifications:​​
Thermostat is wide open at 196°F.

When engine first comes up to temp, you should see the thermostat cycling, from 196°F to 189°F and back up again, until the temp rises beyond. If it's not cycling, you have a faulty thermostat.

Fan Operation:

Let it idle while you watch the temp come up.

At 221°F the Lo-Speed Fan comes on, then turns off at 214°F
Hi-Speed Fan comes on at 234°F
If 239°F and no fan, turn engine off.

 

Replaced the radiator cap and same results. The original expansion tank has been replaced with a metal one so yes, the coolant is being pushed out through the cap area.


The car had the electric water pump on it when I bought it. Had a mechanic check it out and he said it was working as it should be.


The only thing I can think is that the head gasket has developed a leak which surprises me at 2000 miles after replacement and the car has been run hot since the replacement. If it needs another head gasket job I will just dump it and let someone else take on the project.


I hate it as this is a fairly low mileage Monte Carlo Edition so was planning on keeping it a while but not putting any more high $$ into it.


Bob

 

To confirm whether that's the case, head over to your local AutoZone (or similar), and they should have a Block Tester that you can borrow. That will test for the presence of exhaust gasses in your coolant. Make sure you get the test fluid.

 

May try that this afternoon.


One other thing I noticed - I can drive the car at highway speed and it spikes about every 30 seconds but I can park it and let it idle (even after driving on highway) and it will never spike. It seems to only do it during driving.

 

That makes me wonder if your electric water pump is doing it's job, not pumping enough coolant to keep the temps down..