TROUBLE SHOOTING
SMOKING EXHAUST:
There are many things that could cause your exhaust to smoke.
Our objective with this article is to assist enthusiasts in diagnosing
and resolving the actual problem quickly rather then going through an expensive
and time consuming “process of elimination” method to resolve the issue.
We hope the information in this guide sheds some light on possible sources
of the oil, causes of the oil’s introduction in to the exhaust system and
finally, the solutions available to correct the issues.
Whether your turbo is new, rebuilt or has been on your car for a while,
here are just a few solutions to some common problems which might save you the
trouble of pulling the turbo off only to have the same problem after it has
been replaced:
#1
Existing oil in exhaust system still burning off from previous turbo
failure.
Many times when turbochargers fail they dump considerable amounts of
oil in the exhaust system. You can try to flush it out or continue
to run the car until the smoke disappears, but, this can take days.
Plan on replacing your catalytic converter soon because burnt oil will
quickly restrict air flow impeding performance. This can quickly lead
to other problems down the road including turbo failure.
#2
Smoke is present at Cold Start Up
If your engine smokes immediately after a cold start the problem is most likely
not the turbo. The only place hot enough to turn oil into smoke during a cold
start is the combustion chamber. You need to focus on the intake valve seals,
guides or piston rings as the source of your oil. Check your spark plugs and
intercooler hoses for signs of oil also. Complete a compression and leak down test
to determine the overall condition of your engine.
#3
Exhaust Valve Guides or Seals
If the spark plugs are clean and the exhaust does not smoke until after the vehicle
is warmed up the source of the oil may be the exhaust valve guides/seals. We have
seen several incidents where the guides/seals were improperly machined on freshly
built cylinder heads. Don't discount this possibility just because your cylinder
head was recently rebuilt.
#4
Oil or blow-by pressure build up in Turbo Bearing Housing.
Turbo oil seals are usually made of carbon and, much like a single piston seal,
there is a gap that oil can seep through when pressure is present. Pressure
build up can be caused by one or more of the following reasons:
a) Blockage in drainback hose/tube.
Verify there are no foreign objects in the drainback hose/tube.
This could be the paper towel or duct tape you placed there during the
removal of your original turbo to prevent debris from falling in to your
oil pan during the swap.
b) Using wrong type of drainback hose.
Not using the factory silicon drainback hose is a common mistake. Silicon
hoses are heat and oil resistant where most standard heater hoses cannot
withstand these extreme conditions for very long. Most standard hoses
are actually 2-3 hoses separated by braided nylon. When
this is used in place of the silicon hose the nylon can actually shrink
when exposed to heat restricting the inner hose while leaving the exterior
hose looking perfect from the outside. Use the factory orange silicon hose
whenever possible or one of our blue silicon replacement hoses. There are
no advantages to using any other type of hoses for this application. Turbo
removal not required. Once issue is addressed piston seals should reseat
on their own and oil seepage will no longer be a problem.
c) Oil return flange gasket issues
This is a “dry” gasket so do not use RTV on it. Even the slightest bit that
may get squeezed into the flow of the return oil will impede the gravitational
flow of oil back into your oil pan. Oil pressure will build up in the turbo bearing
housing to the point where oil is pushed past the seals. Remove all RTV from the
area and replace the gasket. Seals will reseat on their own.
d) Wrong oil drainback line angle.
Turbo oil drainback is powered only by gravity. Angles in excess of 20
degrees will impede oil return flow and pressure build up in the bearing
housing may result. Also be sure to maintain a smooth curve from turbo to
engine and prevent any kinks in the line which may cause a back-up and
eventual pressurization of the bearing housing.
e) Oil feedline pressure exceeds drainback tube capabilities.
Verify oil pressure is not excessive. 60 PSI at idle for a
warmed up engine is WAY too much. 10psi per 1000 RPM is a good rule of
thumb. Any more pressure is robbing your engine of HP. Too much oil can
pressurize the turbo bearing housing if the gravity fed drainback cannot
keep up. This pressurization will force the oil past the turbine shaft
piston seals and into the exhaust or compressor side of the turbo. Over
time, too much pressure can actually be harmful to your entire engine.
With excessive pressure, impurities in your oil can actually eat away at your
bearing surfaces and increase tolerances much like extrude honing works.
Don't use the MP Oil Pressure Relief Spring Kit or Mellings High
Volume/Pressure oil pump. TU strongly advises against High V/P pumps.
Turbo removal not required. Once issue is addressed piston seals should
reseat on their own and oil seepage will no longer be a problem.
f) Blow-by in crankcase caused by worn engine, cracked pistons,
rings, faulty PVC systems, etc.
Crank cases pressurized by blow-by can also cause oil to be forced past
the turbine shaft piston seals. Complete a compression check and leakdown
test to check the condition of your engine. There is also a blow-by
detection tool which is placed over the oil cap opening while the engine
is running and measures crank case pressures. Be sure to inspect your
crank case evacuation system to make sure the issue is not being caused by
a bad PCV valve. If you find your oil dipstick out of the tube a few inches
after some spirited driving you are most likely experiencing blow-by.
Once issue is addressed piston seals should reseat on their own and oil
seepage will no longer be a problem.
g) Chrysler Valve Cover Oil Baffle TSB
There was a Chrysler TSB in the late 80’s pointing out that some Turbo Valve
Cover oil baffles were not sealed properly. Oil was being drawn through the
baffle from the bottom and being drawn into the PCV and air filtering system.
Removing the VC baffle and resealing it with RTV resolved the problem.
A few people have modified and installed a TBI VC inner cover which also helps
reduce the chances that oil will be drawn into the PCV system.
For some, the turbocharger is still the mysterious “black box”
which isn’t fully understood. Because of this, it is usually looked upon first
when exhaust smoke is present. As we pointed out in the above examples
the turbo may be the source of the oil, but, in most cases it is only the
result of the problem and not at fault. Once corrective actions are taken
the issues can be resolved without the expense and labor of removing and
replacing the turbocharger. This list is constantly growing and we will
continue to add to it as we come across new issues and testing methods.
Also, we strongly discourage decreasing or limiting the amount of oil
pressure to the turbo in order to confirm that it is the source of oil.
If the turbo wasn’t bad before the test it soon will be as metal-to-metal
contact will take out a turbo in a matter of seconds.
If you have any questions about the above information don’t hesitate to contact us.
GOOD LUCK!
Chris-TU
602-76-BOOST
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