Disco 1 compression issue

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Armandbey

New Member
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8
Location
South Africa
Hi.I need some help please.I have a Disco 1 V8 3.9L.My problem is that it is blowing a lot of air out of the oil filler cap.The engine is also running very uneven and it does not have any power.It starts and idle fine.Someone told me that it could be sump compression but the motor was redone about a year ago.Also it is not smoking and starts easy from cold.Any idea what else besides rings that can cause this issue.Sounds and feels like it is not running on all cylinders.
Thanks
Armand
 
OOPS! Sounds like worn piston/compression rings allowing pressure to bypass the pistons and down into the sump as your mate said. But it could also be a blocked crankcase breather, ditto rockershaft breather, if you have one, or two in your case.
Hope it is not the first one. If when the engine was "redone" was it properly run in? Also I believe there may be an issue with a liner, or liners that might have slipped.
Just wondering if this could also be a system of a gasket malfunction.
 
Stanleysteamer said:
OOPS! Sounds like worn piston/compression rings allowing pressure to bypass the pistons and down into the sump as your mate said. But it could also be a blocked crankcase breather, ditto rockershaft breather, if you have one, or two in your case.
Hope it is not the first one. If when the engine was "redone" was it properly run in? Also I believe there may be an issue with a liner, or liners that might have slipped.
Just wondering if this could also be a system of a gasket malfunction.
Click to expand...

Hi Stanley
Thanks for the response.That is why I can't figure it out.There is no oil in the water.The car is not smoking or using any oil.It is just down on power and breathing heavily through the oil filler hole.Do you think a dead plug could cause this as it is definitely not running on all cylinders.I'm just wondering if a dead plug could cause so much cranc case vapours?
 
Armandbey said:
Hi Stanley
Thanks for the response.That is why I can't figure it out.There is no oil in the water.The car is not smoking or using any oil.It is just down on power and breathing heavily through the oil filler hole.Do you think a dead plug could cause this as it is definitely not running on all cylinders.I'm just wondering if a dead plug could cause so much cranc case vapours?
Click to expand...
Sounds like you have possibly two issues here, lack of compression and misfiring.
Cannot see how a dead plug could cause lack of compression, no connection to crankcase.
But I'd start with a compression test on all cylinders. Don't forget to do the oil test to see if lack of compression is down to leaking piston rings or leaking valves.
To find a dead plug, get it running and short them out, or disconnect them, with insulated pliers! one by one, if there is a dead plug it'll show by being the one that DOESN't make the running worse, although always harder to tell with a V8.
Not running properly on all or any cylinders can be caused by a lack of spark, a lack of fuel to the cylinder, or it not holding compression due to a valve fault or a ring fault. Or Oiling up so badly that the plug cannot fire properly.
Pull all the plugs and compare them, if they are all the same colour that narrows it down a bit.
Check all rocker clearances to see if there is an issue with a lifter, could be a worn cam lobe which V8s are prone to. To see that use a Dial Test Indicator to see if all push rods are lifting as much as they should.
Check to see all inlet manifolds are tight to the head and not leaking. With the engine running, spray with EasyStart or somesuch. If the engine perks up, you've got a leak.
Have a go at this then get back to us. Don't forget, lack of water in the oil or oil in the water does not necessarily mean you do not have a gasket problem. There could be a break between cylinders that touches neither oilway nor waterway.
 
Stanleysteamer said:
Sounds like you have possibly two issues here, lack of compression and misfiring.
Cannot see how a dead plug could cause lack of compression, no connection to crankcase.
But I'd start with a compression test on all cylinders. Don't forget to do the oil test to see if lack of compression is down to leaking piston rings or leaking valves.
To find a dead plug, get it running and short them out, or disconnect them, with insulated pliers! one by one, if there is a dead plug it'll show by being the one that DOESN't make the running worse, although always harder to tell with a V8.
Not running properly on all or any cylinders can be caused by a lack of spark, a lack of fuel to the cylinder, or it not holding compression due to a valve fault or a ring fault. Or Oiling up so badly that the plug cannot fire properly.
Pull all the plugs and compare them, if they are all the same colour that narrows it down a bit.
Check all rocker clearances to see if there is an issue with a lifter, could be a worn cam lobe which V8s are prone to. To see that use a Dial Test Indicator to see if all push rods are lifting as much as they should.
Check to see all inlet manifolds are tight to the head and not leaking. With the engine running, spray with EasyStart or somesuch. If the engine perks up, you've got a leak.
Have a go at this then get back to us. Don't forget, lack of water in the oil or oil in the water does not necessarily mean you do not have a gasket problem. There could be a break between cylinders that touches neither oilway nor waterway.
Click to expand...

Thanks.I will do this and see if I can see where the issue is.Thanks for the help.
 
As above exactly worn rings or bores, if your having air/ smoke/oil fumes the from the engine oil filler and it’s excessive, of course there will also be blue smoke from the exhaust tail pipe, replacing rings only is a wast of time, engines can run ok with worn rings and without any issues other than blue smoke.

With the cap removed the crankcase breather on the offside rocker cover serves no purpose as the engine is now venting via the open oil filler.
Firstly all things being equal, any ‘normal fumes’ will be removed via the breather into the plenum chamber and burnt with the fuel, so unscrew the the flame trap and remove along with and clean both with petrol which should remove any carbon, if doesn’t then purchase a new flame trap, so what was the work involve “ redone” ?

Running issues could be something else, simple as an iffy air filter, spark plugs plug or leads, so checking and replacement is simple, but I suspect that was done with the work involve in “ redone” if running okay cold but then when up running temp there’s a misfire the the EFI coolant temp sensor may be faulty, but test don’t guess.
 
As above, I didn't want to get into any misfire issues caused by fuelling other than what I said, but if everything else is a normal then it would be time to look at all circuits to do with injectors, injectors themselves and ECU stuff, which is beyond my ken although RAVE will probably tell you tests you can run.
As @discool says, test don't guess.
 
Thanks Discool
With redone I mean the engine was completely redone.Rings,bearings.heads sent for engineering,so everything was redone.What I can't figure out is that if it was rings,shouldn't the car smoke a lot and use oil.It is not doing either of those.Looks like I will just have to start checking all the tests mentioned one by one.
 
I see that the previous owner drilled a hole in the oil filler cap.So this might have been a issue before.Did not have any problems before and I've had the car for about 10 years now.
 
Just doing rings is not "completely redone" unless the bores were not worn at all thus needing no rebore and new pistons. If bearings were replaced was the crank checked for ovality?
Completely redone to me is new pistons, rebore, crank reground, new camshaft bearings, possibly new cam, valve guides all checked and replaced if nec, valve seats refaced, new valves or valves at least reground and lapped in. etc, etc.
If you have had it for 10 years and it is only just showing problems then i doubt your problem is directly related to what happened before you got the truck. But it is interesting that the oil filler cap was drilled. That is really sticking an Elastoplast over the problem!
 
Armandbey said:
Thanks Discool
With redone I mean the engine was completely redone.Rings,bearings.heads sent for engineering,so everything was redone.What I can't figure out is that if it was rings,shouldn't the car smoke a lot and use oil.It is not doing either of those.Looks like I will just have to start checking all the tests mentioned one by one.
Click to expand...
Ok there will be a bedding period (running-in) but things should be back like a new engine but the bore could be worn.
Many years ago I replace the rings on a four cylinder engine over a weekend, and it was great afterwards but then after around 1000 miles the symptoms slowly returned, after 2000 miles (around five months) it was as bad as before, hence my comment that replacing rings is a wast of time.
I then went and got a recon/ rebored engine fitted, in a car with only 19000 miles on the clock, that’s Ford engines of the past for you.
 
compression test.

if it is blowing past the rings and has lost compression that'll cause a missfire and a lack of grunt.

When doing the test you are looking for an even reading more than 10% discrepancy is bad.

to prove/disprove a cylinder/piston problem remove the crank case ventilation system and run it, if it pumps excessive air/pressure with no messing around then you have a rings/piston issue.
 
Armandbey said:
I see that the previous owner drilled a hole in the oil filler cap.So this might have been a issue before.Did not have any problems before and I've had the car for about 10 years now.
Click to expand...
Strange as there is a small air intake at the top and at rear of that rocker cover, from which a small bore rubber pipe runs the the air filter box, therefore allowing filtered air inside the engine, well there was when the vehicle the factory:)
 
discool said:
Strange as there is a small air intake at the top and at rear of that rocker cover, from which a small bore rubber pipe runs the the air filter box, therefore allowing filtered air inside the engine, well there was when the vehicle the factory:)
Click to expand...
Some of this really isn't making sense.
 
OP said it was a 3.9 in his first post. I get the impression the previous owner had this problem and instead of getting to the bottom of it simply drilled a hole in the filler gap to let the pressure out! Bet there is a lovely oil stain on the bonnet inner lining just over the hole!
 
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