Worrying knocks

[51ab]

Hi All

Just travelling along about 50 mph in top ( Auto BW65 box). Engine has been spot on. No overheating etc and sounding great. Suddenly, it felt as if I had run over a piece of wood and it had hit the gearbox/engine ( loud bang). Looked back but nothing so stopped a little way down the road. Everything seemed OK so went to drive off. After about 2 seconds a loud knocking noise came from the engine, so I shut off, the noise went off on tickover. As soon as I revved the motor it had a loud knock but not all the time, not even at certain revs.
It will start fine but I just called the breakdown guy and he transported me home. I do not really want to start the motor in case of further serious damage (even more than it is). It is certainly strange. The noise comes intermittently but very loud almost clanking then suddenly disappears. The motor seems to be running OK but clearly there is a serious problem. The transmission is not engaged when the noise happens so I guess it is engine related. It almost feels as if some component has come loose or broken?

Any help from you guys would be greatly appreciated. Sorry it is such a long tale but that is as it happened


Cheers guys.

[jleyton]

I rather doubt yours will be as simple as this but my viscous coupling made one hell of a noise - clanking and banging - when the bearing failed. Worth a look - I hope it's this for your sake but not too sure I'm afraid.

Cheers

Julian

[51ab]

Hi Julian

Thank you for replying.

Would you know if the viscous coupling could make that sort of noise with the car static, out of gear with just the engine revving?

Thanks

Austin

[jleyton]

Oh yes, it definitely could.

To check if it's this, you've just got to grasp one of the blades (with the engine off ) and try to rock the unit. There shouldn't be any noticeable play. Unfortunately, bearing failureis likely to be progressive rather than the sudden failure you described.

Good luck.

Cheers

Julian

[RogerP]

I agree with Julian, sounds like viscous coupling.
Roger

[51ab]

Hi Roger

Being a sad g** I have just gone into the garage to check the V.C It seems OK a little play but not bad.

So, I bit the bullet and started her up. It started fine I revved up slowly and there it was, a knocking/grinding noise ,but only after five or six seconds and it disappeared then came back again. Then it happened. I felt water on my bare feet. I looked underneath and water was pouring out of an area just around the oil filter on the left hand bank(viewed from front), but I have no ramps, so could not see exactly where it was coming from.

After stopping originally and shutting off, before the car was transported back on the breakdown vehicle, I looked to see if there was any oil/water on the floor and there was none. So, it has only just started pouring water out. I guess I now need to get it on the ramp and find out the problem. Any ideas?

Thanks

Austin

[RogerP]

Hmmmm sorry but that doesn't sound good, could be water pump failure, is there water in the V?
Roger

[stag-phil]

Hi Austin

Fingers crossed that it’s nothing serious. I initially wondered if the starter motor had failed and under certain conditions it was engaging/knocking the flywheel as that may explain the noise. But the presence of water would suggest a problem with the water pump although I would have thought that would have failed completely.

Trying to be positive, maybe an engine mounting has broken and the excessive movement is causing the irregular noise and has caused one of the water hoses to fail.

Best of luck.

Phil

[Westfaling]

Austin
Have you changed or worked on anything recently on the car? Always a good starting point. The water leak sounds odd I wouldn't expect water pump failure to cause much knocking.
I'm with the other guys check the hoses and engine mounts. Then maybe remove the viscous coupling to see if it shuts up. Any sign of fan contact with radiator/shroud??
Nick

[51ab]

Hi Nick

I have checked the Vee, no water and the pump area is very dry. The engine mount idea fracturing a hose/pipe seems a great starting point as the water is definitely coming from behind the oil filter and I think it is from a metal pipe. Would a fractured engine mount cause a knocking noise at times as the engine revs? Thinking back to the original loud knock as I was driving, it could possibly have been an engine mount breaking and it could then be knocking as I rev the engine? Certainly a bit strange to get a knocking noise from a fractured engine mount but then it is a 70's British car!

No Nick, no sign of fan touching rad shroud. Not changed anything recently.

Thank you Phil for your comments too.

The saga continues.............. Thanks guys for all your suggestions.

[RogerP]

Ah just had a thought, check the bottom hose the alternator pulley runs very close to the hose, and I have had a similar noise years ago but only under certain conditions, its possible that the fan and pulley have cut/moved the hose.
Keep my fingers crossed for you.
Roger

[Seaking]

Try Checking the heater pipes that go through the bulk head for your water leak also gearbox mounts and prop shaft broken uj could cause knocking

Cheers Glenn

[new to this]

could it be a valve guide or cam bucket broke or come loose

is the knocking noise sound, coming form the top of the engine

dave

[Firept]

Have you checked the alternator mounting brackets as this can cause some strange noises when they fracture, also the metal hose from the bottom of the rad up past the alternator.
Paul.

[51ab]

Hi everybody

Further investigation on problem.

Took a good friend down with me to investigate the problem ( 40 years experience of BL mechanics), The spurious water leak, after further investigation, was a red herring. The washer bottle feed pipe had rubbed against the exhaust leaking out all its contents just as I was investigating the noise fault. After starting up again and checking the oil pressure which was fine the loud knocking noise appeared again about 1500-1800 revs. After much deliberation, it appears to be a fault with the flywheel possibly becoming loose coupled with a potential problem linked to the gearbox. The original loud noise when travelling was probably something connected with the flywheel/box becoming loose. Gearbox out in the next few days to investigate. Will update with the results.