severe vacum problem some how entering engine.

Asked by Dec 11, 2014 at 09:50 PM about the 1998 Chevrolet Monte Carlo 2 Dr Z34 Coupe

Question type: General

i have a 98 monte carlo z34.as some others commented,i can feel tremendious
suction taking off oil cap and if i pull it off real quick ,it sometimes dies.i replaced
pcv valve and sprayed all aroun intake and plentium with starting fluid and no
changes.i had a bad map before and changed it, and then had a front main seal
leaking,i replaced it.it still leaked.i changed harmonic balancer and changed seal
again,twice,and its still leaking,but not as bad,but too much.i did compression
check.2 cylinders at 155 all others 165.i did not have the vacume problem until
recently.i had checked for blow-by and rempving cap made no engine changes as
far as running.What is goin on here.the diagnostic check sad some mis-fire and
idle sensor.sometimes when i start it, it will act like it hesitates some and i also
get some weird engine sounds when cap is off.Does this O ring i have heard
about go ender the pcv valve,or is it the inch sized red one under the plastic twist
cap that holds the pcv valve and spring in place.Please help.Sincerely,Robert
Andrews

12 Answers

58,375

Robert,if it has suction,this would lead to the intake gasket,spraying around the out side of intake will on find a out side leak,not and internal leak,and yes i know you did a compression check on the cylinder,s,but did you do it with the oil cap off?A internal leak on the in take will draw suction,and cause this issue.

1 out of 1 people think this is helpful.
77,925

T S T is correct about an intake leak, but have you checked the PCV fresh air intake tube, it could be collapsed or plugged.

1 out of 1 people think this is helpful.

i checked it with oil cap on.and i have not checked line inside of plentium,as ther is not an extewrnal one except for the one that goes,ok yeah the two external ones goin either to throttle body,it is good the other goes to fresh air and looks good.are you talking about the line inside the plentum?i will check all them again.i have been afrain intake gasket might be bad,but it woul have to be the lower intake wouldnt it?considering it is coming from top of the head.thank you.pleSE REPLY,.sINCERELY,rOBERT aNDREWS,P.S.I REBUILT THIS ENGINE ABOUT 30,000 MILES AGO,AND COULD THIS ALSO CAUSE FRONT MAIN SEAL LEAKAGE,tHANK YOU ALL VERY MUCH.

77,925

If you have as much vacuum that you say you do it can pull open all of the seals while it is running. It would be the lower intake that would be leaking.

1 out of 1 people think this is helpful.

OK, ILL CHECK IT OUT,THANK YOU

BEFORE I DO ALL THIS WORK,I FIGURE IT WOULD BE BURNING ALOT OF OIL,BUT IT ISNT?ITS VERY WEIRD.IF I PULL PCV VALVE OUT WHILE RUNNING IT DOESNT HAVE VACUM PULLING THROUGH OIL CAP,SO IT DOES SEEM LIKE INTAKE,BUT JUST DONT UNDERSTAND IT NOT BURNING OIL AND SMOKING.IF ANYONE ELSE HAS ANY OTHER COMMENTS PLEase HELP.i am very grateful.Thank you all very much.

77,925

It won't burn oil if it is just the intake gasket as they usually fracture into the valley and there is very little oil up there. You answered mt next question about vacuum with the PCV valve out. So the only thing it can be is something blocking the filtered fresh air intake for the PCV valve, also check the valve itself, make sure it rattles a little when shaken and is clean.

1 out of 1 people think this is helpful.
Best Answer
77,925

Thanks

thank you so much,i was hoping this was not the case,but i feared it.thank you for your fast reaction to my questions.

77,925

As you can tell it is very hard to try to diagnosis without a hands on but we try, I hope it is not as deep as you think it is. Good Luck.

where is the filtered fresh air inlet for the pcv?you know it is set up with pcv down inside plentum and the map connects on top of that,and then the wiring plugs into map.you have the vacume condenser ball under driver fender then the othar that hooks to the throttle body.is the throttle body,supposed to hook up to the vacume line that chambers off to the vacume condenser ball.?

77,925

There should be a tube that comes from the fresh air tube that runs to a valve cover so itrovides filtered air into the engine as the PCV demands it. Some vehicles had it on the throttle body just in front of the air valve plate.

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