Heat problems 1991 318is E30

[Indy125]

Hello All!

I noticed that I didn't have heat while sitting at a light the other day. I went right to the radiator to make sure the fluid level was proper and it was low, not empty, so I added to the fill level. However, that didn't help the heat issue. After a little bit on the highway, the heat came back. Car doesn't over heat.

Maybe there is an air bubble trapped in the heating core or somewhere else? I was also thinking it was a water pump issue? So in the driveway today, I revved the engine and took notice that the temp gauge goes down as its revved (cooler), and didn't necessarily get the heat back. I thought that the temp gauge getting cooler was strange. Maybe thermostat? Any thoughts, or suggestions to point me in the right direction? Tomorrow I will remove the cap and rev, and maybe a bubble will come out.

Thanks everyone!!


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[dworthy]

Hi Indy125.

If the car is fully warmed up and the needle does drop, it can point to a bad thermostat getting stuck open. On your car there is no buffer on that needle so when it's hot, you know it, just like being cold, the gauge will move around a bit. Just remember that as long as it stay between the two marks, it is normal.

I think you need to bleed the system out, for not heat is not good in the winter, this way you can rule that out first. If it bleeds properly and your temp needle stays by the lower tick mark after the blue area, then I would say to start with the thermostat.