Engine knock when cold.

[RonnieM]

Hi all I am new to this forum, and I have a van with a DW8 engine in it, well its actually my wife's, the problem we have is that it knocks under acceleration when the engine is cold, it starts ok, a bit lumpy for a bit but that's what I would expect.
The engine has covered 120,000 miles and runs fine once warm (after about a mile) oil and water where it should be no mixing,
I am pretty sure that the knocking is caused by a misfire so I have changed the injectors but its still the same, so I am thinking head gasket, dose anyone have any other ideas before I embark on a head gasket change.

Thanks,
Ronnie.

[homeruk]

Doubt its the head gasket you would notice oil/coolant mixing and a loss of power.

A compression test wouldn't go amiss though

What does the temp gauge do until warm?

Any white smoke when you start? The lumpy start could be faulty glow plugs or relay.

[RonnieM]

Temp gauge works as I would expect, the van is ok once warmed up no power loss, when its knocking and misfiring then obviously there is power loss but if you change down and get the revs up then it clears, I was going to look at the EGR and make sure its not gunged up, I want to try every thing before I go and do a head gasket as that could be expensive between getting the head skimmed and bolts and gasket set.

[homeruk]

Its not the head gasket.

Egr was my next guess if its stuck partial open it would give you your symptoms including a lumpy start.

Always start simple and cheap

Have you done a timing belt change recently?

[RonnieM]

Its not the head gasket.

Egr was my next guess if its stuck partial open it would give you your symptoms including a lumpy start.

Always start simple and cheap

Have you done a timing belt change recently?

---

I cleaned the EGR valve, this made no difference, still have the machine gunner in the engine, this only happens when the engine is properly cold, if it was petrol it sounds like extreme pinking or even a big end, its not a big end or it would not go when the engine got hot, I have not changed the timing belt recently so its not the problem. Its a pre ECU model so it can't be sensors, I might just put up with it until it gets worse because once you drive about half a mile its ok and drives fine.

[geoff]

I'd also be thinking glow plugs.
Fuel filter and air filter new or old ?
Were the injectors new or second hand ? If s/h run a good slug of fuel cleaner in the tank
Next I'd be looking at valve clearances - easy to check but a camshaft out job to rectify ( not hard though ).
If checking the glow plugs then check the valve clearances at the same time as it make the engine easy to turn over to accurately.

[brodfather11]

If you have the 1.9 engine with mechanical pump timing then check the pump timing. Slightly out will cause problems.
The pump timing being out can cause knocking as well as overfueling
If you have the engine with electronic control of the pump check the crankshaft sensor is not loose

If you have the 2.0 litre engine then the tappets are hydraulic and don't need adjusting.

[homeruk]

Using a thinner oil can help too as can fully synthetic.

Sometimes knocking is caused by oil not circulating quick enough to parts which is why the knocking goes away when the engine is warm.

[brodfather11]

Quote "Sometimes knocking is caused by oil not circulating quick enough to parts which is why the knocking goes away when the engine is warm."

Unfortunately if the oil is not circulating fast enough when cold then the engine would not have lasted this long.

If no lubrication when hot or cold = Engine knackered.

[homeruk]

Quote "Sometimes knocking is caused by oil not circulating quick enough to parts which is why the knocking goes away when the engine is warm."

Unfortunately if the oil is not circulating fast enough when cold then the engine would not have lasted this long.

If no lubrication when hot or cold = Engine knackered.

Yes but when did the knocking start?

I'm not saying the engine has been knocking its entire life probably more than likely just recently.

It could well be an oil problem be it the oil or the pump which is the issue.

It'd certainly something to check.