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View Full Version : spooky rpm surge and coolant light...


94Touring
10-26-2009, 08:25 PM
Hey guys,

I am experiencing an issue that is REALLY similar to a head gasket issue on my old acura, but without the fluctuating temperature guage and overheating....

Here's what's up... Occasionally while driving the RPM's will dance up and down about 300-500rpm. doesn't matter what gear the car is in or what speed. Directly following this when shutting the car off the "COOLANT LEVEL" message displays on the DIC. Everytime I let the car sit for a while and then check the coolant level and the level is always about 2-3 inches above the COLD mark on the tank. Spooky right!? The temp guage never moves from just below half way between hot and cold...which leads me to think it isn't a headgasket issue (not to mention no apparent loss of coolant).

What do you guys think it is? T-stat? Water pump? Cruddy coolant? Bad sensor?

I'm taking it in on Friday if I can't get any answers before then...I don't want it to strand the missus...

Thanks guys!

Tourburgring
10-26-2009, 09:22 PM
Sounds like two seperate issues to me. The fluctuating engine speed could be a vacuum leak or possibly an ECU problem. The false Low Coolant Level is probably a bad sensor - a common problem.

94Touring
10-26-2009, 09:29 PM
Would a bad sensor cause the ECU problem? What would the code(s) be?

woodnthings8
10-27-2009, 03:24 PM
Coolant sensor is what needs replaced. They run about $20-30 online and take about 30 minutes to change for the first time, you will need to drain some coolant so buy some if you dont have any.

The surge issue could be a few things. You say rpms fluctuate 300-500, does the car accelerate or decelerate during this? If the car is not changeing speed and rpms climb, you have a transmission issue. Have you checked the fluid level or serviced it in the last 30k? You could be experiencing the torque converter unlocking and locking which is usually about that rpm range. If you drive in S3 do you notice the problem?

solli
10-27-2009, 03:33 PM
False indicator is prolly the coolant sensor. Once replaced they're warrantied for a year but mine went again within the year...

rdc
10-27-2009, 06:29 PM
Coolant sensor is what needs replaced. They run about $20-30 online and take about 30 minutes to change for the first time, you will need to drain some coolant so buy some if you dont have any.

The surge issue could be a few things. You say rpms fluctuate 300-500, does the car accelerate or decelerate during this? If the car is not changeing speed and rpms climb, you have a transmission issue. Have you checked the fluid level or serviced it in the last 30k? You could be experiencing the torque converter unlocking and locking which is usually about that rpm range. If you drive in S3 do you notice the problem?

Surging could be "pendulum swing". As stated, trany hunts between 3 and 4th gear around 2500-3000 rpm going up a slight grade. Usually indicates a trany problem. I have heard mostly seals. Even so, it may need a rebuild or replacement. Do a search. BTW, these tranys need to be serviced about every 30,000 miles.

Mine is doing it a little and I am worried. My indy says a quality full rebuild is about $3,000 installed.

94Touring
10-28-2009, 07:06 AM
i bet it is pendulum swing, now that i think about it... Anything i can do from a service standpoint? any additives or anything like that? This car only has to last me two years, so hopefully it hangs on!

Thanks guys!

woodnthings8
10-28-2009, 12:09 PM
I just had a trans rebuilt & new converter for $1400 out the door. Shop around though, I had prices anywhere from 900-4500. I did the removal and the install myself with my 17 year old son who has never worked on a car. I do have a large shop but only used basic support tools and it went pretty easy. Took longer to get the belhousing bolts loose than anything else. Trans was at the shop for 3-4 days.

rdc
10-28-2009, 12:24 PM
I just had a trans rebuilt & new converter for $1400 out the door. Shop around though, I had prices anywhere from 900-4500. I did the removal and the install myself with my 17 year old son who has never worked on a car. I do have a large shop but only used basic support tools and it went pretty easy. Took longer to get the belhousing bolts loose than anything else. Trans was at the shop for 3-4 days.
That's a great price? Any warrenty etc on the trany? Local rebuilder?
The problem in my area is that no local trany rebuilder seems to have a handle on rebuilding any BMW tranys. Most BMW indy shops in my area use high quality nationwide rebuilders which cost more plus shipping. don't even think dealer!

woodnthings8
10-28-2009, 04:36 PM
It was a 12k-12mo warranty. Any decent transmission shop should be able to do it. It is a GM transmission after all. I had several shops looking for a "stimulus package" from me, trying to tell me that BMW's were special. I argued with a few of them and told them it was the same transmission as the Isuzu Troopers, Honda Passports, Acura's, and Cadillac uses. The shop I took it to was a "local" one that is run by the mechanic and his wife. I talked to him a bit about the transmission and how "special" it is. He just laughed and said they were pretty common and he could tell me what was wrong and probably give a price within a $100 from my description of what was going on. I pulled a parts breakdown online and checked it out with the prices everyone was quoting. Most were trying to rip off the consumer! I did find a few places online that would offer a similar warranty and had prices around $1200-1500 plus shipping.