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Blowin' blue - how to diagnose cause

JDee

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First track day of the year today, got some really quick laps, new trans cooler seems to be keeping temps down, rebuilt trans working, well, like a new MT82 might be expected to work.

However, mid afternoon I got a black flag. Came in and they said the marshal station at turn 3 (outside of track on drivers left) had called in that my car was smoking, they weren't sure were it was coming from, they thought it was coming from underneath on the left side behind the rear wheel somewhere. They had noticed it earlier in the day but it got worse so they were concerned it was leaking oil.

Put it on the trailer and checked it over, no sign of leaks underneath from anything. That was my last session so we loaded up and headed home. Once home fired the car up to unload and a pretty decent cloud of blue smoke came out the left side exhaust. For sure it came out the exhaust pipe.

Engine sounds normal and runs fine, seemed to be making good power, I ran my 2nd fastest lap ever at Mosport. I checked my catch can, I usually get a couple of tablespoons per track day, but I dropped the thing, it's now sitting on the undertray so I am not sure how much oil was in it, going to take the tray off tomorrow and retrieve it.

My neighbour, who was there when I fired it up and saw the smoke is a long time garage owner, he speculated it might be leaky valve seals. So the question is how do you diagnose valve seals? I would think a compression test is useful to rule in/out ring/cylinder issues, but if that tests OK do I just put seals in and hope for the best? Appreciate any thoughts on what might be causing this.
 

TMSBOSS

Spending my pension on car parts and track fees.
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Valve seals "Usually" allow oil to pass with throttle closed. Vacuum is higher and oil is pulled past the valve seals. Open the throttle body diminishes smoke. Not always, but common.
Any codes?
 

JDee

Ancient Racer
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halfway between Mosport and Shannonville
Valve seals "Usually" allow oil to pass with throttle closed. Vacuum is higher and oil is pulled past the valve seals. Open the throttle body diminishes smoke. Not always, but common.
Any codes?
Nope. All normal. The marshal station they reported it from is partway through the corner around the area you'd be getting back into it. That corner is a right hander so left bank would be outside.
Also, it blew a big cloud on start-up so what would that mean?
 
Last edited:
1,115
1,082
In the V6L
First track day of the year today, got some really quick laps, new trans cooler seems to be keeping temps down, rebuilt trans working, well, like a new MT82 might be expected to work.

However, mid afternoon I got a black flag. Came in and they said the marshal station at turn 3 (outside of track on drivers left) had called in that my car was smoking, they weren't sure were it was coming from, they thought it was coming from underneath on the left side behind the rear wheel somewhere. They had noticed it earlier in the day but it got worse so they were concerned it was leaking oil.

Put it on the trailer and checked it over, no sign of leaks underneath from anything. That was my last session so we loaded up and headed home. Once home fired the car up to unload and a pretty decent cloud of blue smoke came out the left side exhaust. For sure it came out the exhaust pipe.

Engine sounds normal and runs fine, seemed to be making good power, I ran my 2nd fastest lap ever at Mosport. I checked my catch can, I usually get a couple of tablespoons per track day, but I dropped the thing, it's now sitting on the undertray so I am not sure how much oil was in it, going to take the tray off tomorrow and retrieve it.

My neighbour, who was there when I fired it up and saw the smoke is a long time garage owner, he speculated it might be leaky valve seals. So the question is how do you diagnose valve seals? I would think a compression test is useful to rule in/out ring/cylinder issues, but if that tests OK do I just put seals in and hope for the best? Appreciate any thoughts on what might be causing this.
Pull the spark plugs and look for fouling. That'll tell you a lot about what's going on inside the engine.
 
1,115
1,082
In the V6L
OK. But if they were fouled wouldn't it run crappy? It was running fine.
The high-powered ignitions in our cars can burn a spark through pretty much anything. It's the condition of the insulators that matters. If one (or two) are fouled, then there's a problem in the cylinder. If they're clean, then oil's getting into the exhaust without going through a cylinder. If they're all fouled, then there's oil in the intake. Taking the plugs out is the shortest way to some kind of information about what's going on. Engines with high oil consumption on a cylinder might pass a compression test, but the spark plugs never lie.
 
127
135
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3-5 Years
Arizona
Pull the air intake off and see if you have oil in the intake manifold, tube, or on the filter. I had all the same symptoms; smoke in a corner, smoke on next start, etc. It ended up being a gulp of oil going through the driver side PCV system into the intake.

GT500 valve covers with the improved baffling solved that issue.
 

JDee

Ancient Racer
1,516
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Exp. Type
W2W Racing
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20+ Years
halfway between Mosport and Shannonville
Pull the air intake off and see if you have oil in the intake manifold, tube, or on the filter. I had all the same symptoms; smoke in a corner, smoke on next start, etc. It ended up being a gulp of oil going through the driver side PCV system into the intake.

GT500 valve covers with the improved baffling solved that issue.

So I did this and checked the air flow through the PCV vents. Also started and shut down several times and no blue smoke out of the exhaust on start up so far.

On the right side (passenger) I have a JLT catch can which usually has 2 Tbsp of oil in it per track day, it again had some in it. That line sucks into the engine at the front of the intake manifold and it has strong suction, the engine is not happy with it open.

On the left side (driver) which (I believe) has the PCV valve in it, it runs out of the intake pipe very close to the throttle body and into the PCV on the left valve cover. With the PCV valve uncovered there is light suction on the PCV into the engine, it will hold a piece of film plastic on it and that's about all so not a lot of suction.

Just wondering if these things are sucking in the proper direction. Picture below hopefully clarifies this.
There was some oil in the intake pipe and throttle body that appeared to be coming from where the left side hose enters the intake tube. Not a lot, but enough to build up a tiny puddle in the bottom of the throttle body where it joins to the intake tube.

Could the PCV valve be bad or stuck open or something? Isn't that supposed to let fumes out of the engine to be burned in the intake? Tried to remove it but not sure how it comes out so rather than break it decided to wait for advice.

Mustang engine.jpg
 
The drivers side does not have a pcv in it. It is just an open nipple in the valve cover. Normal flow is from the intake into the valve cover (to replace waht's sucked out on the pass side) but the cover is known to collect oil as it has poor draining on the underside. This collection of oil can be "puked out" as mentioned above. The GT350 part has superceded the Coyote part number for the driver side cover, (as well as the GT500 piece).

To remove the PCV on pass side, use a wrench on the square area and on the dr side there is a hex at the base to unscrew.
 

JDee

Ancient Racer
1,516
1,542
Exp. Type
W2W Racing
Exp. Level
20+ Years
halfway between Mosport and Shannonville
The drivers side does not have a pcv in it. It is just an open nipple in the valve cover. Normal flow is from the intake into the valve cover (to replace waht's sucked out on the pass side) but the cover is known to collect oil as it has poor draining on the underside. This collection of oil can be "puked out" as mentioned above. The GT350 part has superceded the Coyote part number for the driver side cover, (as well as the GT500 piece).

To remove the PCV on pass side, use a wrench on the square area and on the dr side there is a hex at the base to unscrew.
Yep, I pulled it out and that's what it is, a hollow tube. Couldn't believe it. There is a very slight vacuum on the port that the hollow tube plugs into so that would be normal?

I don't think it was a single puke out situation though, the marshal at Turn 3 said she had noticed blue smoke earlier in the day and it got progressively worse to the point that she felt the car should be looked at. Hence the black flag.
The passenger side catch can always has about 2 tablespoons in it after a track day so no surprise that it had some oil in it. It was still blowing blue smoke on start up when I got it home and unloaded it, though today there is none.

I don't have a spark plug wrench that will get in there, working on getting one to see what they look like. Is there any point in putting a catch can on the driver side if it's already under vacuum?
 
Last edited:
127
135
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HPDE
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3-5 Years
Arizona
Yep, I pulled it out and that's what it is, a hollow tube. Couldn't believe it. There is a very slight vacuum on the port that the hollow tube plugs into so that would be normal?

I don't think it was a single puke out situation though, the marshal at Turn 3 said she had noticed blue smoke earlier in the day and it got progressively worse to the point that she felt the car should be looked at. Hence the black flag.
The passenger side catch can always has about 2 tablespoons in it after a track day so no surprise that it had some oil in it. It was still blowing blue smoke on start up when I got it home and unloaded it, though today there is none.

I don't have a spark plug wrench that will get in there, working on getting one to see what they look like. Is there any point in putting a catch can on the pass side if it's already under vacuum?
The passenger side valve cover has better baffling than the stock driver side valve cover. Not sure why Ford decided to make each side different. The driver side is intended to inflow only, but certain corners can allow oil to get into the breather line and it will go directly into the intake. Sounds like that's what happened to you.

The improved GT350 valve cover was backordered when this happened to me. I took a chance and ordered the aluminum GT500 valve covers and it has the improved baffling as well.

Oil witness in the intake tube, soaked my air filter and was leaking onto the ground.
IMG_8291.jpg

Passenger side valve cover on top, driver on bottom. Notice how the driver side "pickup" is at the back of the valve cover whereas the passenger side is near the center.
IMG_8512.jpg

The new valve cover baffle is a copy of the passenger side.
IMG_8493.jpg
 
1,115
1,082
In the V6L
Yep, I pulled it out and that's what it is, a hollow tube. Couldn't believe it. There is a very slight vacuum on the port that the hollow tube plugs into so that would be normal?

I don't think it was a single puke out situation though, the marshal at Turn 3 said she had noticed blue smoke earlier in the day and it got progressively worse to the point that she felt the car should be looked at. Hence the black flag.
The passenger side catch can always has about 2 tablespoons in it after a track day so no surprise that it had some oil in it. It was still blowing blue smoke on start up when I got it home and unloaded it, though today there is none.

I don't have a spark plug wrench that will get in there, working on getting one to see what they look like. Is there any point in putting a catch can on the pass side if it's already under vacuum?
So the PCV system works thusly:

Passenger's side - there is a one-way valve and a restrictor set into the valve cover. The passenger's side pipe connects from that assembly over to the intake manifold, where there's a strong vacuum most of the time in normal driving. That vacuum sucks crankcase gases out of the inside of the engine through the valve and the restrictor. Any oil droplets that get caught up in the air inside the crankcase are separated out first by the baffling in the valve cover, and second by the catch can you installed in the pipe that goes to the intake manifold.

Driver's side - the air that comes out of the crankcase on the pax side has to be replaced by fresh, clean air. This is provided by the pipe that goes from the duct ahead of the throttle body to the driver's side valve cover. Air in this duct has been cleaned by the air filter and metered by the MAF sensor, so there are no weird fluctuations in the AFR. All the driver's side pipe does under normal driving conditions is provide replacement air for the air that's sucked into the intake via the passenger's side pipe.

Now, at full throttle, the picture changes. There's no vacuum in the intake manifold - the throttle's wide open and manifold pressure is essentially atmospheric. So, there's no suction to pull crankcase gases out of the passenger's side, so the one-way valve closes and waits for the vacuum to come back. Every engine produces a certain amount of blowby, and since it can't get into the intake manifold via the passenger's side pipe, it flows "the wrong way" through the driver's side pipe and gets sucked into the fast-moving airstream ahead of the wide-open throttle body. The flow switches sides, but it gets into the intake manifold just the same.

So, the thing is, when you really generate high lateral G's, it's like laying the engine on its side. Oil gets up into the space in the cylinder head and stays there until the lateral G's drop and it can drain back down into the sump. If you turn right hard enough long enough, oil can find its way past the baffle in the valve cover and into the intake manifold ahead of the throttle body.

What this all means is that if you were on fresh tires and you were really rocking at full throttle and pulling high G's turning right (so oil would collect in the driver's side cylinder head) it's possible that you were just getting some oil flowing "backwards" through the duct and creating smoke.

A driver's side catch-can would fix this if it's the problem.
 

JDee

Ancient Racer
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halfway between Mosport and Shannonville
I have a 10 quart Moroso road race oil pan which they claim is accurate for fill with the stock dipstick. Could a small overfill of oil due to inaccurate dipstick reading and/or error in converting litres to quarts contribute to this problem? It sounds like it would not but just wondering.

Thanks for all the great input, I'm in the process of sourcing a drivers side oil catch can now and will look into the newer valve cover. Anybody know the part number for the new drivers side valve cover? I am seeing KR3Z-6582-C and it looks like it might be the newest one. It's $270 Cdn while the right side is $130 Cdn so I suspect this is the GT350 part.
 
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Could a small overfill of oil due to inaccurate dipstick reading and/or error in converting litres to quarts contribute to this problem? It sounds like it would not but just wondering.
I found they’re extremely sensitive to overfill. I was second guessing my oil level because of the way my oil cooler is mounted, and suspecting drain back would cause false readings on the dip stick. I added 1/2 quart during an oil change earlier this year, and first track day the car went into limp mode with the wrench light on the dash. Quick Google check was pointing towards a dirty throttle body, and sure enough when I pulled the intake tube there was oil pooled at the bottom of the blade. I’ve went back to the same fill level as before and no issues. I also replaced the Moroso passenger side catch can with the Watson Racing unit that vents both sides.
 

TMSBOSS

Spending my pension on car parts and track fees.
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I also replaced the Moroso passenger side catch can with the Watson Racing unit that vents both sides.
This is something to consider. I have the set up on my Boss. You can add or remove the system in minutes so you can remain "Street Legal" when on the street easily.
 

JDee

Ancient Racer
1,516
1,542
Exp. Type
W2W Racing
Exp. Level
20+ Years
halfway between Mosport and Shannonville
Ordered the new valve cover today, should be here on Monday. $270 canuck bucks for a valve cover, that was with a 10% discount from the local Ford dealer. Woof!
Also a driver side catch can is inbound, got that from Johnson Research and Performance, the folks who run the Speed Therapy track days and being a track day customer nets me another 10% discount. Gotta like those guys, they run a great track day at a low price and give us a discount on parts to boot.
 
JDee, I wish you well on your quest to get that blue smoke issue taken care of......with it coming out of the exhaust...it's gotta be engine related......that narrowed it down right........................................LOL................................good luck!!!!!!!!!!!!!!!!
 

JDee

Ancient Racer
1,516
1,542
Exp. Type
W2W Racing
Exp. Level
20+ Years
halfway between Mosport and Shannonville
What this all means is that if you were on fresh tires and you were really rocking at full throttle and pulling high G's turning right (so oil would collect in the driver's side cylinder head) it's possible that you were just getting some oil flowing "backwards" through the duct and creating smoke.

A driver's side catch-can would fix this if it's the problem.
Sorted through the data today and there were lots of 1.4 - 1.5 G corners after the warm up lap, peak was 1.57. I don't normally look at the G data so was surprised at that. This was on a set of Nankang AR-1's that had 2 track days last year, first one for this year. So that no doubt contributed. Hopefully, investing in the new valve cover and a catch can will get this under control. Thanks for your always helpful and detailed input, much appreciated.
 

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