Omega 2.2 petrol 2003 excessive pressure when oil filler cap removed at idle

[Marks DTM Calib]

Head gasket failing won't pressurise the crank case. Could you explain what will?

Is the cam timing OK? Checked the timing this morning and all is still aligned correctly.

Oil consumption up? No. It hasn't used any oil at all.

The key thing that will pressurise the crank case is blow by gases, head gasket is very very very very unlikely to as the section around the fire rings is a coolant jacket hence you would see coolant loss and a very heavily pressurised cooling system.

There is no PCV valve, what I have seen though is crud in the top of the cam cover blocking the PCV ports.

Also be aware, is the hiss when you remove the oil filler gas escaping or air being sucked in as the crank case will run at a slight vaccum under normal operating conditions.

If you remove the large breather from the pre throttle connection and then blank the port it connected to on the inlet, run the engine do you get much flow from the breather tube?

[TheBoy]

It should raise a code... P0115 iirc

Only if frecked. Not if lazy or covered in k-seal etc

[05omegav6]

It should raise a code... P0115 iirc

Only if frecked. Not if lazy or covered in k-seal etc

Ok, so only conclusive test is Tech 2 reading compared to gauge reading

[TheBoy]

It should raise a code... P0115 iirc

Only if frecked. Not if lazy or covered in k-seal etc

Ok, so only conclusive test is Tech 2 reading compared to gauge reading

Live data is only true way.  And comparing it with the Live data of the instrument panel, as the needle reading is, errr, "frigged".

[05omegav6]

Gotcha

[terry paget]

I'd be checking the breathers again.

Thanks for replying.

I took the three breather pipes off the cam cover and they are clean.

With the engine running I put my thumb over the small pipe from the cam cover that goes to the throttle body and that is sucking air nicely. So the hole in the throttle body is clear.

With the engine running I stuck a thumb over the large hole on the can cover where the breather pipe came off and there was plenty of air coming out of the small hole. I then blocked the small hole and there was plenty of air coming out from the large hole. So no blockage in the cam cover itself.

Is there any other pipes or valves that I need to check?

How much positive pressure should I have coming from the crankcase?

Thanks

The crankcase should always be under suction, so that noxious crankcase gases are sucked into the engine and burned. You say the cam cover is pressurised at idle, that is when the small hole taking high vacuum between throttle and engine provides suction. At high throttle openings there is little vacuum remaining at this point, so suction is taken between throttle and air filter through the large hose. You say you have checked the small pipe for suction at idle. You do not seem to have checked suction in the large pipe.
I have not got a 2.2 here, only a 2.0. That is very prone to blockage by oil of the small hole, which does the job at idle. This can be cleared by poking a wire through it. It may be your small hole is partially blocked, so that the suction is not sufficent to match pressure from blow past. That would result in pressurisation of cam cover at idle.

[Andy A]

Head gasket failing won't pressurise the crank case. Could you explain what will?

Is the cam timing OK? Checked the timing this morning and all is still aligned correctly.

Oil consumption up? No. It hasn't used any oil at all.

The key thing that will pressurise the crank case is blow by gases, head gasket is very very very very unlikely to as the section around the fire rings is a coolant jacket hence you would see coolant loss and a very heavily pressurised cooling system.

There is no PCV valve, what I have seen though is crud in the top of the cam cover blocking the PCV ports.

Also be aware, is the hiss when you remove the oil filler gas escaping or air being sucked in as the crank case will run at a slight vaccum under normal operating conditions. When I take the filler cap off I get a lot of positive air pressure escaping and no vaccum.

If you remove the large breather from the pre throttle connection and then blank the port it connected to on the inlet, run the engine do you get much flow from the breather tube? Yes, enough to feel the air pressure from 4-5 inches away from the end of the tube.

[Andy A]

I'd be checking the breathers again.

Thanks for replying.

I took the three breather pipes off the cam cover and they are clean.

With the engine running I put my thumb over the small pipe from the cam cover that goes to the throttle body and that is sucking air nicely. So the hole in the throttle body is clear.

With the engine running I stuck a thumb over the large hole on the can cover where the breather pipe came off and there was plenty of air coming out of the small hole. I then blocked the small hole and there was plenty of air coming out from the large hole. So no blockage in the cam cover itself.

Is there any other pipes or valves that I need to check?

How much positive pressure should I have coming from the crankcase?

Thanks

The crankcase should always be under suction, so that noxious crankcase gases are sucked into the engine and burned. You say the cam cover is pressurised at idle, that is when the small hole taking high vacuum between throttle and engine provides suction. At high throttle openings there is little vacuum remaining at this point, so suction is taken between throttle and air filter through the large hose. You say you have checked the small pipe for suction at idle. You do not seem to have checked suction in the large pipe.
I have not got a 2.2 here, only a 2.0. That is very prone to blockage by oil of the small hole, which does the job at idle. This can be cleared by poking a wire through it. It may be your small hole is partially blocked, so that the suction is not sufficent to match pressure from blow past. That would result in pressurisation of cam cover at idle.

I'll take the throttle body off and give it a good clean and see if that's the problem. Maybe its part blocked like you said.

If not, I will buy a true 100psi leak down tester. Do you know of any good compressors on the market for around £100 that will run at 100psi and will be good enough for some air tools for the car?

[Andy A]

Found the problem at last.

The small new rubber hose that goes to the throttle body was at fault. Although brand new and fitted less than a year ago had air line cracks in it on closer inspection. I took it back and got it replaced. They said it was probably old stock. 

Fitted the new one and although I still get a lot of positive pressure coming from the oil filler cap opening when the cap is off. When the cap is fitted I now get a negative pressure (suction) through the large breather pipe that comes from the cam cover and connects to the air filter pipe, when the engine is idling (I did not have this before it was positive pressure). So the crankcase when sealed, is now under negative pressure at last as it should be.

Thanks all, for all your help.