Cooling system woes

[shawmcbigdis]

You forgot one of the most important things, the gauge cluster. The E30 gauge cluster is extremely common to read too high. This is due to oxidized gauge connectors, loose grounding and failing SI board which controls the gauge.

Until the SI board and cluster are refurbished, you cannot trust a 30 year old failing cluster.

I just replaced the side board batteries and cleaned the ground screws last week. And it was fine before I worked on it. Now all I did was the test drive, then drive it the 100 miles home, and maybe 2 little drives around the neighborhood before I replaced everything, but it was all fine then. Afterwards all hot.

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[shawmcbigdis]

So I just realized something. While the car is running, the upper radiator hose should be pressurized and pretty firm, correct? The hose never gets hard, like its empty, no fluid no pressure.

Am I wrong in that assumption? So does that mean there is such a big bubble in the system the water pump isn't functioning properly? If that's the case I would assume I should empty the whole system and refill from scratch to try and get a better fill. Correct?

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[dnguyen1963]

So I just realized something. While the car is running, the upper radiator hose should be pressurized and pretty firm, correct? The hose never gets hard, like its empty, no fluid no pressure.

Am I wrong in that assumption? So does that mean there is such a big bubble in the system the water pump isn't functioning properly? If that's the case I would assume I should empty the whole system and refill from scratch to try and get a better fill. Correct?

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This is not a good sign. The upper radiator hose should be full of fluid when the t-stat is open. If not, then your t-stat is not functioning properly or your water pump is not pushing any fluid through the system. I would flush all the hoses and the radiator (a clogged radiator could be the source of your trouble here) to make sure that there is no clog anywhere.

[e30davie]

Put the thermostat in a pot of water and chuck it on the stove. Watch it open as the water heats up and watch it close as the water cools down.

Done this yet?

[wilholl]

If the little bleed hose at the top of the radiator is plugged, it will cause all of this nonsense to happen...


from experience!

[shawmcbigdis]

Done this yet?

Not yet, did t have a chance. And now I'm gone for a week.

When I get back I am going to do this. If it is working properly, I will empty the whole system again, flush the rad and refill. I will try finishing it off this time with a op through the overflow hose to try and minimize the air getting in while filling.

Hopefully all that fixes the issue.

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[shawmcbigdis]

So go back from vacation last night. Drained the whole system, pulled the tstat and stuck it in hot water on the stove.

To my shock, it never opened, bad thermostat! Brand new Wahler from Bav Auto. I never would have guessed that would be the issue, but I guess anything can happen.

So off to Autozone, got a new t-stat,some cooling system flush and a bunch of new premix (because I'm lazy). Filled it up with the flush and hose water, ran it for about 20 mins, it did get pretty warm but I didn't bleed it at all, so to be expected. This morning, I drained all that I refilled with 50/50 mix. started it up and bled the system, and it's totally fine. After 40 mins of idling it got up to just barely past the 3rd tik on the gauge. Driving around it just sticks in the middle. Was super easy to bleed. Amazing how much a working thermostat helps.

Thanks for all the help guys, it honestly would have taken me forever to get to the point of checking the tstat because I just wouldn't think something that simple would be DOA.

On to the next project!

[e30davie]

It's always the simplest things.

Now you will never put a thermostat in without first checking it.

[jeffnhiscars]

Always good to see a happy ending. Just an FYI that you want a coolant that is phosphate free.

[shawmcbigdis]

Always good to see a happy ending. Just an FYI that you want a coolant that is phosphate free.

The orange ones like Dexcool have the phosphates right? This is good old green stuff, but I will double check the bottle to make sure.

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[cscracker]

BMW blue is ideal, but the regular green stuff will do. That said, some coolant manufacturers color non-standard stuff green. Just make sure it's normal "conventional antifreeze", ethylene glycol, not dexcool or any specialized type.