My wife's 05 R53 overheated and I initially thought it was the reservoir tank. It needed some other work and the oil pan gasket needed changing as well.
I changed the:
Water pump flange and oring
water pump
thermostat and gasket
Serviced the supercharger
oil pan gasket
intake air duct gasket

The car still overheats. I can let it sit and it will be ok. I get to driving and it starts heating up, kick on the heater and defrost and that cools it down a bit.

Any thoughts? I don't see any signs of a head gasket leak.......

 

My thought is if your heater core is enough to bring it down a bit, your radiator may be having some problems. Sucks that its not possible to remove the radiator cap and peak down in there to see what it looks like. That or the fan motor is struggling to spin fast enough.

 

Any way to test to verify it is could be the radiator. am kinda at a loss....and I wouldn't think a head gasket would cause the overheat as it does, it isn't lacking water until the pressure cap starts to open....but I am open to any suggestions..

 

Have you verified that your radiator fan is running. The R53 has to 2 stage fan, the low stage starts around 212 and the High around 230. The Lowspeed stage routes the power through a resistor (mounted on the fan shroud) that quite often burns out, so you loose the low speed. which causes the engine temp to hover above 230. If you run the AC it kicks in the High speed fan and brings the temp down to normal. Check the easy stuff first....

 

I do hear the fan running full bore when it is close to overheating. One does kick on as well as it is sitting and idling after it has ran for a while......

 

You have to make sure the cooling system is bled to get the air out of the system. If not done, you will still have overheating. I had a bad Coolant Tank, replaced and over heated again. I thought must be Thermostat...replaced and happened again (and this was in the summer on the I-10 on the way home from work so a lot of traffic). I found out after the fact that you have to bleed the system, once I did no more problems. There are YouTube videos how to do it...not hard.

 

So, I watched the video again to be sure I did not miss anything.
I topped it off with water (ill swap it with antifreeze when I get this figured out)
Started it, reservoir cap off.....put heater on and fan on low
Finally warmed up, cracked the low *8mm) bleeder till I saw a steady stream of water...closed that
cracked the radiator hose bleeder and waited and waited and waited and waited......only way to get water to come out is to close the reservoir cap, but after some water would flow, I would close it, then wait a few secs, open it and just tons of air......then after a few mins of me trying to bleed it (reservoir cap closed) water started backing up outta the reservoir tank cap (maybe no tight enough, but still no water from the bleeder

 

To be honest, I never did the lower bleed screw. I figured air wants to escape up and only did the top screw. I did it late summer 2019 and haven't had an issue since!

 

Ya, funny why with the res cap on and the bleeder on the rad hose is cracked open....hot water is backing up out of the res tank cap and the bleeder has nothing but air

 

Wasn’t sure because the list of parts includes the oil pan gasket but not the coolant tank. Was a new reservoir tank and cap installed too?

This was an interesting issue regarding a new thermostat which could easily be overlooked in further troubleshooting since a new thermostat was just installed. The “old” reference in the post and pic is a new broken thermostat being compared to second new thermostat:

https://www.northamericanmotoring.co...ml#post4527432

 

Yes, put a new res tank and a new cap on there as well.

 

In order to get the system up to temp so that the thermostat opens, I recall you have to have the system closed up, meaning coolant cap on while you bleed from the vent ports. I only used the one on the top radiator hose to remove air.

When you were trying to bleed the system, were the fans cycling? You should have heard the low speed cycle on/off before the coolant tank started to overflow. Also, is your power steering fan working? It's also in the electrical circuit of your radiator fans.

 

So I filled the system back up with water and started the car, let it run for a bit, bled both bleeders. Then I put the cap on the res tank and bled the system again......then shut the car down (after idling for 30 mins or more) temp stayed constant.......let it cool down, topped off res tank.
Fired it up again and let it idle......no issues ( no fans either)
Drove it around, sure enough, started to heat up, got it back into the driveway.......and jumped out and cracked the front bleeder (nothing but air)

Thoughts?

 

Sounds to me like you still have air stuck in the system. Are you filling it just through the tank? I like to take the top hose off and fill the radiator directly, and sometimes I’ll even fill through the top bleeder screw.

 

While you're using the top bleeder, try squeezing the top hose to help 'pump' coolant around.

 

Yeah, its hard to get coolant in that tiny bleeder hole, but if you have a Cajun Injector (basically a big syringe for injecting turkeys, etc) you can use that as a funnel...don't inject coolant into a turkey

Honestly, it sounds like you got a dysfunctional thermostat. You can toss it in a pot of boiling water to see if it opens. I got a new one once for my Jeep TJ that didn't work. Had me stumped for quite awhile. Maybe the reason you can't get the air out, that t-stat isn't opening to allow the water to move to push the air pockets towards the bleeder. Also could be why its backing up out of your expansion tank.

 

Bad Thermostats happen more than you would think...sad

 

So I did try using a nozzle and filling the system up from the front bleeder (engine completely cold and cap off the res tank) until the water was literally coming out of the res tank. Let that settle to the correct level (draining some to get it back to "max level") put the cap on, fired it up,,,,,,,, after a while, it heats up to "norm" temp...I bled the system till only water was coming out......It still eventually starts to heat up, then the fan comes on and water usually likes to come out of the res tank at this point.....

 

So, I installed a new expansion tank on mine last night. Filled the tank. Filled the radiator hoses using the bleeder valve, got it up to temp with everything open (bleeder and tank), put the in cab heater on low, let it spew and spit radiator fluid all over for a minute or two, put the expansion tank cap back on, left the bleeder open. Let it spew until it was just water coming out. Closed it. Revved the engine to about 1800 RPM for a few seconds, opened the bleeder, air came out, revved engine, opened bleeder, little more air, repeated...no air. Drove to the gas station to fill-er-up. Didn't even act like it wanted to overheat. Ran fine with the AC on. Got home, let it cool for about 2 hours. Opened the reservoir...reservoir was empty. Filled it half way, put cap back on, ran it around the block a couple times. Parked it. got up this morning, added a tiny bit of coolant (I mean, like an ounce or two). Sending it.

I think your new thermostat is bad. I ran mine with air still in it in South Louisiana with the AC on and it didn't overheat.