Coolant Warning and Temperature Guage High

[angusbn]

Cool morning these days yet after maybe 10 minutes, the coolant warning displays and the temperature guage is in the red zone.

Literally, if I pound on the dash above the instrument cluster the damn needle lowers back to the 12 o'clock position in like 10 seconds.

New BMW coolant, t-stat, water pump, hoses, etc. a couple of months ago.

WTF?

[uscharalph]

Did you bleed the cooling system of air bubbles?

[Mordan]

Cool morning these days yet after maybe 10 minutes, the coolant warning displays and the temperature guage is in the red zone.

Literally, if I pound on the dash above the instrument cluster the damn needle lowers back to the 12 o'clock position in like 10 seconds.

New BMW coolant, t-stat, water pump, hoses, etc. a couple of months ago.

WTF?

it is funny because I have the same kind of issue on my M20.

The temp needle is at 12h then after a roundabout, it goes to the red!! and it stays there. I freak out and stopped the engine.

sometimes it also goes from very hot back to 12h quickly.

new pump, new head gasket, new coolant.

usually when going at low speeds, temp needle goes near red, even though my mechanical fan clutch is very tight.

i removed my t-stat and now temp needle is just above blue, except for low speeds periods where it goes up to first white stripe.

and I bled the air bubbles,

[Kibokojoe]

Read somewhere that you can drill a hole in the thermostat and release the air trapped in this area.

it is funny because I have the same kind of issue on my M20.

The temp needle is at 12h then after a roundabout, it goes to the red!! and it stays there. I freak out and stopped the engine.

sometimes it also goes from very hot back to 12h quickly.

new pump, new head gasket, new coolant.

usually when going at low speeds, temp needle goes near red, even though my mechanical fan clutch is very tight.

i removed my t-stat and now temp needle is just above blue, except for low speeds periods where it goes up to first white stripe.

and I bled the air bubbles,

[E34-520iSE]

Yeah you can drill a small hole in the T-stat, it really does help. M20's are a pig to bleed, and the temp-guage swingometer symptom is proof lol! If you 'blow' the air pocket out of the heater matrix by loosening the t-stat & rad bleeders and erm, 'blowing' the coolant down through the system you will get the coolant coming out of the t-stat bleeder then the rad bleeder shortly after. Remember to close each bleeder when coolant appears, and also to top up the expansion tank as the level drops. This method has worked for me many times on many makes of car but you must be careful!!!

HTH,

Shaun M

[Rus]

The temperature gauge is operated by the sensor under the hood, which changes resistance placed between the signal wire and the ground reference wire. Since pounding the dashboard fixes the issue, you probably have an insulation problem with the signal wire. If it touches a metal piece somewhere along the way and is not insulated, it'll peg the gauge in the full hot position and set off the warning. Find the place where it is grounding, and you'll solve your issue. Good luck!

[Rick L]

Always wondered about the arrows on the thermostat. Found out the arrows mean UP or DOWN. You need to point the arrow either at very top or bottom. At least that's the correct way of putting in a thermostat. DON'T LET SOMEONE TELL YOU IT DOESN'T MATTER WHICH DIRECTION IT POINTS. Anyway, you should just take you car to a shop with pressure coolant flush system to get that stubborn air out. I had an issue with my car overheating and I tried everything but problem remained. Local shop had the pressure system and now it is perfect (heats up fast and stays perfectly at 12).

[632 Regal]

arrow or checkball thingy goes UP

Always wondered about the arrows on the thermostat. Found out the arrows mean UP or DOWN. You need to point the arrow either at very top or bottom. At least that's the correct way of putting in a thermostat. DON'T LET SOMEONE TELL YOU IT DOESN'T MATTER WHICH DIRECTION IT POINTS. Anyway, you should just take you car to a shop with pressure coolant flush system to get that stubborn air out. I had an issue with my car overheating and I tried everything but problem remained. Local shop had the pressure system and now it is perfect (heats up fast and stays perfectly at 12).

[Rick L]

I was told either way will work as long as it is at the top or the bottom. Some of the thermostats have two arrows (opposite end of each other).

arrow or checkball thingy goes UP