Engine running hot

[Jeroen]

Please take some time to read this thread and the FAQ section to avoid running in circles! So this is just a recap as we're still at the same point!

Fan clutch: 2 types, old version with 13mm nut up front, new type with 32mm nut behind, old type is extremely sensitive
But in most cases both types of fan clutches are broken even when bought new, because of incorrect storage, that is why the fan clutch was under suspicion from the start and still is.

The issue only shows in traffic so it is 99% sure a air or water flow situation. With water pump and thermostat replaced and the rad relatively fresh and flushed, the fan clutch is still under suspicion. Do you hear it engage more when revving, when the engine is getting hotter?

Just to make sure you can also check ignition timing as it may be a tooth off after the timing belt change.

[yatisr]

I had the fan clutch checked, the radiator serviced and the thermostat bored out but the running hot problem persisted.

I then read the thread on Performance Distributors and noted that the 323I used different distributors depending on the year of manufacture. At the start of this thread I said that I had changed the distributor on my car with one purchased new from BMW. The number on this new distributor was 0237 302 032, which according to the thread on Performance Distributors fits the late model E21 323I. My car is a 1982 323I. She was built in April 1982. So in theory this new distributor should have been a perfect fit for her.

The old distributor on the car has the number 0237 302 040, which according to the thread on Performance Distributors fits the 1983-84 323I. I presume from this that this distributor must be for the early version of the E30 323I.

In any event, I had the old distributor reinstalled together with a new functioning thermostat (the old one had been bored out as part of the troubleshooting exercise), and the running hot problem disappeared! Can anyone explain this? The new distributor from BMW worked fine except that the car ran hot (she did not overheat). Outwardly, the only difference with the old distributor on the car is the vacuum. I can't say if the distributors are different internally.

The E21 in Malaysia in the 1970s and 1980s- if memory serves me right- had a reputation for running hot. Could the 1983-1984 distributor on my car been BMW Malaysia's answer to curing this problem as uprating the cooling system's capacity to cope with the generation of more heat was not a viable option?
Yatis

[Jeroen]

The difference between these distributors probably are different timing advance/retard setups indeed, so perhaps a slightly different timing (normally that would be off then) might cause the engine to run less hot. But you had the thermostat changed (again) as well then?

[yatisr]

The thermostat was changed twice as part of the troubleshooting process. I first changed it with one I purchased from BMW Germany. It made no difference. Then my mechanic suggested boring through the thermostat. I was skeptical but allowed him to do this as I didn't have any better ideas at the time. Although this had the effect of slowing down the initial temperature rise, the car still ran hot when she had to negotiate slow traffic. I then hit on the idea that the new distributor might be the problem and reinstalled the old distributor together with a 70 degree thermostat, which is perhaps more sensible in Malaysia than the 80 degree thermostat supplied by BMW Germany.

In the end I have ended up with my old distributor refitted in the car. The moral of this story is : "If it ain't broke don't fix it".

[Jeroen]

well a lower temp spec thermostat is a good choice over there, actually I'd expect these to be fitted as standard over there!

there have been issues with new thermostats before (not opening fully) including OEM and as your temp issues mainly occur in traffic I wouldn't be surprised the thermostat was the culprit, restricting flow.