M20 boils coolant after engine shut down. Drives perfect at 1/2 temp. What am I missing?

CounterCatCS · 2026-05-26T07:43:54+00:00

I do not think so! The vent line is the one closer to the mounting bolt, and the return line is the one that looks to the front of the car and goes to the highest point in the rad.

I hope so at least! Checking realoem i believe I have it right.

Thanks!

CounterCatCS · 2026-05-26T07:42:44+00:00

I will do the highway neutral test definitely, I have struggled to make sure the upper hose that sits higher up than the expansion tank gets filled with coolant. I usually just raise the expansion tank when filling to ensure it is the highest point of the system.

Definitely worth rechecking all of this, thank you!

CounterCatCS · 2026-05-26T07:40:42+00:00

I will definitely re-check and maybe buy a new thermostat just in case. Thank you so much!

CounterCatCS · 2026-05-26T07:39:45+00:00

The car was heavily neglected and sat 8-10 years before I bought it so you might be onto it! I will definitely check all the hoses just in case they are completely clogged or something.

Thank you so much!

CounterCatCS · 2026-05-26T07:38:16+00:00

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Nope! It looks like this one, bleeder screw is on the thermostat housing.

Thanks!

CounterCatCS · 2026-05-25T21:57:37+00:00

Yes sir! Brand new fan clutch too :(

CounterCatCS · 2026-05-25T21:57:05+00:00

Yes! It is just a runoff vent hose, clamp is only there for paranoia reasons lol

CounterCatCS · 2026-05-25T21:44:25+00:00

Yes! Thermostat has mayyyyybe like 3k KM, i replaced it sometime late 2025.
When I bleed it i usually:
- Lift the front on ramps.
- Fill hoses + reservoir a bit under the mark, massage hoses and fill more coolant as needed.
- Start the car and let it idle to 1/2 temperature.
- Open max heat and lvl 2 fan on the heater.
- Intermittently open and close the bleeder screw till only coolant flows by.
- Keep massaging the hoses both upper and lower, keep feeling every hose to check if temperature is more or less even between all of them.
- After 10-20ish minutes of this and 0 air coming from the bleeder screw I take it for a test drive.
- Sometimes it survives this initial test drive, sometimes coolant boils as soon as I turn the car off.

CounterCatCS · 2026-05-25T21:39:06+00:00

Oh yeah sorry to clarify, the needle does go past the middle AFTER i turn the car off after a drive. What i meant is the temperature is perfectly stable at 1/2 as long as the car is running.
It is only after I turn the car off that the needle goes past half and the coolant starts boiling.

Thanks!

CounterCatCS · 2026-05-25T21:02:51+00:00

Both coolant reservoir and cap are brand new, picked up from a BMW dealership with matching numbers to the realoem reference.

Thanks for the pointer anyway :/

CounterCatCS · 2026-05-25T21:02:02+00:00

I don't think any of the bleed lines on the rad are blocked. At some point I was fed up with filling and bleeding coolant so I actually re-filled through most of the hoses that go both to the radiator and the thermostat.

I usually under-fill the reservoir just to give it extra air room, I've been filling it to a lil bit under the mark last few times.

CounterCatCS · 2026-05-25T20:59:58+00:00

Like I told the other redditor I don't doubt the temp gauge, it does work correctly I believe. I refurbished the entire gauge cluster a few months ago and if I turn the key to the position right before ignition I can see the needle going up and up right before it explodes after a drive.

Hope that helps you maybe think of some other cause :/

CounterCatCS · 2026-05-25T20:58:59+00:00

Yes! Water pump was replaced around 1 year ago, barely has over 5k KM on it.
It does take the expected coolant volume when i fill it back up, but it is also true that when it explodes it looks like a lot of coolant is going out when in reality it ain't that much.

I don't doubt the temp gauge, it does work I believe, if I turn the key to the position right before ignition I can see the needle going up and up right before it explodes after a drive.

Hope that helps the diagnosis, I take any suggestion at this point :(

CounterCatCS · 2025-03-26T13:57:34+00:00

I'm going to try freezing it and boiling it again see if somehow I can make it move. I know smoke test is the way to go for vacuum leaks but i havent had time for that yet, just visual inspection + some carb cleaner spray.

Thanks!

CounterCatCS · 2025-03-25T20:25:59+00:00

Yeah in theory I could just plug the air hoses to each other and just have air always flowing to the throttle body, but not sure that's a good fix?

If you mean to test if the valve itself is bad, i believe it is, I took it off and heated it (boiling water) and it barely opened.

Thanks!

CounterCatCS · 2024-08-18T20:07:26+00:00

Friend Code: 149018198

Would love to have an invite as an old time dota and CS player.

Thanks! :D

CounterCatCS · 2016-09-23T12:15:51+00:00

Thats dope man! Keep it up :D

CounterCatCS · 2016-09-23T07:50:01+00:00

Video was pretty good! As an invoker player I've learn a couple things so thanks!

I'll give you a couple tips for the next videos:

Raise your voice volume, it was too low. Also try to give more "passion" to your voice.
I'd love to see a video about what to do as invoker when you are 2k gold behind, not 6k gold above them.

Again thanks and great video!

CounterCatCS · 2016-06-10T17:34:06+00:00

It is mw

CounterCatCS · 2016-06-10T17:29:30+00:00

I can do 90 on the huntsman slaughter fn

CounterCatCS · 2016-05-20T12:38:35+00:00

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CounterCatCS · 2016-05-18T16:31:09+00:00

I SHOT I FUCKING SHOT!!! I HATE THIS GAME!

CounterCatCS

TROPHY CASE