Time for a top end job?
 

My '87 911 with 98000 miles has used a qt of oil every 1000 + miles until recently. Now that consumption has doubled or tripled in the last few months. I had the valves adjusted in Sept 2011 at 91000 mi and also had a leak down check. All cylinders were 98-99/100 with one being 97/100. Before my last oil change I was getting almost 1500 mi a qt. since that oil change my interval has dropped to 800, 400, and now 300 miles to a qt. since last May. My engine has never leaked oil, starts easily and runs strong. It does smoke a little at start up but I see no smoke while driving. Is it normal for the oil consumption to increase that suddenly? I would have expected to see a slower degradation. I don't drive the car as much as I used to. Maybe once or twice a week and most of the driving is a 10-15 minute trip to work and back. Last weekend I did drive to the other side of Houston and it ran fine. However even in the 50-60 deg weather my oil temp never rose above 180 deg during the 45 minute freeway speed drive. So my question is am I looking at a top end OH or could something else be the problem? Would a thermostat problem contribute to this increased oil consumption?

Any suggestions for a more definitive diagnosis? What should I budget for a good top end job? Any ideas on what a recent engine rebuild would add to the car's value versus just selling as is and looking for a newer model 911?

100k on a 3.2, needs guides. The bottom end will be excellent but the weak area on the aircooled is always the heads.
While youre there, install the bottom row of studs in steel, new chain rails, and I always like to open the bottom and reseal center case with new intermediate shaft bearings, sealant on center line and replace cross bolt o rings while cleaning the case in and out. You can also tell if anyone has ever been inside before.
Bruce

I think I'd rather have a pcar that I know well then a newer one I don't. Chances are you could get something newer that ends up costing you more to get up to snuff then yours. The top end rebuild would be good for value as long as it's done right by a reputable shop, but it may not be needed just yet cuz something sounds fishy to me. If it started with your last oil change then I'd suspect that's where something went wrong. Did you change oils brands or viscosity? What about the filter, Mahle? Same filter as usual or different? Did you do the oil change yourself or did somebody else do it?

I did the oil change myself using parts from Pelican. New crush washers and Mahle filter. I use Mobil 1 15W-50 as I have since I got the car from the PO. That is what they let the Porsche dealer for all their services. my only other funny issue is the lack of oil temp. Throughout this past fall and winter months here in Houston my car never gets much above the 180 mark if at all. Even on that 45 minute freeway drive last sunday the temps never went above the 180 mark. Could I have a leak that only exists under operating pressure and doesn't leave a puddle on the garage floor?

Any suggestion on how to try and diagnose this problem? A co worker suggested adding a UV dye to the oil to track leaks. I have never heard of that except in A/C service.

Mine runs at that temp too, so I don't think that's a problem. Your temps are good so it sounds like both your thermos are working. However, every motor is different...where did your temp run normally before your last oil change?

Also, if there's a pressure leak you should be able see it happen while in the garage and/or see evidence of it. Your oil pump is run by a chain on IS from the crank, so when you turn up the RPMs you're turning up the pressure too. Make sure you warm it up first. Gotta love a good motor mystery:)

Last summer it ran just below the 210 mark on the temp gauge. Before I added the tail last Feb. it ran right at the 210 mark. It would only go above the 210 line if I was stuck in stop and go traffic. Then it would get near the 240 line.

Okay, so did the lower temps you're experiencing start just after last oil change or when you changed your tail?

After I added the tail my temps dropped 10-15 deg. These 180 deg temps have only occurred since last Oct.

That seems to correlate with the valve adjustment. When did you change oil last and were the temps lower before the oil change or after?

Also, I assume you have a front cooler. Do you drain it of all the old oil and drain the lines running up and back to and from it when you change oil? How many quarts do you start off with to fill it?

Oil was changed last May. I just get it warm by running around the block and then drain the tank and the crankcase. I don't do anything else to drain the oil lines or front cooler. I usually fill with 8-9 are and then go get it real hot and then check tue level and top it off. I drain the crankcsse first and then the tank if that makes any difference.

Sounds all good, so I think we can rule out your oil change;)

Assuming your oil temp readings are good then it sounds like your external thermo is currently doing it's job, but that may not have been the case back when you were running hotter. Therefore, we have narrowed your oil leak down to the front oil cooler/oil lines. I suspect you'll find one of the lines (prolly pressure line to the front cooler) has developed a hole in it that only leaks when you're out running it good up and down the road. You'll prolly have to pull both the lines running up front from the thermo and be carefull with thermo fittings cuz they are easily buggered up...It's a dirty job, but better then a top end OH:p