Noob - Temperature-related issue??

[bbiess]

I purchased an '87 325is a few weeks ago (my first BMW) and have been enjoying it immensely. I drove it a little over 600 miles to get it home and it ran flawlessly.

I had a bit of a weird sequence of events this morning that I wanted to see if anyone has some insight into.

I started the car, let it warm-up for a couple of minutes (it was probably in the low 50s this morning) and pulled-out heading to my local Starbucks for a cup-o-joe. About 5 minutes into my drive I noticed my coolant warning light go on, which didn't alarm me too much as I thought I'd just check the coolant level when I got back home, but then I experienced a couple of chugs while doing ~25mph where it felt like the engine was bogging a bit. Freaking a little I pulled over, pushed-in the clutch and gave it a couple of revs and it seemed fine. Got back on the road, noticed the same thing one more time (not as bad this time), however, the engine seemed to recover this time so I kept going still at around 25mph.

Not long after that I noticed my engine temp was increasing (again at a low speed), but would cool-down at say 35mph. The engine coincidentally was running smoothly with no loss of power whatsoever.

I wasn't feeling too comfortable at that point so I bailed on the coffee idea and headed home.

I checked the coolant-level and it is indeed a little low - not quite at the minimum level, but definitely looking like it could use to be topped-off.

I did a little research in the forums and am suspecting a thermostat and/or a fan clutch - or for that matter just adding coolant (I'll try that later today), but that doesn't explain the chugging. Does anyone have any thoughts on what that was about? Was it related?

The engine (a Pete McHenry-built masterpiece BTW) has a new timing belt and water pump and head gasket (new = 5 years old) and was inspected last week by a local shop, so while not outside the realm of possibility I wouldn't suspect those components to be the issue. I don't know whether the fan clutch was replaced during the build though.

One other thing, and I have no idea if it could be related, but I thought I'd mention it anyway, it's been raining like crazy here the passed few days and while the car was covered with a waterproof car cover it's certainly been exposed to a LOT of humidity. Again, no idea if that factors-in, but thought it was worth mentioning.

So my questions - what should I check and in what order? Any thoughts on the chugging episode?

Any thoughts, ideas or suggestions are appreciated. Thanks!

[Sagaris]

The low coolant light on the check panel is usually a fluke and due to a dirty/broken sensor if the coolant level is fine but the light illuminates. You can make an attempt to clean it (I have been successful 1 out of 2 tries without breaking it) by removing the coolant level sensor from the overflow tank and CAREFULLY bending the plastic prongs at the bottom which will allow you to remove the white cylindrical float. There is typically crud inside that you can wipe out. If you are successful with that then GREAT! but don't be sad if you end up breaking the prongs at the bottom of the sensor and need a new sensor. They are ~$25 new.

The temperature rising could be one of three things

1) sounds like the fan clutch is weak. you can do a "newspaper test" fold up a few pages of newspaper and see if the fan cuts it or stops (google e30 fan newspaper test for more info)

2) there could be air in the cooling system for which it needs to be bled (turn the heater temp control knob to full HOT (blower can stay off), park the car pointed uphill on an incline or on ramps to get the front of the engine higher than the rear. run the car at 1500-2000 rpm as you crack the bleeder screw on the thermostat housing until there is a solid stream of coolant flowing out without interruptions (also see the bentley manual for more info)

3) the temp gauge could be "dancing" due to a bad connection on the back of the cluster. Try tapping on the temp gauge when the temp goes past 1/2 and see if it bounces back to a reasonable temperature, if so, it is gauge related.


The poor performance could be due to a number of things, bad ignition wires, coolant temp sensor, crank position sensor, DME relay, oxygen sensor, vac. leak, I wish I could be more specific with this problem but its the kind of thing that you either throw parts at, or get someone very experienced to drive it, listen to it, and check it out. Nezt time it 'chugs' keep an eye on the tach and the MPG econometer and see if either of them drop to 0 while it happens.

A tach going to 0 indicates a DME relay, crank position sensor, or some other DME related fault. An econometer going to 0 indicates a bad C191 fuel injector harness under the intake manifold.



Best of luck, let us know what you find!

[bbiess]

Sagaris - Thanks for the suggestions! I'll definitely run-through the list you provided to see if it resolves my temp issue.

Interestingly, the gauge anomalies you mention are evident in the car and in fact I noticed both on my looooooong trip home, but chaulked-it-up to the fact that the tach and econometer are both 24 years old and were just old. While I thought it was odd, I didn't notice any performance impact when it occurred, but I'll definitely be paying attention now if/when my performance problem arises again to see if the gauges act in the manner you describe.

I really appreciate the info and will post my progress. Thanks!