dubmikeP38
New Member
- Posts
- 2
Hi all,
I#m new around here so firstly thank you for looking at this problem at all, and mega thank you's to anyone who can help me to clear up the diagnosis.
here goes.....
I have a very well looked after P38 4.6 Bosch that I really need a 2nd opinion on. 230,000 kms and serviced all the way, still has a light brown tarnish inside with no gunking.
It has a very loud Valve 'Slap' sound that has developed from a 'tick'. It doesn't have it unless under load, even light load held in gear and it's there. Nothing while ticking over or when revved unless you really dig it. Engine under light load revved to 4-5,000 rpm is sewing machine smooth, no noise.
This 'slap' is loud enough to make you feel like it's about to throw a rod! It gets attention from everyone and is basically undriveable.
I've diagnosed the cylinder the problem is on, when the plug lead is connected to a 9th plug earthed off on the intake, the noise is completely gone. The car runs great, on the remaining 7 cylinders with the faintest noise. (btw the bad cylinder is the 2nd from your leg if in a RHD, though mine's a LHD)
This rules out the cat, as the cat on that side was a little rattly I had incorrectly diagnosed the slight rattly ticking problem from the outset as a piece of cat material doing circles around the housing. Unfortunately, at that point I kept on driving.
From the outside of the car it sounds like the slap is coming from the exhaust, but not when you're listening from under the bonnet.
So I've stripped all the annoying stuff off the top and pulled the rocker cover, all I can ascertain at this point when turning over the motor (not starting) is that when the offending cylinder is on the compression stroke, there is a noticeable "Phsssht!" Air being expelled. But where?
I'm hovering between leaking head gasket (cylinder to cylinder as there's not pressuring of water or contamination of oil) and a sticking valve.
The valves appear to be hitting the spot to the naked eye, but perhaps not. Or a very slight overheat a few months ago may have done the trick, water consumption may be up a touch?
Can anyone give some opinions on this and help me decide the diagnosis or correct me if I'm out on both of them? If it's the valve, is there any way to release it without pulling the heads and doing a full top end rebuild?
Any and all opinions very gratefully received, my mountain transport is down to a Suzuki Santana SJ410, nice little backup machine but not a Rangie!
Best regards,
Mike
I#m new around here so firstly thank you for looking at this problem at all, and mega thank you's to anyone who can help me to clear up the diagnosis.
here goes.....
I have a very well looked after P38 4.6 Bosch that I really need a 2nd opinion on. 230,000 kms and serviced all the way, still has a light brown tarnish inside with no gunking.
It has a very loud Valve 'Slap' sound that has developed from a 'tick'. It doesn't have it unless under load, even light load held in gear and it's there. Nothing while ticking over or when revved unless you really dig it. Engine under light load revved to 4-5,000 rpm is sewing machine smooth, no noise.
This 'slap' is loud enough to make you feel like it's about to throw a rod! It gets attention from everyone and is basically undriveable.
I've diagnosed the cylinder the problem is on, when the plug lead is connected to a 9th plug earthed off on the intake, the noise is completely gone. The car runs great, on the remaining 7 cylinders with the faintest noise. (btw the bad cylinder is the 2nd from your leg if in a RHD, though mine's a LHD)
This rules out the cat, as the cat on that side was a little rattly I had incorrectly diagnosed the slight rattly ticking problem from the outset as a piece of cat material doing circles around the housing. Unfortunately, at that point I kept on driving.
From the outside of the car it sounds like the slap is coming from the exhaust, but not when you're listening from under the bonnet.
So I've stripped all the annoying stuff off the top and pulled the rocker cover, all I can ascertain at this point when turning over the motor (not starting) is that when the offending cylinder is on the compression stroke, there is a noticeable "Phsssht!" Air being expelled. But where?
I'm hovering between leaking head gasket (cylinder to cylinder as there's not pressuring of water or contamination of oil) and a sticking valve.
The valves appear to be hitting the spot to the naked eye, but perhaps not. Or a very slight overheat a few months ago may have done the trick, water consumption may be up a touch?
Can anyone give some opinions on this and help me decide the diagnosis or correct me if I'm out on both of them? If it's the valve, is there any way to release it without pulling the heads and doing a full top end rebuild?
Any and all opinions very gratefully received, my mountain transport is down to a Suzuki Santana SJ410, nice little backup machine but not a Rangie!
Best regards,
Mike
