Possible Leak - Engine Smoking - ZR-1 Net Registry Forums

hottrodcrazy · 08-26-2013

Please give you advice on a problem I am having. I just bought a 1991 ZR1 with 6000 miles. I haven't really driven it yet, but when I start it up and it gets warm enough it starts smoking below plugs 4 & 6. I can't see where it's coming from and don't find any leaks on the ground below the car. After a few minutes it burns off and stops smoking, but I have started it several times and it continues to do this. I'm guessing it's probably a small oil leak, but again, I can't find actual evidence or the location of a leak.

Does anyone have any ideas? Thanks.

XfireZ51 · 08-26-2013

Anything out the back? Oil or coolant? May be header stud leaking oil.

hottrodcrazy · 08-26-2013

There is possibly a little smoke coming out the back. I thought possibly that could just be exhaust. I'm not sure if it's oil or coolant, it doesn't smell like oil and I'm not exactly sure what coolant would smell like.

Sorry, I don't have better answers to the question. I appreciate the help, I just know that I'm getting some smoke, can't tell what type of smoke it is and as I said previously, can't see evidence of where it's coming from. Thanks again.

Franke · 08-26-2013

The ZR-1 Net Registry has info on oil leaks for the LT5 Engine. I think Xfire may be spot on here.
An excerpt from the tech articles "If you have a leak coming from the center of the engine, seemingly from the exhaust manifold, you might be correct. On some engines, the center studs for the exhaust manifolds are drilled into or nearly into an oil passage. Eventually, the oil works it's way through the stud's threads, causing a leak. Removal of the stud and the application of a sealer usually resolves this problem."
You might want to check the Registry for additional causes of oil leaks.

Paul Workman · 08-27-2013

Coolant "smoke" is actually steam, "white fog" and you may, depending on one's olfactory acuity, detect the smell of antifreeze...but not always.

I had a leak on the afore mentioned exhaust manifold bolt; same side too, as it happens. And, I believe too that the FSM is where I read to use some RED (aka high-temp) RTV on the threads and re-seat the bolt. (It fixed my leak!)

If you see blue-ish smoke, it is oil. And, if blue, and smells like burning oil...likely it is.

If you turn the engine off, after it gets hot enough to cause the smoking, and the smoke continues to rise from the 4-6 cylinder area, well that is directly above the afore mentioned header bolt.

FWIW,

P.

max76 · 08-28-2013

Quote:

Originally Posted by hottrodcrazy

Please give you advice on a problem I am having. I just bought a 1991 ZR1 with 6000 miles. I haven't really driven it yet, but when I start it up and it gets warm enough it starts smoking below plugs 4 & 6. I can't see where it's coming from and don't find any leaks on the ground below the car. After a few minutes it burns off and stops smoking, but I have started it several times and it continues to do this. I'm guessing it's probably a small oil leak, but again, I can't find actual evidence or the location of a leak.

Does anyone have any ideas? Thanks.

Hi hottrodcrazy,
the 4&6 plugs are on passenger side? If yes i have the same problem.
I try to go under the car but i cant see where is the leak. I think is oil leak from the odor.
Do you solved the problem???
How???
Thanks
Max

hottrodcrazy · 08-29-2013

Max, I haven't had a chance to investigate the problem further yet, so no I have not fixed it. Yes, plugs 4&6 are on the passenger side. It sounds like my problem, except that mine doesn't smell like an oil odor. It often smells like burning rubber, but not oil. I would suggest if you haven't read the suggestions above you read what the others have to say, I feel like it's probably as suggested that it's a header stud leak. Good luck with your issue!

max76 · 08-29-2013

Thanks hottrodcrazy...

Franke, how i can remove the stud???There's a nut to unscrew??
Thank you so much
Max

Franke · 08-29-2013

Max, I've never performed the stud removal procedure. I think your going to need the service manual and maybe some one on this forum who did it before could help with additional info.

A26B · 08-29-2013

The nut is "self locking" 15mm hex drive, threads are M10-1.5.

If the stud has been leaking, it will frequently come out when you attempt to remove the nut.

If the stud does not come out with the nut, then obtain 2 standard, M10-1.5 nuts and double nut the stud to remove.

08-26-2013	#1
hottrodcrazy Join Date: Apr 2013 Location: North Carolina Posts: 22	Possible Leak - Engine Smoking Please give you advice on a problem I am having. I just bought a 1991 ZR1 with 6000 miles. I haven't really driven it yet, but when I start it up and it gets warm enough it starts smoking below plugs 4 & 6. I can't see where it's coming from and don't find any leaks on the ground below the car. After a few minutes it burns off and stops smoking, but I have started it several times and it continues to do this. I'm guessing it's probably a small oil leak, but again, I can't find actual evidence or the location of a leak. Does anyone have any ideas? Thanks.

08-26-2013	#2
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Re: Possible Leak - Engine Smoking Anything out the back? Oil or coolant? May be header stud leaking oil. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

08-26-2013	#3
hottrodcrazy Join Date: Apr 2013 Location: North Carolina Posts: 22	Re: Possible Leak - Engine Smoking There is possibly a little smoke coming out the back. I thought possibly that could just be exhaust. I'm not sure if it's oil or coolant, it doesn't smell like oil and I'm not exactly sure what coolant would smell like. Sorry, I don't have better answers to the question. I appreciate the help, I just know that I'm getting some smoke, can't tell what type of smoke it is and as I said previously, can't see evidence of where it's coming from. Thanks again.

08-26-2013	#4
Franke Join Date: May 2013 Location: Beaver, PA Posts: 516	Re: Possible Leak - Engine Smoking The ZR-1 Net Registry has info on oil leaks for the LT5 Engine. I think Xfire may be spot on here. An excerpt from the tech articles "If you have a leak coming from the center of the engine, seemingly from the exhaust manifold, you might be correct. On some engines, the center studs for the exhaust manifolds are drilled into or nearly into an oil passage. Eventually, the oil works it's way through the stud's threads, causing a leak. Removal of the stud and the application of a sealer usually resolves this problem." You might want to check the Registry for additional causes of oil leaks.

08-27-2013	#5
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Possible Leak - Engine Smoking Coolant "smoke" is actually steam, "white fog" and you may, depending on one's olfactory acuity, detect the smell of antifreeze...but not always. I had a leak on the afore mentioned exhaust manifold bolt; same side too, as it happens. And, I believe too that the FSM is where I read to use some RED (aka high-temp) RTV on the threads and re-seat the bolt. (It fixed my leak!) If you see blue-ish smoke, it is oil. And, if blue, and smells like burning oil...likely it is. If you turn the engine off, after it gets hot enough to cause the smoking, and the smoke continues to rise from the 4-6 cylinder area, well that is directly above the afore mentioned header bolt. FWIW, P. __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry Last edited by Paul Workman; 08-27-2013 at 06:55 PM.

08-29-2013	#7
hottrodcrazy Join Date: Apr 2013 Location: North Carolina Posts: 22	Re: Possible Leak - Engine Smoking Max, I haven't had a chance to investigate the problem further yet, so no I have not fixed it. Yes, plugs 4&6 are on the passenger side. It sounds like my problem, except that mine doesn't smell like an oil odor. It often smells like burning rubber, but not oil. I would suggest if you haven't read the suggestions above you read what the others have to say, I feel like it's probably as suggested that it's a header stud leak. Good luck with your issue!

08-29-2013	#8
max76 Join Date: Apr 2009 Location: ITALY Posts: 264	Re: Possible Leak - Engine Smoking Thanks hottrodcrazy... Franke, how i can remove the stud???There's a nut to unscrew?? Thank you so much Max

08-29-2013	#10
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Possible Leak - Engine Smoking The nut is "self locking" 15mm hex drive, threads are M10-1.5. If the stud has been leaking, it will frequently come out when you attempt to remove the nut. If the stud does not come out with the nut, then obtain 2 standard, M10-1.5 nuts and double nut the stud to remove. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.