Hellppp overheat and interm. Heater

[razo-s.supra]

Good afternoon everyone! SOLVEDDDDDDDD**

Symptoms after swap-
Temp rises close to the 3/4 mark then drops to right below the 1/2 mark. It does this over and over again. about 3-5 minutes between each temp fluc. cycle. While the temp is at its normal operating (right before 1/2) the heater is nice and hot! When the temp starts rising to 3/4 I lose cabin heat until the cars temp drops back down to normal then the heater returns hot again. I have tried putting the front of the vehicle on stands to bleed the system and no luck.
The chances of it being a BHG seem low as it ran perfectly at 1/2 mark right before pulling the engine from the donor car (let it idle for 30 + min before driving and still maintained proper temp). There is no white smoke, no leaks, no milky oil, no smelly coolant (exhaust smell)

Details on the car.
-1987 325e
-m50nv swap (i pulled from the donor car
-late model I.E. radiator
-e36 expansion tank (waiting on late model e30 tank from awdbob)
-spal puller fan
-new metal impeller water pump
-new tstat 81*
-currently running straight distilled and water wetter
-no mechanical fan
-no a/c

[MyE30]

based on your description it definitely sounds like air bubbles in your coolant system.

[razo-s.supra]

based on your description it definitely sounds like air bubbles in your coolant system.

That is what I am hoping for. Just looking for anyone that has experienced this and has had a specific method used to alleviate this issue. Something I havent thought of. Ive tried ramps, ive tried revving. Just can get it right.:down:

[razo-s.supra]

Anybody have any tips? Id rather not give my expansion tank a blow job but gotta do what we gotta do i guess

[MyE30]

what always works for me is to run the heater full blast with the expansion tank cap off and let the motor run until the fan kicks on and off a couple times, while adding coolant to the expansion tank as required.

also, people also fill the radiator by disconnecting the upper hose and filling it from there.

[razo-s.supra]

what always works for me is to run the heater full blast with the expansion tank cap off and let the motor run until the fan kicks on and off a couple times, while adding coolant to the expansion tank as required.

also, people also fill the radiator by disconnecting the upper hose and filling it from there.

That's exactly what I've done in regards to the hose filling. I do not have a thermo switch for the fan to kick on. Its wired to ignition.

[razo-s.supra]

And thank you by the way! Also are the heater hoses supposed to be pretty hard to squeeze? When running and pressurized?

[e30austin]

Make sure that the recirculation hose (the small one off the top of the radiator) is not clogged anywhere, at the radiator side or the expansion tank side.

[razo-s.supra]

Upon further inspection I saw that my heater core hose (have not distinguished whether it's the inlet or outlet) is pinched in between the firewall and starter. Which is also causing it to pinch at the core nipple (poor circulation). Question is would this cause my over heating problem?

[MyE30]

That's exactly what I've done in regards to the hose filling. I do not have a thermo switch for the fan to kick on. Its wired to ignition.

when the heat in the cabin gets cold is the top radiator hose hot? if it's hot, what you mentioned below could be your problem.

Upon further inspection I saw that my heater core hose (have not distinguished whether it's the inlet or outlet) is pinched in between the firewall and starter. Which is also causing it to pinch at the core nipple (poor circulation). Question is would this cause my over heating problem?

possibly, because fluid is circulated through that metal pipe which connects to the heater core by the water pump. that restriction could potentially be causing the fluid to flow too slowly when the thermostat opens. unpinch that hose and report back.

[razo-s.supra]

possibly, because fluid is circulated through that metal pipe which connects to the heater core by the water pump. that restriction could potentially be causing the fluid to flow too slowly when the thermostat opens. unpinch that hose and report back.[/QUOTE]

This will be my sunday project. Ugh time to remove the manifold

[razo-s.supra]

Also when the heat goes away it is definitely too hot to touch. As well as the spider hose. I will report back once I unpinch it.

[Mwishlist]

When you fill the coolant, fill it from the top radiator hose until it won't take anymore, than fill the rest of the way in the coolant tank. This is the only way I can fill mine and guarantee no air in the system. Hopefully it's just the pinched hose, but if not or if you are draining to fix that; fill it through the top hose.

[razo-s.supra]

Well it is sorted now! For anyone that had the same question. A linked or pinched heater core line will absolutely cause your car to over heat. Live and learn I guess right

[razo-s.supra]

https://photos.app.goo.gl/uQ8Gi1oAuFpNWT9d7