V8 valley gasket
Discussion
i used hermatite red for both sides of the gasket and green for the end seals, thats after cleaning the surfaces, left it over night and had a 2 mile run and it had already started leaking, this is the third time i have done it, previously i used a composite gasket, and this time i used a tin one, what worrys me is the way its bending upwards, with either heat or air pressure.
the little breather on top of the right bank seemed blocked, i have cleared it now, however when i remove the breather hose from the left bank that goes into the plenum chamber its kicking out loads of hot steam and you can visibly see the valley gasket moving also when the hose is refitted, the engine revs go down.
i suspect head gasket failure.
it seems to be running hot as temp gauge goes right over within a minute or so, no water overflowing though but engine seems really overly hot, not sure if gauge is right.
what do you think
thanks for you help.
henry.
i suspect head gasket failure.
it seems to be running hot as temp gauge goes right over within a minute or so, no water overflowing though but engine seems really overly hot, not sure if gauge is right.
what do you think
thanks for you help.
henry.
bin looney said:
the little breather on top of the right bank seemed blocked, i have cleared it now, however when i remove the breather hose from the left bank that goes into the plenum chamber its kicking out loads of hot steam and you can visibly see the valley gasket moving also when the hose is refitted, the engine revs go down.
i suspect head gasket failure.
it seems to be running hot as temp gauge goes right over within a minute or so, no water overflowing though but engine seems really overly hot, not sure if gauge is right.
what do you think
thanks for you help.
henry.
i suspect head gasket failure.
it seems to be running hot as temp gauge goes right over within a minute or so, no water overflowing though but engine seems really overly hot, not sure if gauge is right.
what do you think
thanks for you help.
henry.
When you disconnect the breather, make sure you blank off the end that goes to the throttle/intake otherwise you'll get unmetered air in there. This *might* be why the revs go up when you disconnect and down when you connect.
Steam out of the breather is also normal - most of the breather gases are similar to the stuff that comes out of the exhaust and have quite a high water content.
What you need to do now is find out whether the breather gases are coming out at roughly the normal rate and whether any of the cylinders are blowing into the water jacket, oil way or crank case. Do you have a pressure tester or leakdown tester? You can get a very rough idea of the breather flow rate by sticking a bag over the breather and seeig how much you collect. As a very rough guide you should expect to get a few liters a minute at tickover. If you get masses more than this then that's a bad sign.
bin looney said:
when you say bad sigh what do you mean.
A really massive amount of breather gases would suggest that one or more cylinders is blowing into the crank case, which could be via the pushrod holes if the HG has one (although probably not the most common symptom of HG failure), or worn/scored bores/broken rings, or possibly something more catastrophic like a damaged piston. But don't frighten yourself too much until you know how much is really coming out of the breather. If the breather was totally blocked then the crank case would build up more and more pressure until something let go - so that might be the only problem you have.
To check for scored bores or broken rings you need a compression test.
Borrow or buy a pressure gauge.
Warm the engine up then remove all the plugs.
Disconnect the injectors (and cold-start injector) so they don't put petrol in the bores.
Wedge the throttle fully open.
Run the compression test on each cylinder by cranking the engine over on the starter.
Using an oil-can squirt a fair amount of oil into each cylinder - try to get it all around the top of the piston.
Run the compression test again.
The compression of all cylinders should be fairly even (within 10-20% of each other). They should be 120 psi (less for a very worn motor).
If one is very low measured dry and better with the oil in then this is a sign of scored bores or a cracked ring because the oil makes a better seal.
If it doesn't improve with the oil then it is likely to be the valves at fault.
To run the tests described elsewhere on crankcase pressure, forget the bleeder, take the oil filler cap off and tape a surgical glove over the hole, you should see it expand, if it pops too soon then start to worry.
There are two ways for the crankcase pressure to bleed out, one is the breather on the rocker cover top, this should have a filter on it for when the crankcase is at negative pressure, the other is a bleed into the throttle area which actually sucks air and oil fumes into the cylinders to burn. On a new tight engine there may be a partial vacuum in the crankcase; if you then open this up to the air then extra air will be sucked in so the revs will rise.
Russ
Borrow or buy a pressure gauge.
Warm the engine up then remove all the plugs.
Disconnect the injectors (and cold-start injector) so they don't put petrol in the bores.
Wedge the throttle fully open.
Run the compression test on each cylinder by cranking the engine over on the starter.
Using an oil-can squirt a fair amount of oil into each cylinder - try to get it all around the top of the piston.
Run the compression test again.
The compression of all cylinders should be fairly even (within 10-20% of each other). They should be 120 psi (less for a very worn motor).
If one is very low measured dry and better with the oil in then this is a sign of scored bores or a cracked ring because the oil makes a better seal.
If it doesn't improve with the oil then it is likely to be the valves at fault.
To run the tests described elsewhere on crankcase pressure, forget the bleeder, take the oil filler cap off and tape a surgical glove over the hole, you should see it expand, if it pops too soon then start to worry.
There are two ways for the crankcase pressure to bleed out, one is the breather on the rocker cover top, this should have a filter on it for when the crankcase is at negative pressure, the other is a bleed into the throttle area which actually sucks air and oil fumes into the cylinders to burn. On a new tight engine there may be a partial vacuum in the crankcase; if you then open this up to the air then extra air will be sucked in so the revs will rise.
Russ
NO TEARS.
EACH BORE SHOWED 140 PSI.
WHERE BREATHER HOSE CONNECTS TO PLENUM SEEMED SLIGHTLY BLOCKED, I PISHED A BIT OF WIRE IN AND IT WAS COVER IN BLACK SLUDGE. SO I BLASTED IT OUT WITH COMPRESSED AIR.
HOWEVER THERE IS A LOT OF STEAM BEING PUMPED FROM THE BREATHER HOSE AND SHOOTS OUT WHEN ITS REVVED, ALSO THERE IS A LOT COME OUT OF OIL FILLER WHEN CAP IS REMOVED PLUS ITS GOT A LAYER OF SLUGE APPEARING.
GOING TO FIT SOME HEAD GASKETS FOR WHAT THEY COST, JUST A BIT OF TIME AND LOST KNUCKLE SKIN THATS ALL!.
COULD THE HEAD GASKETS BE CAUSING THE ENGINE TO OVERHEAT ASWELL?
EACH BORE SHOWED 140 PSI.
WHERE BREATHER HOSE CONNECTS TO PLENUM SEEMED SLIGHTLY BLOCKED, I PISHED A BIT OF WIRE IN AND IT WAS COVER IN BLACK SLUDGE. SO I BLASTED IT OUT WITH COMPRESSED AIR.
HOWEVER THERE IS A LOT OF STEAM BEING PUMPED FROM THE BREATHER HOSE AND SHOOTS OUT WHEN ITS REVVED, ALSO THERE IS A LOT COME OUT OF OIL FILLER WHEN CAP IS REMOVED PLUS ITS GOT A LAYER OF SLUGE APPEARING.
GOING TO FIT SOME HEAD GASKETS FOR WHAT THEY COST, JUST A BIT OF TIME AND LOST KNUCKLE SKIN THATS ALL!.
COULD THE HEAD GASKETS BE CAUSING THE ENGINE TO OVERHEAT ASWELL?
Well a bunch of steam a bit like a lightly boiling kettle isn't unusual. Does the engine eject any coolant? if not I wouldn't bother with the head gaskets.
Did you check the passageway into the plenum? If the hose was blocked, this can get gunged up too. Very hard to clean, though. I have done it by blowing some cotton through. To the cotton I attach a thread, and to the thread a string, then some thick string. On the thick string you can tie a rag. If you get it right you can pull the rag back and forth through the air passage to scrape out the gunge, with the help of some petrol.
Did you check the passageway into the plenum? If the hose was blocked, this can get gunged up too. Very hard to clean, though. I have done it by blowing some cotton through. To the cotton I attach a thread, and to the thread a string, then some thick string. On the thick string you can tie a rag. If you get it right you can pull the rag back and forth through the air passage to scrape out the gunge, with the help of some petrol.
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