Engine/Transmission (1994 - 1998) Could low RPM kill a turbo???

[Bart]

Ever since I got the truck back from the trans shop (96K) the engine rpms have been down around 500 in gear. A/C would usually kill engine at idle. Could this low r's starve the oil from the turbo and cause it to go out? It only had 115K on it when it went and had very carfull cool downs (400 degrees or less after turbo) since 75K This last weekend I brought the r's back up to 800 in gear and about 750 when the a/c is added. These readings are with the dash tach that I understand is not very accurate.

 

[Smokin Dodge]

400 degrees after the turbo is really about 700 there is a 300 degree difference from before and after the turbo.

 

[Bart]

SMOKIN DODGE. I normally spend 30 seconds to a minute coolin down the turbo (r's at 1,000). If there's a 300 degree difference between the in and out of the turbo what should I cool it down to?

 

[Smokin Dodge]

I cool mine down to 300 and my egt probe is before the turbo, it takes an automatic longer to cool down also.

 

[Deezul1]

Recommended EGT pre turbo for cool down is 300deg. This one of the best reasons for synthetic oil as it doesnt seem to cause the turbos as much trouble when cool downs arnt done properly. It doesn keep you from having to do it but the chance of damage would be less. EGTs after turbo typically read 300 deg less than before turbo and the temps respond slower also.

 

[Bart]

Please explain something to me. If pre turbo temp cool down should be to 300 degrees and there's a 300 degrees difference between in and out of turbo then I'd have to cool my unit down to zero. Is that correct or am I missing something???

 

[illflem]

The big differences between pre and post readings is only while under load running and for a short while during cooldown. Your 300 post is a better indicator than 300 pre, the pre temp is probably lower or equal after a minute of idling.



I doubt if insufficient cooldown caused your problem.

What exactly was wrong with the turbo?

 

[ronco]

Bart, the 300 degree difference in pre and post turbo temps comes from the turbo's ability to absorb heat. Therefore, if your EGT is 1200 pre-turbo, the EGT should be around 900 post-turbo. That is the 300 degree difference mentioned above. As Illflem stated, the 300 post-turbo at cool down is a good number. HTH





Ronco

 

[Bart]

Morning, Illflem! here in the high desert of So. Ca (ambient temps around 100-110 degrees) it takes a loooooong time to get anything below the 400 degrees on Post turbo reading.

As for what happened to the turbo I only know the sitiuation. We went on vacation to you wonderful NW (11' cab over camper) Back down though Utah, and into Nevada and home. Outside of Mesquite Nevada driving at about 65 mph a sudden noise came from the engine bay. It sounded like a belt squeeling on a frozen compressor or Alt. I pulled over and checked and everything was fine at idle. Upon aceleration back on the freeway the noise came back. The noise seemed to follow the speed of the turbo. Slight push of the fuel peddle (over 5 psi boost) brought the noise, vehicle nor engine(tach) had any change yet. Quick gooses on the peddle the noise would come and go. No noise if I kept it under 5 lbs of boost.

"Mistake" I talked to a guy at work who said he rebuilt turbos and superchargers. He had the correct parts. Same as a Case unit. The only problem I saw during the rebuild was that we both forgot which way a metal seal went back in (looked like a silver top hat) (I think we got that right). Next mistake we had troble getting the steel ring on the exhuast end of the vans to go back in. This is where I'm sure the problem came back in. I reinstalled the turbo with new gaskets and drove it to work the next day. Before dawn I couldn't see much out back, but at lunch time I was sure I saw smoke (grey or white) coming from the tail pipe. Before lunch was over there was NO doubt about it. I could have rented it to the Navy as a Smoke Screen layer out in the ocean. That's a joke son! Anyway, I got it back home babing it again. Oil all over the place this time. I contacted a company that works on diesel injection and took the turbo to them. When I removed the turbo this time I saw part of that steel ring in the oil return port of the turbo. That's why I think that we broke that ring trying to reinstall it. The rebuilder had to order a new center shaft with the two vains on it out of Tennesse. Due to the fact that we had been in there and there was more damage they couldn't tell the orginal cause. The first (friend) who rebuilt it said it looks extremely clean inside and didn't understand what was the problem. Anyway, since the professional rebuilt it's working just fine. I just don't want another episode in another 100K.