Dear all,
a friend of mine has a Rover V8 that has started to develop a fault and we are trying to diagnose the cause.
The engine is a 1985 v8 with twin su carbs in a rover sd1. I don't know the mileage for sure, think it is about 150,000 ish.
When you start the engine from cold, it starts ok and settles down to a smooth idle. Oil pressure at idle (from the rover dash gauge) is 15 to 20 psi and then rises when throttle blipped.
However when the car has been left to idle for 15 to 20 mins the engine develops a knocking noise. See video below.
<iframe width="560" height="315" src="https://www.youtube.com/embed/zqkj3PqaPik" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
If you rev the engine up, the noise doesnt go away, just increase with engine speed. If you leave the engine to cool down for about 5 mins and re start it, the noise is gone, until it warms up again.
We drained about 1/2 pint oil from the sump and found no evidence of metallic particles.
To me it sounds like something in the top end. It doesnt sound like main or big ends. I thought it could be a lazy tappet, but i cant understand why it would only do it when hot. Id have thought it would be the other way round, and then pump up when revs were lifted and oil pressure increases.
It could also be a little end bearing or piston slap, so as its warmed up the tolerances increase and with warm thin oil you get enough slack in a bearing to cause the knock.?
Basically does anyone have an idea what it might be and how to diagnose further before the engine has to come out and get pulled apart.
I'm thinking oil flush, oil filter and oil change and try again.
Any help appreciated.
a friend of mine has a Rover V8 that has started to develop a fault and we are trying to diagnose the cause.
The engine is a 1985 v8 with twin su carbs in a rover sd1. I don't know the mileage for sure, think it is about 150,000 ish.
When you start the engine from cold, it starts ok and settles down to a smooth idle. Oil pressure at idle (from the rover dash gauge) is 15 to 20 psi and then rises when throttle blipped.
However when the car has been left to idle for 15 to 20 mins the engine develops a knocking noise. See video below.
<iframe width="560" height="315" src="https://www.youtube.com/embed/zqkj3PqaPik" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
If you rev the engine up, the noise doesnt go away, just increase with engine speed. If you leave the engine to cool down for about 5 mins and re start it, the noise is gone, until it warms up again.
We drained about 1/2 pint oil from the sump and found no evidence of metallic particles.
To me it sounds like something in the top end. It doesnt sound like main or big ends. I thought it could be a lazy tappet, but i cant understand why it would only do it when hot. Id have thought it would be the other way round, and then pump up when revs were lifted and oil pressure increases.
It could also be a little end bearing or piston slap, so as its warmed up the tolerances increase and with warm thin oil you get enough slack in a bearing to cause the knock.?
Basically does anyone have an idea what it might be and how to diagnose further before the engine has to come out and get pulled apart.
I'm thinking oil flush, oil filter and oil change and try again.
Any help appreciated.
