Perplexing Problem - 84 930

AFJuvat · 05-23-2005, 07:37 PM

Hey All,

I have a bit of a puzzler for you. I've been knocking my head about trying to find a solution and haven't gotten one yet. Therefore, I'm throwing this one out to the community to see if anyone has seen anything like this before.

1984 930, Aftermarket wastegate, B&B exhaust, K-28 Turbo, Garretson longneck intercooler

Vehicle presents itself as a well maintained 930 with some custom additions. Customer had us install (against professional advise) a K-28. Customers complaint is severe engine smoke once engine reaches operating temperature.

Customer has made several attempts to control\moderate\shield the heat generated by the K-28 to include air ducting, fiberglass insulation etc.

Customer brings vehicle in, we confirm the problem, intercooler is too hot to touch. Bumper is removed, stainless steel muffler is charred. Copper exhaust gasket between turbo and muffler is partially melted.

Obviously, the k-28 is running entirely too hot. Customer requests install of K-27. K-27 is installed, further examination of the muffler shows the baffles are partially melted and deformed. Cut open muffler and gut it - muffler got hot enough to melt the fiberglass insulation.

Engine leaks down perfectly (less than 1% leakage) and passes a compression test (do not recall compression numbers) Oil feed for turbo and scavenge pump for turbo is operating correctly. Valves adjusted

Install new K-27, install muffler, test drive car, after car reaches operating temp, car starts smoking.

Valve covers removed again, exhaust valves are partially compressed then wiggled to see if valve guides are excessively worn - none found. As a double check, cylinders set to TDC, charged with 90 PSI of air, valve spring compressed, keepers removed, springs removed and valves checked again - no excessive play found.
Borescope indicates no burned valves

Considered unlikely, but consider possibility of defective turbo. Install yet another new k-27. Problem repeats - engine smoking heavily once engine reaches operating temp.

Smoking details:

After each run, oil is found on the COLD side of the turbo, as well as the pop off valve. and the "down" pipe from the airbox to the turbocharger. Intercooler has contained up to 4oz of oil. Crankcase breather has some oil in it, but not what would be considered excessive. Vent line for oil\air seperator is not connected to air intake - has seperate filter not connected to intake stream

Turbocharger has aftermarket oil sump (GHL) - not connected to intake stream.

Oil pressure is normal throughout temperature range

At this point, I am convinced that there is something wrong with the motor. Unfortunately, all tests show that there isn't anything that you can point a finger at. I am thinking that the heads got so heat soaked from the K-28 that the valve guide is actually moving with the valve once the engine gets up to temp.

Any ideas, or anything you think I may have missed is appreciated. As I said, I'm convinced that it is a problem with the motor, but I want to hear other ideas from "disinterested 3rd parties" before I tell my customer that I have to tear into his motor.

Thanks

AFJuvat

mmastro · 05-23-2005, 07:42 PM

just curious, what's your CO%? Too lean and you heat up the turbo and burn everything in it's path.

Randy Blaylock · 05-23-2005, 07:44 PM

Confirm the timing/vacuum advance/boost retard.

AFJuvat · 05-23-2005, 08:03 PM

Thanks for the input.

CO% is at 2% - non catalyst.

Did not check the timing - the engine runs fine throughout the operating range. Will double check that tomorrow.

AFJuvat

afterburn 549 · 05-23-2005, 08:04 PM

Are you sure the turbo is able to drain properly.....the pump pumping?? no kinks and stuff??Return line swollen shut??

AFJuvat · 05-23-2005, 08:08 PM

Confirmed that oil is indeed pumping through the turbo. Scavenge pump pulled about 5 oz of oil in less than 10 seconds.

I tested the pump by disconnecting the return line and placing a pan under the sump. Then put 20oz of oil into a graduated container and placed the return line in the oil.

Removed scavenge pump from back of camshaft - drive pins are intact (minimal wear) and the two screw heads that actually engage the pump are undamaged.

The return line being swollen shut is an interesting proposition, the lines appeared fine on initial examination, but will look closer tomorrow.

AFJuvat

afterburn 549 · 05-23-2005, 08:33 PM

Yup......they can swell shut,hope thats it =ez fix...also make sure its plumbed back where it is suposed to be (no restriction)

dean · 05-24-2005, 05:38 AM

I don't know if you tried this or not.

Remove the turbo sump and let the oil drain into a pan and see if it still smokes. I would think the aftermarket sump with no vent is the problem.

dyerkes · dyerkes's Garage

Is 2% CO rich enough? I thought it should be 3%. I certainly recall when I had mine too lean, I could fry and egg on the bumper with only couple of seconds use. This is a real stretch, but do you know if the large ball bearing (900-108-022-00) is still intact on the pipe (930-107-338-00) that feeds from the oil drip tank to the crankcase. If not you certainly won't get proper oil flow.

You might want to also try posting on the 911Turbo board if you don't get a workable solution.

David
1986 911 Turbo

mmastro · 05-24-2005, 06:38 PM

I was thinking the same thing...2% CO is a little low. I was at 2.5% and my right bumperette melted onto my bumper and my paint started to darked and bubble. Set it at 4% and it settled at 3,8% and everything was fine (until I replaced the rear bumper w/ a RSR glass one)

cut some heat ducting holes and ThermoTec'ed the interior of the RSR bumper and viola, no problem!

RarlyL8 · RarlyL8's Garage

US spec motors are set at 0.5% CO to pass smog so that should not be an issue.

A faulty oil return line should not cause the motor to run so extremely hot. The oil will be forced out - somewhere.

Timing. A sticking advance will heat you up damned fast. Was the engine detonating?

mmastro · 05-24-2005, 07:21 PM

Low CO % would be an issue on this motor if it was timed and set like a US motor.....80-85 930's are Euro spec. Sure, some of them were federalised, but most were not done completely correctly. That's why most people took off the US spec (required) exhaust and either used a Euro setup or a cat (86-89) or an aftermarket system, and dumped the air pump/injection system.

Jim2 · Jim2's Garage

AFJuvat, the previous owner of my 930 mentioned a problem with a custom K27 which had a modified center section requiring an oil inlet restrictor orfice because the scavenge pump was unable to keep up. I doubt you would see two of these units (in a row no less).

The exhaust side overheating sounds like a separate issue. You would be surprised at how much the EGT will increase as a result of the timing being retarded by just a couple degrees. Ensure the distributer advance plate is not seized due to hardened grease. This is a very common problem with the 930 distributer.

Jim
79 930 (Solo I)

cstreit · cstreit's Garage

Question for you... does the engine slowly start smoking, or does it just open up the flood gates at a certain temp?

Sounds to me like there is too much oil-pressure and it's getting past the turbo seals somewhere...