[kittyboy]

Help please. Subject is potential excessive crankcase pressure damage and blown intake manifold seals. The following is a lot to read, but I wanted to provide as much information as possible. Thanks in advance!

Item #1 Condition:
Sporadic lean condition, wide band reads 16AFR for seconds at a time. Lean readings jump intermittently when accelerating at low and cruise rpms, sometimes lean continues until shifting into higher/lower gears, neutral, and idle. I stayed out of high rpm range to avoid lean and make it back to the garage. During the drive engine experienced no hesitation, seemed to operate normal, no high engine temps, no lean STFTs logged, no noises, logs did not reveal anything unusual.

Item #2 Condition:
Trace amount of engine oil discovered common to the oil drain plug area and lower bell housing/engine join vent. Couldn't 100% determine if oil migration originating from other areas. Borescope inspection revealed a possible trace amount of oil contamination internal bell housing. Valve cover breather had signs of oil blow-bye.

Possible Cause:
I replaced the passenger valve cover oil fill breather with a breather that has a 5/8" nipple for hose attachment, however I capped the breather nipple to avoid oil escapement from the nipple until time I installed the hose. I 'assumed' both 3/8" hoses to the catch can vented out a 5/8" hose to atmosphere would be sufficient for a couple short runs. Logged two short 5500rpm pulls and noted approximately 150hp and torque drop from previous logs. Returned home and performed an inspection.

Additional Information:
•GM B-15 long block (stock) 3k miles
•stock 1.9 SC with 3.6 pulley ratio
•1/2" phenolic plates installed between SC body and heads
•intake manifold port to valley capped
•3/8" drivers side valve cover port connected to Airaid inlet
•3/8" passenger side valve cover port connected to catch can
•3/8" valley crank case port connected to catch can
•5/8" catch can vent hose out to atmosphere
•oil fill cap replaced with breather type 5/8" hose to atmosphere
•1-2lbs less boost
•engine/oil temps 180-195*F normal
•no drops in oil press 30-53psi normal
•no drops is fuel pressure 50psi normal
•short term fuel trims, no lean or rich spikes recorded, 1.0-2.3% STFT averages
•O2s operating within normal range
•SC no unusual sounds based on previous stethoscope inspections
•engine start-up and idle normal, no rpm jumps
•engine operation overall seems normal less the current issues, no unusual sounds based on previous stethoscope inspections
•no knock or misfires logged both days
•belts (no slip), pulleys (no over heating), accessories all normal, no unusual sounds based on previous stethoscope inspections
•transmission normal operation
•worn clutch previously noted slipping (replacement planned)
•Added a can of RP engine cleaner to a full tank of 92 prior to issues, currently down to half a tank, most likely not a factor, just throwing it out there

Driving the past couple weeks the only other unusual issue that comes to mind is an occasional faint odor of burnt rubber in the area between the block and bell housing upon engine shutdown, drivers side. I checked belts and verified hose and header clearances, tires weren't the source, still undetermined source of burnt rubber odor?

My fear is I have managed to cause damage to my rear main seal? I already confirmed I blew my intake manifold seals via water test. The intake manifold seals are not stock, I have phenolic spacer plates installed using high temp RTV filled channels. I have a revised set of plates I plan to fabricate CMP-4000 (material) gaskets.

Some questions I have are:

1. Can a failing rear main seal cause a burnt rubber odor?
2. Why do my STFTs not register the unmetered manifold air leak as lean, even with a high hit count?
3. Is it best to completely remove the rear engine cover when replacing a main seal, and if so, is it good practice to remove and replace the oil pan gasket as well?
4. Opinions, Mcleod standard RXT vs RXT-HD?

So... What's the good or bad news anyone, compression, leak down tests, anything? Just trying to get some experienced feedback from the membership.

Thanks again for your help!

 

[Sudderth]

Sounds like the rings are going. I would do a compression check/leak down check to eliminate this as a possibility.

 

[kittyboy]

Sounds like the rings are going. I would do a compression check/leak down check to eliminate this as a possibility.

Hope not!

 

[Sudderth]

Me too, it is a cheap fix other than engine disassembly. A set of rings, a gasket set and a weekend of time doing the removal, disassembly, reassembly and reinstall. How many miles you got?

 

[kittyboy]

3k

 

[Sudderth]

wow, awesome low miles

 

[iviaillet]

Me too, it is a cheap fix other than engine disassembly. A set of rings, a gasket set and a weekend of time doing the removal, disassembly, reassembly and reinstall. How many miles you got?

There is no machine shop work required? I thought you had to deglaze the cylinders?

 

[Sudderth]

Just a bottle brush to knock down the glaze. and clean everything

 

[Sudderth]

 

[RocketSled]

Isn't there a check valve on the PCV breather, so compressed manifold charge can't go down the hose to the crankcase? Technically, I think it's there to keep a manifold backfire from exploding the bottom of the motor off. But in a blown car, it serves a dual purpose. When I added a Vortech to my 02 Z06, after maybe 20K miles of driving it started pushing the dipstick out when I really wound-out the car (centrifugal blower made max pressure at high RPM, little pressure at low RPM). No question it was too much pressure in the crankcase. Problem was that PCV check valve...

 

[Blown376]

Sorry about your troubles.

Go with a Monster LT1-S triple organic disk clutch. Operates just as good as OE and is rated for 1150 lb/ft.

 

[kittyboy]

Isn't there a check valve on the PCV breather, so compressed manifold charge can't go down the hose to the crankcase? Technically, I think it's there to keep a manifold backfire from exploding the bottom of the motor off. But in a blown car, it serves a dual purpose. When I added a Vortech to my 02 Z06, after maybe 20K miles of driving it started pushing the dipstick out when I really wound-out the car (centrifugal blower made max pressure at high RPM, little pressure at low RPM). No question it was too much pressure in the crankcase. Problem was that PCV check valve...

Thanks for the response. I recall one of the administrators informing me some time ago, that only a small percentage of the membership actually contribute to conversations. I know there is a wealth of information out there, too bad more don't contribute. So thanks again, I value your feedback! I'm by no means a seasoned expert at any of this!

Broadcasting personal failure to the world is brutal, use my current situation as example, "What Not To Do 101: Self Inflicted Destruction!" I'm still waiting to be lambasted, its a sport here. The price to pay for being an idiot while learning. (haha) But for the most part once the price is paid, the feedback is usually sound, solid, and sincere.

Keeping my fingers crossed that everyone goes a little easy on me this time around, I've suffered enough and hurt inside, I've no access to crisis intervention, no happy place to run too...

------

The following 'Rubber Duck' comment from another post was interestingly related:

"The above issue relates to insufficient 'Cylinder Seal'.

So while your attempting to increase 'Cylinder Fill' with your mods in order to generate
more HP, some of that 'Fill' is going to be wasted because of insufficient 'Cylinder Seal'. . . .

Running an engine on the 'Rich Side' using gasoline, can easily wash ring seal out. . .

Please be very cautious with your tune, as oil in the cylinders
greatly reduces your 'Effective Octane Rating'."

------

So far I'm leaning in your direction. I visualize excessive crankcase pressure expands 'balloons' the main seal causing excessive friction against the crank, burnt rubber odor, still not sure?

Still need to replace the manifold gaskets anyway, so once I have access, I will borescope the cylinders and valves, and perform a compression check. Might as well replace the plugs while I'm in there...

Still hoping to receive further feedback:

1. Can a failing rear main seal cause a burnt rubber odor?
2. Why do my STFTs not register the unmetered manifold air leak as lean, even with a high hit count?
3. Slipping clutch odor does not smell like burnt rubber, am I correct? At least in the past it hasn't.
4. Is it best to completely remove the rear engine cover when replacing a main seal? And if so, is it good practice to remove and replace the oil pan gasket as well?
5. Opinions, Mcleod standard RXT vs RXT-HD?

 

[Sudderth]

If you have a burnt rubber smell I would be checking on the belts and making sure no assessors drives are hanging up. Problem with the rear main seal is that it is one piece and that means the transmission has to be removed enough to get the torque converter away from the flex plate and then the one piece seal can be removed and reinstalled. If yours in a manual it means the clutch and flywheel has to be removed. Way back when I worked at Chevrolet we had super long bolts and used two to hold up the transmission while replacing the rear main seal. Easier to get the transmission back enough to do the replacement than it is to remove the engine. If the pan gasket is not leaking there is no reason to replace it. Also, it bears mention that the pan gasket is a great product and most do not leak. I do not have a preference on the Mcleod products. What makes you happy works. I think the range is not so far out of range to throw a code.

 

[kittyboy]

If you have a burnt rubber smell I would be checking on the belts and making sure no assessors drives are hanging up. Problem with the rear main seal is that it is one piece and that means the transmission has to be removed enough to get the torque converter away from the flex plate and then the one piece seal can be removed and reinstalled. If yours in a manual it means the clutch and flywheel has to be removed. Way back when I worked at Chevrolet we had super long bolts and used two to hold up the transmission while replacing the rear main seal. Easier to get the transmission back enough to do the replacement than it is to remove the engine. If the pan gasket is not leaking there is no reason to replace it. Also, it bears mention that the pan gasket is a great product and most do not leak. I do not have a preference on the Mcleod products. What makes you happy works. I think the range is not so far out of range to throw a code.

That's good news regarding the oil pan gasket, the pan is a pain to remove due to cradle clearance. When I installed the pan I applied a small amount of sealant at forward and rear engine cover joins. Suppose it would be good then to remove the old sealant and apply some fresh sealant at these same locations? What are your thoughts about removing the rear engine cover to replace the rear seal vs fishing it out? I'm thinking it couldn't hurt to hand polish the crank/seal contact area if in fact it has been experiencing friction? Fortunately, I was already planning to remove and replace the manual clutch. I checked all the accessories, pulleys and belts, the all check excellent.

Just clarifying, so even if the seal has previously experienced friction wear, but not leaking, it should still be ok to use?

 

[RocketSled]

Seals depend on very tight tolerances in order to do their sealing thing (which I admit is kind of obvious). If you had a seal making enough friction you could smell it burning, the seal will have failed completely by the time you even notice it. Oil should be flowing out the back of the motor like there wasn't any seal there at all, which if it burned even a little, there wouldn't be...

 

[Kjwhit]

Time for rebuild in my opinion this is what happened to me kept blowing gaskets read main seal then oil pan and I kept throwing money at bandaids until my motor told me I ripped apart 4 pistons

 

[kittyboy]

Seals depend on very tight tolerances in order to do their sealing thing (which I admit is kind of obvious). If you had a seal making enough friction you could smell it burning, the seal will have failed completely by the time you even notice it. Oil should be flowing out the back of the motor like there wasn't any seal there at all, which if it burned even a little, there wouldn't be...

I've not a clue whats normal is when it comes to the seals, I worry too much, I know, thanks for the info. Anyway, just returned from the garage after borescoping some of the other surrounding areas. Turns out I have a blown drivers side valve cover gasket, (see attached images). Do you think the crank case pressure had anything to do with the blown valve cover gasket and manifold leak? Thanks...

I tested some motor oil on tin foil and torched it, the smoke odor is identical to what I previously believed to be burnt rubber. Turns out a small amount of oil is migrating from the lower driver side valve cover to the oil pan, along the way the headers are cooking some of it. So that confirms the burnt rubber odor and trace oil near the bell housing. I've begun to repair the intake manifold leak.

 

[kittyboy]

Time for rebuild in my opinion this is what happened to me kept blowing gaskets read main seal then oil pan and I kept throwing money at bandaids until my motor told me I ripped apart 4 pistons

What exactly was wrong with the pistons?

 

[kittyboy]

After some additional thought, maybe I actually didn't have an excessive crankcase pressure failure after all? I'm now thinking it may be possible leaking exhaust heat from the header manifold caused the valve cover seal to deform and leak oil? Has this happened to anyone? Appears the header exhaust manifold mounts very near where the seal failed, doesn't appear to be 'blown out' just deformed. Also, there isn't a drop of oil where the dip-stick inserts into the block. So maybe that's why I smelled burnt rubber?

 

[Kjwhit]

What exactly was wrong with the pistons?

Umm torn all apart 😂 best bet would be to check all your spark plugs you’ll see if there’s any damaged to them from broke apart pistons atleast you’ll know ….mine had to be happening for some time because I was replacing every seal thousands and thousands of dollars and then I had to do the rebuild anyway and replace all those seals again, it was fun