Engine knock when cold.

[JonnyEnglish]

Hi everyone, I am new to this forum having bought a Bongo last September, it is a 1998 2.5td 4x4 Friendee, with a rear conversion.

I have a problem with it that I am hoping a member may have an answer to. When I start it up in the morning I get a knocking which seems like it is coming from one cylinder only. If I increase the revs over 1200 and above, the knock completely disappears only to return when the engine drops back to idle. After approximately one to two minutes over a period of five to ten seconds the knocking just goes away and doesnt return until the next day when the engine is stone cold. The van drives fine the engine sounds good and doesn't use oil or smoke.

This problem seems to be temperature related because on days that aren't so cold the knocking is not so loud as it is on colder days. I'm wondering whether this could be caused by a faulty injector or glowplug, I replaced the glow plugs when I bought the Bongo.

I know this seems to be an obscure problem but any help would be greatly appreciated.

[Rickster]

It sounds like it may possibly be one of the tappetts needing replacing.
A suggestion mould be to lift up the passenger seat, start the engine from cold and listen to the top of the engine carefully, if you hear a rhythmic ticking sound, the above needs replacing, all of them don't need replacement, just the one or more that's iffy.
Changing them is another issue, it's not easy, if the 2l petrol has anything to go on!

[Bob]

A big screwdriver pressed to your ear, or something like this helps...

https://www.ebay.co.uk/i/143103466257?c ... GwEALw_wcB

[JonnyEnglish]

Hi guys, thanks for responding. The noise is too heavy a knock for tappets and disappears after a short space of time, around a minute to vanish completely. I started it up today and because the ambient temperature is warmer than 3 weeks ago, it never knocked at all. I know quite a lot about cars having worked on them all my life but I can't figure this problem out. I think I might give the screwdriver a go as I'm pretty certain it's coming from one cylinder only. I think if it only occurs when the weather is cold, around zero degrees and not when the weather is warmer and the engine continues to sound OK when warm then I'll live with it and won't use it in the winter. Thank you all again for trying to help.

[JulesMartin]

I think if it's an oil circulation problem which seems to have gone with the warmer weather, I'm sorry to be a harbinger of doom but you may find the knock will come back when the van has been running for a while maybe an hour. if its a big end knock that has now gone because the metal has not contracted as much as it does when cold that tolerance will appear again when the oil gets really hot and thin. Really difficult to diagnose on diesels as they knock by nature when cold. the knock could have gone by the cold start mechanism not going into full 'cold start' or it could be due to metal components not getting as contracted as the do when cold. but at the end of the day if it's gone it's gone so "if it ain't broke don't try to fix it", enjoy the summer and see what next winter brings

[Bongolia]

OP It could be a number of things but I would agree with your first assumptions. As you have changed glowplugs I would go for those injectors. It wouldnt hurt to have them serviced in any case.