Piston condition and misc questions

[sc2_ct]

Well, I just picked up a 91 Talon TSI AWD today, and started tearing into it right away. I always do a full tune up and check up on a new car (oil, gear lube, tranny fluid, coolant, belts, hoses, plugs, wires etc...). Anyway, on looking this car over I have a few questions as to what is the norm for these cars.

When I took out the #2 spark plug I noticed a little bit of engine oil on the threads and the spark plug seat, so I'll be doing the valve cover and spark tube seals this weekend. While I had the old plugs out, I checked out the pistons visually just to see what kind of condition they were in and noticed that the pistons had a bit of carbon buildup on them. I know that carbon buildup is normal, but I was wondering how extensive it should be on the DSMs. I figure that since it's modified a bit (bigger turbo and higher boost), that there is probably some additional enrichment taking place.

The compression is within 5% across all four cylinders, and there was virtually no change in compression when I put a few drops of oil in, so the rings appear to be in good shape. What should the compression numbers be? Also, what would be the leakdown test service limits? I picked up a Haynes manual, but can't seem to find this info in there and haven't had a chance to hunt down a FSM yet.

As far as the gear lube goes, I wasn't planning on attacking that until Sunday, and of course with it being Easter, I don't think many stores will be open. Does anyone know the gear oil capacity for the transfer case? I'd like to make sure I have enough. Also, has anyone experienced any problems when using synthetic gear lubes (Mobile 1 in particular)?

As for spark plugs, what do people think of the Bosch platinum plugs on this engine (just single strap)? I know on some cars they tend to be much more prone to fouling. The NGK-R's that were in there looked pretty good, but were a bit worn. I just bought the platinums out of habit, but then considered whether I might not have been better off with a non-platinum plug with this being a turbo engine and all.

Also, the coolant temperature gauge is not responding, but the ECT sensor is behaving as any other thermistor I've seen does according to my DMM. Is it likely that it is the gauge itself that is faulty? It doesn't really matter since I'll just be putting in an autometer coolant temperature gauge anyway, but it would be nice if the gauge didn't just hang out there by zero

Thanks for taking the time to read this long-ass post, and thanks in advance for any information you can provide.

 

[92awddsm]

The transfer case uses less than 1 qt. Stay away from the bosch plugs. What size turbo is on the car now? If small and stock boost levels, ngk bpr6es is the plug to use. If higher than stock boost levels, bpr7es. Gap either at .030 and you will be fine. As for the gauge, the temp sending unit might be bad. Coolant temp sensor and temp seding unit are two differant things. Im not sure on the 90 but my 92 has a 1 wire plug at the thermosta housing that works the gauge. The 2 wire plug next to it is for the ecu. Check to make sure the single wire is hooked up and not cracked or broken. Next you need to take the car to the dealership and have the transfer case recall work done. Hope this helps.

 

[sc2_ct]

Originally posted by 92awddsm
The transfer case uses less than 1 qt. Stay away from the bosch plugs. What size turbo is on the car now? If small and stock boost levels, ngk bpr6es is the plug to use. If higher than stock boost levels, bpr7es. Gap either at .030 and you will be fine. As for the gauge, the temp sending unit might be bad. Coolant temp sensor and temp seding unit are two differant things. Im not sure on the 90 but my 92 has a 1 wire plug at the thermosta housing that works the gauge. The 2 wire plug next to it is for the ecu. Check to make sure the single wire is hooked up and not cracked or broken. Next you need to take the car to the dealership and have the transfer case recall work done. Hope this helps.

The turbo on the car is a Garrett T3 60 trim (I can't see clear enough to identify whether it is a regular 60 or a Super-60 though, but that's just a few % according to my compressor charts). I haven't gotten a chance to really open it up (I won't have it registered and on the road until Monday), so I can't tell the precise boost pressure but would assume in the ~15psi range. I pulled the plugs and they did appear to be the 6's, so I'll definately pick some colder NGK's when I go to AutoZone tomorrow.

As for the temperature sender, I'll have to look for that in the manual, and if all else fails and I can't find the info here, I'll call the dealership too find it.

Thanks for the info on the transfer case capacity, it appears I've got enoough lube for 16 changes then (I've got a case of the stuff since it's just so damn useful .

EDIT: What's this transfer case recall work you mentioned?

 

[92awddsm]

Transfer case failure due to leaking seal and/or driveshaft yoke. A real safety hazzard and the recall is never ending, even if recall work has been done before. I havent had it happen but others on the tuner can tell you, its no fun having you transfer case lock up at 70 mph. Especially when it is due to design flaws.

 

[sc2_ct]

Wow, that is pretty serious, I'll take it down as soon as it's registered and driving. Thanks much for the heads-up!