knocking noise on startup

[joneseymagic]

Can anyone tell me what this could be.

I have a 1981 t25. It was parked on a slight uphill, and when I fired the engine there was a loud "dat dat dat dat" metallic noise from the engine. I checked the oil level which was between min & max, and then put in an extra litre of oil, and it still persisted. I took a risk and drove it around the block, and the noise stopped.

This happened about 9 months ago, when the oil was low, and stopped when I put a couple of litres of oil in. I've never heard it again until today. I wonder if the oil was low but appeared higher because the van was at an angle? If this was the case, what caused the noise?

Any suggestions gratefully received!

Dave

[T3teedub]

Most likely hydraulic tappet has drained it's oil.
An oil change may be due and use a heavier oil, 15/40 or 20/50 if it's a high mileage engine.

[joneseymagic]

Thanks for the advice - I'll start with an oil change!

Best

Dave

[clartsonly]

the tapping will stop after about 20 miles drive, mine comes on occasionally depending how long it has been standing. it is a common issue with T25's..

[T3teedub]

Basically, it's a design fault. Hydraulic tappets should be vertical to retain the oil in them. These engines lay horizontal so the oil is able to seep out.
Having said that, certain other VW engine types, such as Golfs, have similar issues.
As clartsonly says, the oil is usually forced back in after a while and the knocking stops. Fresh oil helps though.

[ermie571]

What do you do when its been stood for months....and running it and fresh oil hasn't done the trick???

Emma

[T3teedub]

It would be best to start it occasionally and run it for twenty minutes or so. Run it for only a few minutes can cause other issues.
Give it a good half hour run at some decent revs and it should settle ok.
If it doesn't then you may need some mechanical help.