I have a 1980 Turbo 4/4 that at least a couple of our esteemed Experts are familiar with due to its habit of burning copious amounts of oil when hot despite its low accumulated mileage of 12,000. In fact, at hot idle, it would do a WWII destroyer escort proud in laying down a smoke screen to shield the Allied convoy from enemy U-Boats were it called upon to do so!
The turbo has been rebuilt at least twice since it was suspected that it was leaking oil internally. A larger and more direct turbo oil return line was also fashioned, thinking the oil was pressurizing the turbo seal and bypassing it. Neither "fix" has made a wit of difference.
It has been suggested that rings seldom seat properly on propane, and I should need to re-ring the engine, though that propane characteristic has also been refuted by some. On this possibility, I need to preorder some new rings and a new head gasket at least. I might as well replace the big end bearings as well, though at 12,000 mi they should be like new. I just hate to reuse bearings once disturbed on principle. Would they be the same as on the last Ford Fiestas imported into the States for my 1980 Morgan Kent, or do I need to contact a specialty supplier for them?
At this point I need to do some experimenting myself. I was wondering if at idle it is safe to block the oil feed to the turbo for a while. Is the turbo spinning at idle, and if so, does it require more than residual oil for a 2-3 minute test run at idle only to see if with the oil feed blocked it would smoke?
Lastly, I have heard that it is necessary to separate the tranny from the engine block to remove the oil pan with the engine in place on these cars. Is this a fact or rumor?
Thank you all,
Bob Coviello
| FINK | SHEALLY II | WILLBURN |
Lorne,
I have a couple of suggestions in reference to Bob Coviello's
letter about his smoking turbocharged 4/4. There seem to me several
possible causes. He may have a broken piston or piston ring, which could
be
pinpointed with a compression leak-down test.
Turbocharged engines which smoke, particularly at idle,
often have a problem with the oil drain or inadequate engine venting which
leads to pressure in the oil pan and inhibits the oil drain return
to the
oil pan from the turbocharger. Oil accumulation in the
turbocharger will flow into the turbine (hot
side) and lead to smoking.
The 4/4 has a PCV valve in the side of the block which originally connected to manifold vacuum. In order to prevent pressurizing the oil pan on the turbocharged cars and blowing oil past the seals, we removed the PCV valve and routed the vent directly to the air cleaner. If that PCV valve has been refitted, it will prevent the engine from venting properly,leading to positive pressure in the crankcase, and preventing the turbo oil drain from working properly.
Further, if the engine has a sealed rocker cover, the cover should also be vented to the air cleaner.
In regards to blocking the oil flow to the turbocharger to observe any change in smoking for a brief period, it is likely that the turbine (hot side) has an accumulation of oil in it and along the walls of the exhaust system, which will continue to smoke long after the oil line has been disconnected.
We have never had a propane engine which smoked because
the rings which did not run in properly. The cars were run on gasoline
at the Morgan factory for test purposes before dispatch to us, which seems
to have taken care of any ring seating issues.
I am personally of the minimalist ("if it ain't broke, don't fix it") school of auto repair. Since it is likely that the problem is related to the turbocharger, before going further into the engine, replacing perfectly good bearings, head gasket, etc., I would be inclined to remove the turbocharger and route the exhaust through the system so that the car could be driven for a period of time sufficient to cook engine oil out of the exhaust ststem, muffler, etc. and see if it continues to smoke, indicating an internal engine problem with the rings or piston(s).
The oil pans on these 4/4's were not removeable without
pulling the gearbox, as the rear pan cap screws are hidden by a plate across
the lower part of the bell housing. Had they been removeable, we would
have fitted the oil drain to the pan above the oil level
and not routed it around the rear of the engine to the fuel pump block
off plate.
The best way to check oil flow through the drain is to replace the drain with a clear plastic line, and look for any accumulation in the line which will close off the passage to the pan and lead to pressure in the oil passage in the turbocharger, causing the previously mentioned smoking as oil flows into the turbine housing.
I hope some of the points made above will be helpful.
It seems to me that the most direct way to solve this mystery would be
to remove the turbocharger and drive naturally aspirated to see if the
smoking
disappears. If it does, then the other investigations
mentioned above would be appropriate. Failing piston or piston ring failure,
or a faulty turbocharger, it is likely a venting problem is impeding the
oil drain.
Should major engine work be undertaken, it would be a good idea to fit the oil drain to the top of the oil pan, above the oil level, to provide a straight run for the oil from the turbocharger.
Bill Fink
Isis Imports Ltd.
Bob,
You need to get some input from Bill Fink on your Turbo and or oil related possible problem. I would suspect a seal/"O" ring. I would not block of any oiling system.
I run a propane 83 Plus-8 (non-turbo) and have had three various engines in it in different stages of tune over the years and I can tell you that the advice on propane cars never have ring seal is pure "BS". Mine is in competition and has never given me ring/oil problems. All the engines have seated the rings very well.
What does bother me about your engine oil issue is that
it can stem from many causes ie. worn valve guides, broken ring or rings,
cracked ring or rings, worn rings, improper venting of the engine.... all
of which should not apply to a 11,000 mile engine unless you have run it
very hot at any time or times or
run it low on oil at any time. The items that I mention
here usually show up on high mileage engines.
Start by running a compression and leak down test. and
go from there.
I hope that this advice starts in the right direction.
Sincerely, John H. Sheally II
Lorne,
I am not that familiar with turbo Morgans, but:
1. Assuming that the turbo blows through the carb (instead of sucking), it should be possible to disconnect the hose between the turbo output and the carb input and see what happens.
2. Oil smoke at idle is more often from loose valve guides than from rings. If it is rings (and they are that bad), a compression check should tell.
3. I have not heard anything about rings not seating with propane. There are a lot of propane cars in California and they all seem to have properly seated rings.
4. Does it have power brakes? A leaking secondary seal will allow the booster to fill up with brake fluid and when it reaches the level of the vacuum input, oh what a smoke screen that makes.
Gerry