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Source of Oil Burning Smell

new 12/28/2003

Hopefully some people are still around and checking their e-mail. I found the source of the "burning oil" smell in my car this morning. Popped the hood, and it looks like the lines are leaking at the "Tee" right above the Throttle Body. I believe these are vacuum lines? In any case, there is an oily substance leaking onto the TB, engine, and appearance cover at that Tee right by the TB.

I pulled the vacuum(?) line off the intake "duct" by the MAF, and the connector was coated in a dark oily substance.

So, the question is, what could/would cause this? It didn't/doesn't smell like gasoline, and I don't have problems starting the car, but I have a 280 mile trip to take in 8 hours, and I want to make sure I'm going to get there in one piece.

Any help that can be offered is greatly appreciated!!!

-John "I better make it home for Christmas" Breen III

Those lines are part of your pcv system. The left hose goes to your front valve cover, the hose pointing towards your firewall goes to your rear head valve cover. The right hose goes to your MAF Flex Pipe and pulls vacuum on the other two hoses.
The tee fitting is plastic and I have seen several of these broken. So much so that I just keep a handful of 3/8" tee barbs in my garage. Those hoses LOVE to split on motors over 100k too. 
It's either your tee (My bet) or your hose leaking. It is normal to have some oily deposit IN the hose but not to leak OUTSIDE of the MAF hose. That oil in these hoses is what eventually goes through the throttle body and ends up caked on your lower intake Butterflies. That tee is a perfect splice point for Paul's PCV catch can. Just add some 3/8" hose and a couple of barb to barb splices and run the hose to the can.

Eric Lehmann 

Eric, with all due respect, both you and Kirk are misinformed as to how the normal PCV system works. By normal I mean one with a PCV valve.

>The right hose goes to your MAF Flex Pipe and pulls vacuum on the other two hoses.

>its designed as a FRESH AIR IN but the vacuum from the motor pulls from there all the time.

The PCV system has a exhaust (low pressure/vacuum) side and an atmospheric side. The low pressure side is the intake manifold and is regulated by the PCV valve. On the V8 SHO this is the hose that enters the intake near the EGR valve. The PCV valve will act as a check valve (not 100%) that will prevent the flow of air from going from the intake to the crankcase and as a vacuum regulator. Normal flow is from the pre-TB/post MAF intake, to the valve covers, to the crankcase, out the oil separator, to the intake manifold through the PCV valve and into the cylinders.

The hose that feeds this system or supplies the fresh air is the hose that is after the MAF (so it is measured) and before the TB (so it is still near atmospheric pressure) and connects to the valve covers. It is the throttle plate in the TB that ultimately determines the amount of vacuum behind it and in the intake manifold. There is not what you would really call vacuum before the Throttle plate, only a lower than atmospheric air pressure level. You would have to measure this with a barometer or a manometer and not a vacuum gauge. 99% of the time the crankcase is slightly under atmospheric pressure. EXCEPT at WOT. At WOT there is no intake vacuum level, therefore the sub-atmospheric pressure found in the pre-TB intake combined with the pressure in the crankcase caused by blow-by gasses will force the oily blow-by into the pre-TB intake.

The purpose of the PCV system is to purge the crankcase of these blow-by gasses which pass by the piston compression rings and into the crankcase. These gases would dilute and contaminate the oil if allowed to remain in the crankcase. This happens with all cars but the older and more carboned up the piston rings the worse it is.

Here is a picture of the normal flow of the PCV system at all times except at WOT.

At WOT the flow will reverse but with a lot less volume of gas. This is limited by the PCV valve acting as a check valve (preventing the gasses/air in the intake manifold from flowing backwards toward the crankcase) and the amount of pressure created in the crankcase by blow-by.

To check the performance of your PCV system, at idle, disconnect the hose going to the pre-TB intake hose and put your thumb over the hose going to the valve covers. There should be a slight build up of vacuum. As a matter of fact on the GEN 3 V8 there should ultimately be a 7" to 10" Hg vacuum build up.

Paul Nimz
'97 TR

There is a constant draw on the PCV line (one with the Valve) under normal driving (which draws oil vapors in to the tank.

The Valve cover lines are the Fresh air or make up lines to give the crank case air.

Under WOT or no vacuum, the PVC side does nothing and the Valve cover lines then draw in the oil from the air passing through the TB creating a vacuum pulling the vapors out though yet another oil separator per each valve cover. 

Causing the oiling effect that John is getting, but the system will reverse 100 percent if the PVC valve gets clogged and it draw out of the Valve covers under normal driving.

This is why the second line on the back side of the rubber Maf to TB is also connected to the Brakes and a few other things. So they still have a vacuum at WOT 

Kirk J Doucette

I guess it depends on your definition of vacuum. I consider vacuum anything at or above 1" Hg on a vacuum gauge. True there is low pressure in the pre-TB intake but it is comparable to the difference in air pressure from in front of your car to the rear of the car when driving. Somewhere in the range of under 1" of H2O and you would need a manometer to read the pressure difference. 1 inch of mercury = 13.5951002 inch of water 

The lines that are connected to the pre-TB intake are not for vacuum when the intake is at WOT. This is the job of the reserve vacuum tanks in the fender. Seldom are you at WOT and in need of the power brake booster. The purpose of the large hoses going to the small manifold on the firewall is to supply fresh air for the fuel vapor recovery and to vent the power brake booster when needed as it operates both on vacuum and atmospheric pressure.

If the pre-TB intake PCV hose's purpose was to vent the crankcase there would be a bad build up of gunk on the throttle plate. Again if you just eliminate this hose connection and connect the two valve cover hoses together the problem is 100% eliminated and a slight performance/fuel economy gain is seen.

Paul Nimz
'97 TR


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