E46 Fanatics Forum banner
1 - 7 of 7 Posts

·
Premium Member
Joined
·
10,745 Posts
Thermostat I bought is bad, go get OEM part
* Do a long drive and then stop car and while idling, reach down and feel the lower hose in your hand; warm, cold, hot?

* I somehow think the issue is not the Tstat. put old and new ones in water pan and cook them. Watch carefully to see when it start open and notice the water temperature. If they opened way before boiling (70 or 80C) then they are no good. They should start open just before boiling, around 97C.

* How did you bleed the thing, in detail steps?
 

·
Premium Member
Joined
·
10,745 Posts
slowly add coolant into ET with bleeder screw out. Add coolant until coolant coming from bleed screw is solid (no bubbles) with heater on high temp, low fan. Suctioned out excess from ET to get between min and max. Drove the car a couple miles, let cool down and checked level, had to add a tiny bit, less than a cup.
I don't see at which point the bleeder is closed -- before or after the excess coolant was removed?
 

·
Premium Member
Joined
·
10,745 Posts
Just boiled the old thermostat, it worked just like it's supposed to :confused: Opened just before boiling
Maybe the Tstat electrical heater is turned on all the time and causing the Tstat to open too early. Test drive again with the Tstat 2-wire connector removed.

Recently replaced thermostat after car wouldn't keep @ temp, monitoring from OBC highest I would get was around 86 degrees C (it's been cold here in Seattle).
I also noticed I was overheating so now I'm thinking WP.
I'm a little confused here. Display shown coolant temp was 86C (not hot enough) and engine was overheated?

So with the Tstat confirmed working properly in boiling water and having reported 86C coolant and overheat issue, I think you might want to try with the Sapote bleeding method:

Sapote method, rev1:
1) engine cold, car head up on slope driveway or flat ground level is fine.
2) remove bleeder and tank cap, fill coolant to the MAX marker on the tank using the red rod as indicator. Do not overfill to top of tank.
3) close the bleeder, set heater to hot and fan low, run engine at idle. Don’t turn off engine until the end. Important: Do not let engine running more than 7 minutes total while the tank cap is not closed, to avoid damaging the cylinder head.
4) Crack open the bleeder to let air out and close it when no more air bubbles. Top off the tank to MAX marker. Close the bleeder and screw the tank cap by one turn to avoid coolant shooting in next step when rev-ing up the engine.
5) Rev it up to about 2500 RPM a few times to push out any air pockets (in the head and the heater core) into the upper hose/tank. Keep engine idling for next steps.
6) Crack open the bleeder again to let air out and close it when no more air bubbles. Top off the tank to MAX marker. Close the tank cap.
7) Test drive and check for having heated air in cabin. Done.
 

·
Premium Member
Joined
·
10,745 Posts
I would first get a genuine, or borgwarner thermostat. Another friend of mine bought 3 new mahle units, all of them were faulty. Swapped it out with a borgwarner unit, all works as expected. I suspect the electrical heater in the mahle thermostats does not work as intended
But OP also have engine overheat issue, so the Tstat heater part cannot be blamed for this. How could one has 86C running too cool while also has engine overheat issue? So must be air pocket in the system.
 

·
Premium Member
Joined
·
10,745 Posts
This made me wonder. Have you ruled out the fan being on (or on full speed) all the time? On the manual cars it should only come on when needed, commanded by the DME. If you have INPA there's a test you can do where you tell it to spin at 0%, 25%, 50%, 75% or 100%. If you step through those with the engine off you'll be able to hear when it's on (or you can get out and check) and the pitch will increase with speed. Or you could just start the car with the engine cold* and make sure it isn't spinning.

*question to fellow fanatics: would the AC need to be off too?
If AC is on, then the front fan automatically turned on, so for the INPA test then I think the AC should be off.
 

·
Premium Member
Joined
·
10,745 Posts
My concern is it’s taking too long to get up to temp and not all the way. No code yet, so maybe I’m wrong.
Too long to get up: how many miles from cold engine to what final temperature?
Did you do test drive with the Tstat heater wires disconnected?
The Tstat passed the boiling water test, and this is manual tranny so no failed auto tranny Tstat that causes slow coolant heating up. Maybe the elec fan turned on too soon due to bad lower hose sensor? To test, disconnect the fan connector (near upper right of radiator) and do a test drive to see if anything change.
 
1 - 7 of 7 Posts
Top