Engine Cooling problem
1986 BMW 325 6 cyl Two Wheel Drive Manual 225000 miles
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Hi, I had the question about my temp gauge running in the red. It starts off normally, but as time progresses, it now climbs to the last notch, engine still not overheating though?! I pulled the instrument panel out and checked the mounting nuts on the backs of the fuel and temp gauge and they were both tight and seemed to be making good contact. Also there are many sensors and switches on the thermostat housing...what are they? Thank you in advance.

Inspect and test the engine coolant temperature switch and the coolant temperature sensor-See below

Send the vehicle identification number so I know how to answer the question.

Hello again, my vin is WBAAB5406G9633689. I was wondering which one sends the info to the gauge when the vehicle is running because even with the gauge pegged out, when I stop the engine then turn the key on, the temp gauge reads right at or below the midway point. Thanks again.

The image above shows the T-stat housing exploded view. There are four temperature measuring units in the housing. The physically largest one is the thermal-time switch and it regulates the cold start. The other three are temp senders, the two that have clip on connectors and the one that has but a single terminal. The single connector is for the "idiot" light at the far right side of the temp gauge. that leaves the other two. One of them is for the engine management and the other is the sender for the temp gauge. As you tell the story the thing that comes to mind here is the instrument cluster conversation in an earlier thread is what might be the problem, when you had it apart did you inspect the service interval board? The information from the temp sender goes through that board, if it's bad it needs to be replaced.

Yes I checked the service board while it was out but obviously there could be issues with it which I am unaware of. I appreciate your help and a donation will be in order for all the information I've gotten from the forum as soon payday rolls around. I'll check the sensors and stuff out then hopefully I won't have to buy a whole service board. Thanks again.
Jeremy

There are several aftermarket suppliers for that board. Realoem.com wants $244 bucks plus core. Looks like it could be price matched elsewhere, I'll research it, $244 is a bit much in my mind.

I usually try to go through bavauto.com or germanimportedparts.com; they seems to have the best rates including shipping over a certain amount, although when I look it up through both of them, it shows a different board than the one in mine. The label on my car says it was manufactured in 9/85 but that type of board looks tiny; the one in mine matches the ones from 1/86 on, should I match one up that looks alike or the one they say is for my car? Thanks.

Look for P/N 62-11-0-152-533