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[Ewan]

Hi. Can anyone explain to me why this particular engine is blighted with the problem of leaking cam cover gaskets? I've had many cars over the years and none of them did this. It must have become apparent to Vauxhall fairly soon that there was a problem, so why could they not have altered the design. One of the smaller tubes going into the breather box on top of the plenum seems incredibly restricted when trying to suck or blow through it. I can't imagine what it does.

[Kevin Wood]

It's restricted to control the amount of air that bleeds through the crankcase into the intake manifold. You need just enough flow to keep the crankcase in a slight negative pressure and purge it of any blowby gases without introducing such a large air leak into the intake that it affects engine running.

The main reason the system blocks is that the oil change interval is too long, IMHO. Change the oil every 5-6k (not 10k or even 20k on later cars) and the breathers stay clear and the cam cover gaskets last reasonably well.

[Ewan]

Thanks for the reply, but why should other cars be able to run for much longer without needing an oil change, and indeed I've had some that thrived on neglect. I have particularly fond memories of the old Rover V8. So simple and easy to repair.

[Osprey]

Call me a bitter, crusty, twisted old cynic but I don't think other cars can run for much longer without needing an oil change.  Like the Omega, they can survive their scheduled 60K design life with unrealistically long oil change intervals but, also like the Omega, they would run sweeter, cost less to maintain and last several times longer on a 5K oil chance regime.  IMHO.

[v6man54deg Geffd]

The oil leaks on the V6 engine are mainly due to high oil pressure, the system should be regulated to 5 bar max - this is regulated by a spool valve in the oil pump - when the oil pressure gets to 5 bar it pushes the spool valve down so the oil  is then pumped back to the pump when the pressure drops the spool valve returns and oil is pumped back the the engine - the problem is the oil feed which is approx 2mm diameter and is in the oil path that feeds No 1 main and then down to the oil pressure switch - this gets clogged up so oil can't get to the spool valve - the v6 oil pump is capable of upto 10 bar - then a relief valve dumps it into the crankcase - i found this on many V6 engines during my time at the plant testing v6 engines for durability / warranty claims.
this can be tested using an oil pressure gauge in place of the oil pressure switch - if over 5 bar (very common to see 7- 8 bar) a good engine flush can clear the oil feed and return normal oil pressure.

[Abiton]

Hi. Can anyone explain to me why this particular engine is blighted with the problem of leaking cam cover gaskets? I've had many cars over the years and none of them did this. It must have become apparent to Vauxhall fairly soon that there was a problem, so why could they not have altered the design. One of the smaller tubes going into the breather box on top of the plenum seems incredibly restricted when trying to suck or blow through it. I can't imagine what it does.

Aside from what has just been said above, because the camcovers are made of plastic. Different rate of thermal expansion to that which it is attached to, very flexible when hot, etc...

Edit: regarding the over-pressure situation referred to above, how does that relate to the camcover gaskets though, these gaskets aren't in the high-pressure system?  :-/

[Marks DTM Calib]

Thanks for the reply, but why should other cars be able to run for much longer without needing an oil change, and indeed I've had some that thrived on neglect. I have particularly fond memories of the old Rover V8. So simple and easy to repair.

Lol, I am yet to find a Rover V8 which has more than 60K miles on it that is running on 8 cylinders.

Every one has a stretched timing chain and worn cam plus followers with all but the very last few years of production suffering head gasket leaks toward the valley.

The only reason why it goes unnoticed is because you barely notice it on a V8!

As for breather system, the V8 was very bad for that as the oil would be pretty goosed by 3K miles and you see them full of tar. On these, the flame trap on the rear of bank 1 clogs and then the crank seals blow out.

[Marks DTM Calib]

Hi. Can anyone explain to me why this particular engine is blighted with the problem of leaking cam cover gaskets? I've had many cars over the years and none of them did this. It must have become apparent to Vauxhall fairly soon that there was a problem, so why could they not have altered the design. One of the smaller tubes going into the breather box on top of the plenum seems incredibly restricted when trying to suck or blow through it. I can't imagine what it does.

Aside from what has just been said above, because the camcovers are made of plastic. Different rate of thermal expansion to that which it is attached to, very flexible when hot, etc...

Edit: regarding the over-pressure situation referred to above, how does that relate to the camcover gaskets though, these gaskets aren't in the high-pressure system?  :-/

It wont affect the breather system 

As for the cam covers, I also disagree.

I must have worked on 100+ Omega V6's and had one myself with 190K+ miles on the clock and pretty much every one ahs the original covers.

I can accept the fact that over time the rubber goes hard (I suspect they may need changing once in the average life of the car, twice on longer lived one).

THE main failure cause is blocked breathers due to old oil.

And on those engines which dont have a weak point like the camcover gaskets, they take out the crank seal (as per many a V6 Vectra I ahve sadly repaired....particularly when its the gearbox end!) 

[foggy]

i mate my v6 waz pressurerisin threw the dipstick and oil filler cap so i blow breather pipes out with airline and it stopped it flushed engine out new oil changed gasket and it is fine

[v6man54deg Geffd]

If you have nearly twice as much pressure than is intended in the oil system - it then builds up the pressure in the crankcase - you also have four T vents in the cylinder head

[Marks DTM Calib]

If you have nearly twice as much pressure than is intended in the oil system - it then builds up the pressure in the crankcase - you also have four T vents in the cylinder head

Sorry Geff, still not convinced.

If the oil pump is creating higher pressure in the oil ways then its creating a consequental lower pressure in the crank case (as its effectively a sealed system).

In can see how this could cause an oil pump gasket failure. 

The breathers are more than man enough to drag the crank case pressure down (as the inlet ducts will have a very slight vaccum pulling on the larger breathers due to the minor restriction of the inlet and air filter)

[v6man54deg Geffd]

on every v6 i work on that has major oil leaks I firstly check the oil pressure!

yes its common for the small breather (idle speed) from the vent housing to clog up - but if the large breather is blocked its time to look at the piston rings as blow by must be through the roof!

[Ewan]

Excellent info - thanks very much. Don't get me wrong, I think the V6 is a lovely engine, it's just that there's so much of it to take apart, and not all of it very accessible. I must have been lucky then with my V8s. I put one in a home made car with plenty of access all round and it was a delight. With a TR6 exhaust it sounded absolutely superb, and returned around 28mpg.