Knocking Noise from left side of engine... PLEASE HELP!

[Jamie25]

It seems to be one thing after another with my van at the moment!

Developed a leak from the water pump so replaced that and thougth I'd replace the expansion tank and level sensor at the same time as the tank had developed a small crack. Replaced with a GSF one and bled the system, only to find that the cap isn't sealing. I tried to tighten it further and it seemed like it went past the bottom of the thread on the tank, ie. it went loose and could be turned further before re-tightening. Also I think I overtightened the level sensor as it's leaking from there! At least the new pump seems not to leak - yet! So now I can't decide whether I should get a genuine tank from VW or a cap from GSF? I'm leaning towards VW....

And whilst I was doing this I realised that the left bank of cylinders has developed a nasty loud knocking noise. Doesn't seem to be from the head but from the 'bottom end' as it were. On having a look around I noticed a gaseous leak from the left rear exhaust manifold. Could this loss of back pressure be causing timing issues and hence the loud knocking? The other side of the engine seems to be running smoothly and I've not noted any real loss in power on a short run.

The van was running okay and is booked in with Gasure on Friday for a carb re-build and LPG tune up, but I guess there's not a lot of point in that if the engine is on its way out!

Any advice greatly appreciated...........

[Jamie25]

Should have said - it's a 1987 petrol 1900DG engine......

[Mushr00m]

Knocking noises(especially from the bottom end) are usually a good
indicator that your "Big End" bearings have gone. Sorry.

Unless the stone shield is loose, I'd seriously investigate
further ASAP.

Try draining your oil & checking for shiny flakes of babit(lead & tin)
bearing material in it.

[kevtherev]

is it a loud tack tack, tonk tonk or donk donk?

big ends clonk or dunk louder under load

I would bet my house it's a tappet, usually noisy after a lay up or short runs.
Might be good to change the oil and filter to 20w 50 mineral.. tends to quiet a noisy tappet

[boatdog]

if it was the big ends it would be from from the middle of engine not from one side or the other, id go with tappets just drained them selves

[Jamie25]

Tack or a Donk.......

I'd have to say its a tack or a tic, and definately NOT a rumble. The van has been sat up for a weekish so I'll hope it's the tappets. I guess an iol change, a new gasket on the manifold and make a decsion on the expansion tank/cap situation. Just hope I don't bugger up the manifold stud!!!

[Mushr00m]

If it sounds like a slow sewing machine, it'll be the tappets.
Just top up oil & go for a run out.

Knocking noises are usually big ends. Rumbling noises are crankshaft
main bearings.

[kevtherev]

If it sounds like a slow sewing machine, it'll be the tappets.
Just top up oil & go for a run out.

Knocking noises are usually big ends. Rumbling noises are crankshaft
main bearings.

hell it was a typo!... no need to roll the eyes man.. unless you never made an error

[Jamie25]

Thanks for the advice all.

I think I'll try an oil change, sort out the cooling system and exhaust. I guess if it's the big end or crankshaft bearings it's a full engine rebuild or engine swap. Fingers crossed for tappets - it does sound like a slow sewing machine, just a really BIG one.

Really annoyed with the GSF expansion tank. I can understand their parts not lasting as long as genuine ones but to simply not be fit for purpose it another thing entirely!

[Mushr00m]

It is your tappets. Hydraulic lifters just need re-pressurising
after it's been standing. So worry not.

The noise is rather loud & does sound really bad when you first hear
it. An oil change won't do any harm but you'll only need to top
it up & take it for a run. It should disappear within about 15mins but
may take longer.