If the ECU is bad, I may have one. What's the number? BMW number from 3/87
is 12141730793. Off-hand, I don't know the Bosch number. Check here:
www.realoem.com under the archive section for e28.

Bill in Omaha
'86 535i

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I moved to Omaha after Katrina. I'm from Biloxi, MS! If you like, I can send
the CD I've built that covers a lot of troubleshooting for the e30, e28, and
a few others. I even have the Haynes in pdf. The ECU may be reading a
gap/bubble in the coolant system, if the gauge fluctuates. I checked mine
with the engine running and the reservoir open (cap off). I also squeezed
the hoses until it warmed up good and thermostat opened. I added until it
near overflowed and capped it. Be careful on revving the engine when warm,
it will overflow with the cap off. This technique has been flawless for me
since 1988. I also have a few relays I can send. I get them from the parts
yards and test them on the meter. I got them parts! Let me know what's up.
The CD is free. It could also be fuel injectors. I have a set of those too,
good and inexpensive.

Bill in Omaha
'86 535i

My sad tale thus far:

I have the Haynes, easier to find, though I might look for all the
manuals I can get! I had already bought a coolant temp sensor, which
turned out to be a good thing, because the old one crumbled when I
removed it. It didn't help though. I unplugged the temp switch so the
gauge read 0 (they didn't have the part in stock) No difference.

I did replace it with a good quality one. We have a parts store in
town that specializes in european import car parts. I don't mind
paying a little more even if I just "think" I'm getting a better part.
I'm a sucker like that. No, actually they are a good bunch and they
carry the real stuff. Bosch etc. Thermostat also didn't help.

I want to try this one. Haven't yet
I was just going to replace it. Seems like there are three different
possibilities. I'm going to try to locate it and get some numbers to
match it up.

Oh I will!

Bill, thanks for your input...I'm Mike in Mobile AL

It's really strange. All the obvious things haven't helped. The gauge
climbs and it starts stumbling.When it happens it's revving up and
down and the temp needle does likewise. I was wondering if there might
be a grounding problem...or a computer problem?  It's hard to tell
what's happening first. There's no particular reason that it should
overheat...and so quickly...especially since I replaced the
thermostat. It's full of coolant, the water pump's spinning, fan
clutch seems to be pulling air through the radiator, the color of the
coolant looks good, it runs great until the stumbling starts, so I
don't think its a cracked head or head gasket. Then, just as soon as
it starts...it's fine again. But I don't trust it right now. I zip
through the neighborhood...but I don't want to take it out on the open
road! As long as the temp needle is in the middle, it runs fine. If it
goes above 3/4 then it starts doing its thing.

TIA
Mike

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1. Get the Bentley manual and test the coolent-related senders/sensors.
2. Change the thermostat if it's over 2 years old.
3. Check the fuel pump relay. it may be affected when it gets hot under the
hood.
4. Get back to the group with your findings.

Bill in Omaha
'86 535i

Alright all ye who are strong in BMW-fu

98.4 percent of the time this car runs absolutely fantastic. The other
times it acts as though it is overheating then stumbles and runs quite
poorly. The temp needle climbs, it stumbles, won't accelerate, then a
few minutes later it clears up and again...runs great. I have replaced
the thermostat. I have, but have not yet replaced, the coolant temp
sensor. I have replaced the airflow meter, on the advice of a
mechanic. Fortunately, it was cheap...(EBAY) but it made no
difference. I love the car...It's in great shape...but HELP!