Low coolant E36 328is
 

Recently the car appeared to start losing coolant. Every 100km or so the coolant level would drop low enough that it would trigger the coolant sensor, causing the low coolant level message to pop up.

Parts replaced
t-stat
t-stat housing
radiator cap

The headgasket appears to be fine. There's no coolant in the oil and there no oil in the coolant.

I also did a pressure check test and it held at 1.4 BAR for 2 hours.

I'm at a loss on what else to check for.


Thanks
Ivan

You can go to Lordco and get a small jar of ACDelco Tracer Dye.

With a yellow lens you can see where and if the coolant is leaking.

surprised expansion tank wasn't mentioned

Do you ever smell coolant when you pop open the hood?

There's a chance your water pump is on the way out and it's leaking through the bearing.

Thanks I thought I may have smelt something need to take the car out and try again.

Pay attention as you are driving or when you park your car. Pop open the hood and look for signs of coolant leaks at the rad fan/water pump area. It will be most obvious when you smell coolant.

This happened to me - I had a phantom coolant leak, very much like the symptoms you described. I had it pressure tested and it came back good.

Then one day, driving down Kingsway in heavy rush hour traffic, I notice smoke coming out of my engine bay and the coolant temp spike. Had to pull over to find out the water pump's bearings had failed and that was the root cause of my cooling system issues.

I don't want to scare you, and pray that it isn't the same issue you're experiencing because it was an expensive repair (I had to replace the entire system for safe measure.) I would stop changing parts until you can confirm the root cause. Good luck!

With the age of these cars, you want to use the "shotgun" approach to cooling system repairs (esp. since the cooling system is a weakpoint).

I recommend this since once you need to replace one or two things, other items will fail shortly thereafter.

For example, on my e30, for YEARS I had a slight overheating issue. Guage would go all the way up to 3/4 yet the thermostat was new, no leaks, no oil in coolant or vise versa, and no drop in level. Then one day a new mechanic suggested I desperately needed a rad since the lower section of my current one was actually drooping downwards. He said it was probably the original one from 1988. After that replacement my cars temp NEVER hit's 12:00 anymore, just a hair below (where it should be).