Diesel knock

Dent · Dec 10, 2009

200tdi was running fine, but now developed diesel knock on light or trailing throttle, was told it had a belt 20.000 mile ago, did wonder if the belt had gone slack, but not sure if this would advance or retard it.

Any thoughts ?

Bromsgrove Defender · Dec 10, 2009

Think I'd be worrying more about other potential probs than just a slack belt.

Could be piston slap.......
You dont say how many miles its done...

Has it got any oil in it????

Dent · Dec 10, 2009

lol, no it's a good engine, plenty of oil/pressure, 140k, it's deffo diesel knock and not piston slap, but I just wonded why it's developed it, been on 50/50 veg for about a month, can't see why that should do it though.

Bromsgrove Defender · Dec 10, 2009

Errr Colder weather??

robint · Dec 10, 2009

try a 75/25 mix see if that works

Dent · Dec 10, 2009

Bromsgrove Defender said:
Errr Colder weather??

robint said:
try a 75/25 mix see if that works

Maybe it is the colder weather, starts first time though, might just fill up with diesel

.

Bromsgrove Defender · Dec 10, 2009

Dent said:
Maybe it is the colder weather, starts first time though, might just fill up with diesel .

I think it'd be worth trying it, especially if that solves the prob.

If it doesn't at least you'll know that weren't it........

barmatt · Dec 10, 2009

50/50 is a bit much veg oil for the cold weather I'm afraid, I don't use more than 30/35% in the winter.

Bromsgrove Defender · Dec 10, 2009

barmatt said:
50/50 is a bit much veg oil for the cold weather I'm afraid, I don't use more than 30/35% in the winter.

Er that only adds up to 65% whats the other 35% then ????

barmatt · Dec 10, 2009

Bromsgrove Defender said:
Er that only adds up to 65% whats the other 35% then ????

I knew some fastidious git would say that

.

Ok I should have said "50% is to much veg oil for the winter" not 50/50.

Better? :mooning:

Bromsgrove Defender · Dec 10, 2009

barmatt said:
I knew some fastidious git would say that.

Ok I should have said "50% is to much veg oil for the winter" not 50/50.

Better? :mooning:

Nope that bit was fine it was the 30/35 that got me

barmatt · Dec 10, 2009

Bromsgrove Defender said:
Nope that bit was fine it was the 30/35 that got me

What you worried about TD5's don't like veg anyhoo

.

Bromsgrove Defender · Dec 10, 2009

barmatt said:
What you worried about TD5's don't like veg anyhoo.

Thought that were a wicked rumour?

CharlesY · Dec 10, 2009

Dent said:
lol, no it's a good engine, plenty of oil/pressure, 140k, it's deffo diesel knock and not piston slap, but I just wonded why it's developed it, been on 50/50 veg for about a month, can't see why that should do it though.

If it is a DIESEL engine, and it is on trailing throttle (i.e. foot OFF the throttle pedal and the car slowing down) any Knocking noise IS NOT and CAN NOT BE diesel knock.

End of discussion.

The knocking must be due to some other fault, probably mechanical wear, and classically piston slap or a failure of a small end bearing.

CharlesY

Dent · Dec 10, 2009

CharlesY said:
If it is a DIESEL engine, and it is on trailing throttle (i.e. foot OFF the throttle pedal and the car slowing down) any Knocking noise IS NOT and CAN NOT BE diesel knock.

End of discussion.

The knocking must be due to some other fault, probably mechanical wear, and classically piston slap or a failure of a small end bearing.

CharlesY

I call trailing throttle when you more or less balance it, ie.backed off BUT NOT fully, then throttle

It is diesel knock :doh: it's the cause that's the issue .

CharlesY · Dec 10, 2009

Dent said:
200tdi was running fine, but now developed diesel knock on light or trailing throttle, was told it had a belt 20.000 mile ago, did wonder if the belt had gone slack, but not sure if this would advance or retard it.

Any thoughts ?

If the belt slackens the timing RETARDS, but if it did that enough to make any difference, the belt would jump the pulleys and stuff the whole issue.

Dent said:
I call trailing throttle when you more or less balance it, ie.backed off BUT NOT fully, then throttle

It is diesel knock :doh: it's the cause that's the issue .

See what you said FIRST, which is utterly different from what you say SECOND.

In the first instance you are saying "TRAILING THROTTLE", but in the second you are saying "THEN THROTTLE" implying putting your foot down a bit on the GO pedal.

These are two completely opposite situations

If it is TRAILING THROTTLE then no, it is not diesel knock. It CAN NOT BE, and if you understood diesels you would know why.

If it is knocking when you apply throttle especially at low revs then there is one classic reason for that situation too.

But as you're the expert you don't need me to tell you what it is.

End of my input.

CharlesY

Dent · Dec 10, 2009

CharlesY said:
If the belt slackens the timing RETARDS, but if it did that enough to make any difference, the belt would jump the pulleys and stuff the whole issue.

See what you said FIRST, which is utterly different from what you say SECOND.

In the first instance you are saying "TRAILING THROTTLE", but in the second you are saying "THEN THROTTLE" implying putting your foot down a bit on the GO pedal.

These are two completely opposite situations

If it is TRAILING THROTTLE then no, it is not diesel knock. It CAN NOT BE, and if you understood diesels you would know why.

If it is knocking when you apply throttle especially at low revs then there is one classic reason for that situation too.

But as you're the expert you don't need me to tell you what it is.

End of my input.

CharlesY

OOOOOOOOOOOoooooooooo

CharlesY · Dec 10, 2009

Dent said:
OOOOOOOOOOOoooooooooo

Well, was he THROTTLE OFF as in Trailing Throttle or THROTTLE ON as in pulling away from low revs?

There's a friggin' difference!

Geez, but how is anyone supposed to offer advice if the descriptions of the symptoms are arse over tit?

CharlesY

GRATCH · Dec 10, 2009

does the vacuum pump knock when it's on its way out?

CharlesY · Dec 10, 2009

GRATCH said:
does the vacuum pump knock when it's on its way out?

Yes, but it would not be sensitive to throttle position.

His engine probably IS diesel knocking when (BECAUSE) he applies throttle.

It is easily cured.

If it is NOT cured fairly smartish, it will knock seven bells out his pistons, rings, big-ends and head gasket.

CharlesY

Diesel knock

New Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

New Member

Well-Known Member

New Member

Well-Known Member

HUGE MEMBER

Well-Known Member

Similar threads