Hi folks - I'm working out the two final tweaks on my build - tie rod replacement (the seemingly ONE thing I didn't change - grrr) and an overheating issue. Regarding the latter, I've bled the system as best I could, and the car runs just fine for about 5-10 minutes, Afterwards, it overheats to the red zone in a matter of seconds. However, if I crank up the heat all the way and restart the car, it cools right down again and I could drive it forever with the heat maxed out (an awesome feature on a hot summer day...)

Guidance is SUPER appreciated! Also, shouldn't there be an audible warning when it overheats? I get one for not wearing a seatbelt but nothing when the darn engine is about to explode - not super helpful when the only view in line of sight is the tach.

 

Leaning towards the thermostat possibly failed. The heater hose that sends heat to the interior runs directly off the water pump, circulates through the heater core and back to the rad. The engine itself has to pass through the thermostat after the water pump, circulates the engine then back to the rad. It's sounds like the first one is happening and the second is not.

If you do see about replacing the thermostat, I highly recommend getting the URO Parts aluminum thermostat housing (available on rockauto). It will outlast the car for a cheap price!

 

Perhaps that's it - but I installed a new one with my build when replacing the head, and added an aluminium housing as well. It was a MAHLE / CLEVITE off Rockauto, and I researched the brand for these and saw good reviews. That said, certainly could be faulty out of the box and wouldn't be my first with Rock Auto parts. I also replaced the fan resistor since those are prone to failure and the water pump.

 

If you changed the thermostat it's possible that it was installed backwards, with unfortunate results.

 

as mentioned above its also possible, secondly the vent/breather hole must face up.

Just based off the issue I can't see what else it would be, unless there is an absolute blockage. Mahle is a solid brand, could very well be a defect. I have a Rein in mine, 10,000km no issues.

Defects can happen, installed a brand new OEM BMW water pump last year. The same 10,000km and it's leaking out a weep hole... this is the only recommended water pump to get, needless to say I will be trying aftermarket manufacturers now!

 

Thanks all - I triple checked that the hole faced up and it was installed correcty, but won't hurt anything but my time and a few bucks to swap it and see what that does. I'll start there.

 

As a last thought does your fan work? And is it kicking into high speed? I believe high speed is about 112° C (234° F)

Unfortunately there is no audible warning, there is a red overheating light and thankfully a gauge to actually watch the temps unlike most cars.

Have you driven it in this state? And does it stay cool while moving by chance?

 

High speed kicks on. But unsure about low - i.e. how to check - and if that could cause these symptoms... Running the AC does not engage the fan, should it?

 

It could cause the symptoms per say, but once the high speed kicks on if there is coolant flow it will lower the temp rather quickly. You can run 12v to two pins on the fan connector to test low speed, easily accessible. You can pull 12v from the airbox wire lead, and ground to the transmission mount. Breif video below

I don't believe the AC changes the fan, just adds a slight drag to the engine really and may drop rpm once first engaged.

 

Nice, thanks

 

Well I found one review of the Mahle thermostat when purchasing a Rein. Maybe it IS the problem: I have always been fine with Mahle and Behr products, this thermostat is absolute trash. Went through my engine supercharger cooling system etc and got it up and running and chased overheating issues for 2 weeks nightly, thinking it was a head, head gasket or air in the system. Finally agreed to take the thermostat out and check it in boiling water, sure enough, stuck closed will not open. Bought oem, oem one opens and closed 3 times in the time I left this one in the water and it never opened. It has brass and copper parts that are not centered, totally different design than oem. Also left brass shavings in my thermostat housing that I had to flush my system of. Don’t waste time and money on this.

 

Haha what a review ! Let's hope that's it, Rein is the most ordered thermostat through RockAuto so I wish you the best.

Also cool write up on your car, your a little further into engine work than I've got. But I did buy mine with a blown motor, bought 2 "parts" cars and swapped engines. Basically have 3 to keep one going lol. This coolant nightmare never seems to end, I'm glad you've elimated the thermostat housing failure though!

 

Hey thanks. Waiting for that final celebration post once the kinks are worked out. Parts minis are super cheap now so good call on your build approach! I'll let you know if your reco fixes things

 

Also if using AC your power steering pump should kick on just a few seconds after starting AC. If it doesn't I believe the low speed engine fan will not kick on and heat will rise fast!

 

It never hurts to chemically flush the system to clean out all the old gunk. I realize you have a new thermo and rad but the engine block itself could be adding to your problem. A flush is easy to do. Use only distilled water (approx. 3 gallons at <$1/gal. at Walmart). Collect the drained liquid in the gallon jugs you just emptied and a local oil change location will usually dispose of it for free. Good luck.

 

Temp sensor (or the connector / wires) Something to check if not thermostat


https://www.northamericanmotoring.co...t-working.html

 

Ha!
I was going through the exact thing you are for 2 weeks, that is my review. I was pissed! FCP now took it off their site. I figured Mahle/Behr was the right choice, I kept telling myself no it’s not the thermostat but everything pointed to the thermostat. I finally tested it and the ***** never open, and it ended up getting metallic flakes in my cooling system. I took it for the first hour or so ride after my rebuild and all was good, after that nothing but overheating. It’s a different design and i think it opened once and then closed and that was it, never to open again.

 

Chili, which one is the behr?

 

The one with the black gasket is stamped MAHLE

 

What makes me refuse to put my reading glasses on when they're right there around my neck?

 

That's too funny you wrote the review! I just landed from work travel and will swap it out this weekend. The brass shavings thing sucks so I may flush the coolant (again) as well. Another $20 and mess to deal with added to the list.

I really hope this is the problem and, if so, am pretty dang peeved a faulty design from a trusted brand has kept me from completing my 7 month project. I'll have some choice words and will let the company know what's going on.

 

Yes the one with the black gasket is the mahle, you can see the center piece is not perfectly centered. The white gasket is the oem with 130k miles that was still working but I wanted to replace while I was there, stamped with a Chrysler emblem. I got a new oem and was instantly back in service after a quick bleed.

 

Well I tested the Mahle thermostat and the Rein multiple times in boiling water. Guess which thermostat is the POS one that won't open?



With the Rein installed I drove it 30 minutes straight and no problems. It has the same design as the Mahle which is different than OEM but at least it works. We'll see if it stands the test of time.

 

Glad you got this worked out. I also bought an aftermarket thermostat when i was rebuild my R53 and it ended up sticking open and throwing a code for underheating. I bought a new OEM one and have been fine since. Personally, I will never not buy the OEM one moving forward.

 

I am very glad you got it fixed, yippy! Like I said my Rein is above 10,000km and working well. Let's hope your luck continues forward and your not revisiting this again soon.

Cheers!