HUGE vacume on oil filler cap S1 2.8. Please advise!

[0038VX]

Hello there,

I'm getting my '88 S1 2.8 ready for the summer. While doing i discovered a hissing sound from the oil filler cap. When I removed it the engine would stall and eventually stop running. When I placed my hand on the opening it allmost got sucked into the engine. The vacume is so big that if I had a girlfriend capable of creating that, I would probably give up cars and never leave the house

Please advise as I'm about to replace the engine..

[GreenV8S]

It's normal for cars with a recirculating breather system to have a slight depression in the crank case at idle. The typical layout is a twin breather system with one outlet connected downstrean of the throttle via a restrictor and a second larger outlet connected upstream of the throttle. From memory the V6 S series usually have this connected into the back of the air cleaner, but this may not be universal. From your description you are getting a lot more flow through the restricted outlet than normal and it may be that somebody has removed or opened out the restrictor. One reason to do this might be if the second, bigger outlet has become blcked. So this would be a good time to check the state of the whole breather system to make sure it is all connected and none of the hoses are blocked.

[0038VX]

'k I checked all the hoses and intakes for anything blocking them.. but without results. I also figured out that this huge vacume is appearing when the engine is et iddle. Later today a freind told me that this might have something to do with the injectors being dirty or blocked?

[GreenV8S]

0038VX said:

this might have something to do with the injectors being dirty or blocked?

Don't see how that could be related. As far as I can see, it's purely a breather problem.

[tvrgit]

would a breather problem not tend to blow OUT? and then those gasses are drawn back into the air intake and burnt?

high suction at the rocker cover wouldn't be normal surely? The rocker covers aren't connected to the "upside" of the throttle butterfly. air shouldn't be getting sucked into the engine through the rocker cover, bypassing the throttle, to the extent that the engine stops when you take the oil cap off!

I am thinking where this suction could be coming from. The only thing I can think of is badly worn inlet valve guides - does the engine smoke when you reapply the throttle after engine braking?

[GreenV8S]

Under load the breather gasses are blown out upstream of the throttle, off load they are sucked out via the restriction downstream of the throttle. The symptoms here indicate that the restrictor isn't being very restrictive. One possible reason is that somebody has removed it or opened it out to bodge round a problem with the other breather outlet.

[0038VX]

GreenV8S said:

The symptoms here indicate that the restrictor isn't being very restrictive.

Tnx V8S, this may sound stupid.. what does the restrictor look like.. I did some googling but ended with no results or pics..

This is the first car I own that has fuel injection.. never had to work on it..

[Le TVR]

0038VX said:

Hello there, While doing i discovered a hissing sound from the oil filler cap.

Not the o-ring perished??

0038VX said:

When I removed it the engine would stall and eventually stop running.

Quite normal.

0038VX said:

When I placed my hand on the opening it allmost got sucked into the engine. The vacume is so big that if I had a girlfriend capable of creating that, I would probably give up cars and never leave the house

Given the size of the filler cap, even a reasonable depression value would seem like serious suck

[0038VX]

Thanx both Le TVR and Green V8S, But the depression is abnormally high it can't be normal. It allso makes the little valve on the rocker cover to the inlet housing whistle when I release the throttle

[0038VX]

I think I have figured it out.. It's the gasket between the shortblock and the inlet manifold. Took it all apart today and noticed some cracks in the gasket. While everything detached I can do some cleaning and adjust the valves as well. It's gonna run as new when I'm finished!!