What could be?.

I did a valve adjustment and all is O.K. (I think):

But the last strange condition is: The engine oil dipstick tube has vacuum in it, with the engine running. No coolant or gas into the engine oil. It's normal? Could be the PCV valve?. Bad or incomplete adjustment process?.

Thanks for the help,

Denis V.

 

check the breather to see if its clogged and also check the pcv valve to make sure its not stuck open.

 

remove and plug the pcv valve.

check for vacuum at dipstick tube.

if vacuum still exists check and plug breather tube.

re-check for vacuum.

if vacuum exists possible leaking intake gasket. (bottom of ports)

 

I did the tests and the vacuum still exists.

With the breather tube disconnected, the engine is "eating" a lot of vacuum for the breather hole at the valve cover.

Today, some overheating condition was presented at normal driving conditions. Sound like the head gasket? or could be the intake manifold gasket? Other possibilities?

Thanks for the replies.

 

its normal

 

Pull the breather and PCV out.
Plug the holes (on the valve covers) with your hands (cold eng preferably), if you feel a vacuum on your hands, the intake gasket is leaking, or possibly the intake is cracked underneath.
If you feel a strong vacuum, pull your hands off quick. If the vacuum builds up too much, it can unseat various oil seals and cause an oil leak.

 

Under normal conditions there's usually pressure inside the crankcase. At an idle it should be almost neutral.

There are very few places where it can be getting a vacuum source from. The most obvious is from the PCV since that's a vacuum source to vent excess pressure and vapours back into the combustion chambers. It's not really strong enough to be able to feel vacuum from the dipstick.

Since you've unplugged the PCV breather and there's still a vacuum in the crankcase, I'd also go with a cracked intake manifold underneath. There's a possibility is having a bad intake manifold gasket and it's sucking past the gasket from the crankcase. Since it's only leaking at the bottom of the gasket, you'll never find a leak looking across the top.

The reason it overheated is because the extra air being sucked into the combustion chamber has made a lean mixture. If you keep driving it you risk melting some parts.

Start by pulling the intake manifold off. If there isn't an obvious bad gasket, start looking for a cracked manifold.

Having a crankcase in a vacuum is good as long as it doesn't have more than 12 in/hg. Getting it the way your engine is doing it isn't the proper way. Using vacuum pumps is better, electric or mechanical. When the crankcase is in a vacuum, you can make more power and since there's no pressure in the crankcase, seals won't weep. The downside is that the rear main seal is designed to keep oil from being pushed out. Not keep air from coming in. Race engine that use vacuum pumps usually turn the real main around. If the crankcase goes into too much vacuum 16+ in/hg you can start pulling oil from the bearings and wrist pins and seize the engine.

 

O.K. Thanks for the replies.

I dissasembled 1/2 engine this last weekend (no a big deal, only 1 damaged finger - I bought gloves but I didn't use them - ).

The intake manifold gasket was bad, then the engine was running with a strange mixture: air/fuel/oil. The pistons, valves and heads have a lot of carbon.

I'll starts cleaning all.

 

cool! I was wondering what happened to this thread. It's nice to see an update on what was wrong.