V6 - knocking in engine when not under load (video)

[bourne2bongo]

So Roy at R D Motors (lovely bloke, and seems knowledgeable about our favourite four wheels), got the Bongo up on the ramps and had a good listen earlier.

Although he's never heard that particular knocking noise before (he brought another Bongo mechanic over for a listen too, who was none the wiser) but isolated it to the area just below of the hydraulic belt tensioner. He said the engine sounds really good otherwise ...

The van is booked in to have belts and covers removed to investigate further - Roy thinks it's likely to the the tensioner itself. If the fault can be confirmed, I'll ask Roy to change the timing belt and cam/crank shaft seals, etc. Water pump was done back Feb by previous owner's garage, so shouldn't need replacing yet, I guess?

The outlook for our lovely Bongo just got a whole lot rosier ... fingers still crossed for no more major nasties.

To recap symptoms for anyone in the future:

• a loud, intermittent knocking coming from within the engine block
• typically takes a few minutes to start, whether engine is hot or cold
• different engine speeds make the knocking louder or quieter. Stopping and starting the engine - even for just a few seconds - stops the noise for anywhere from a minute or two to 10 minutes

[rita]

What was the result of the oil pressure test?.

Good Luck.

[Bongolia]

Good news it seems to be getting sorted. Did he take an oil pressure reading? Wondering if low oil pressure is preventing the tensioner pumping up?

I am thinking he is talking about the cam belt tensioner as you had checked the aux belt one.
If he is then I would not run it until he can get to it. If it loses tension and the belt jumps you could have big problems if the V6 is an interference engine. Still wouldnt run it even if it were not.

Edit Just looked on the Lush site that tensioner looks very like the old Ford DOHC ones. They wear and let by the oil so that may be what you are seeing coming out around the crank. I really wouldnt run that until its looked at.

[bourne2bongo]

Cheers again for your thoughts on this Bongolia. You're right: cam belt tensioner it is, and not driving is a VERY good idea!

I'll sit tight for a week ... goes in to the garage 8th May. Shame to miss the Bank Holiday camping trip, but with luck, we'll ride again

[rita]

Come on spill, what was the result of the oil pressure test??

Good Luck.

[bourne2bongo]

No oil pressure test yet, Rita. Roy squeezed me in on a busy Friday afternoon and seemed confident that problem was unrelated to oil pressure.

It will be the first thing done when she goes back in to the garage though.

Note to self: avoid scary engine noises near to spring Bank Holidays, and if that's not possible, then be patient!

[windywatson]

The V6 cam belt tensioner is a self contained unit. It doesn't rely on oil pressure to tension the belt. It contains a small but powerful hydraulic ram, which when purchased new is held in by a pin. Once installed the pin is pulled out releasing the plunger to actuate on the tensioner & tighten the belt. It is very much like a miniature ram like those used to pop up tailgates and the like. Which is why it is very important to have replaced whenever carrying out a cam belt change as they don't last for ever & if they leak & fail it will cost you your engine. However they are very costly at £165 + & that may deter some from replacing them.
I have 2 V6 vans & can tell you that it is a costly mistake to make not replacing them. If you are carrying out a belt change you need to do the lot whilst the covers are all off, Water Pump, cam shaft & crank pulley oil seals, hydraulic tensioner & all associated cam belt pulleys. Its a costly job when you chuck in a days labour, but not as costly as a new engine. It is also worth getting the auxiliary belt tensioner bearings done to as from experience they get quite noisy when warn.
This particular problem on this thread sounds like the cam belt flapping & catching the case somewhere. So guess that there’s been an oversight on the replacement of parts on a previous belt change.
Best of luck with the fix & keep us posted.


Cheers

[Bongolia]

The V6 cam belt tensioner is a self contained unit. It doesn't rely on oil pressure to tension the belt. It contains a small but powerful hydraulic ram, which when purchased new is held in by a pin. Once installed the pin is pulled out releasing the plunger to actuate on the tensioner & tighten the belt. It is very much like a miniature ram like those used to pop up tailgates and the like. Which is why it is very important to have replaced whenever carrying out a cam belt change as they don't last for ever & if they leak & fail it will cost you your engine. However they are very costly at £165 + & that may deter some from replacing them.
I have 2 V6 vans & can tell you that it is a costly mistake to make not replacing them. If you are carrying out a belt change you need to do the lot whilst the covers are all off, Water Pump, cam shaft & crank pulley oil seals, hydraulic tensioner & all associated cam belt pulleys. Its a costly job when you chuck in a days labour, but not as costly as a new engine. It is also worth getting the auxiliary belt tensioner bearings done to as from experience they get quite noisy when warn.
This particular problem on this thread sounds like the cam belt flapping & catching the case somewhere. So guess that there’s been an oversight on the replacement of parts on a previous belt change.
Best of luck with the fix & keep us posted.


Cheers

Surprised it doesn't come as part of the kit but it dont! Blueprint do an aftermarket one at 98.00+the dreaded VAT.
Checked the Ford one and I incorrectly said it was oil pressure reliant it aint it is the same ratchet out type as Windy states but is used on their chain driven DOHC engine old Scorpio shape with the droopy eyes. Has anyone got an image of the V6 one as it may well cross over and they are likely to be far cheaper (30.00 quidish IIRC) if still in manufacture. I could then get one sent down for a Ford and check it out.
Could be a good saving for future V6 Bongo owners.

[bourne2bongo]

The Bongo's finally been up on the ramps, timing belt covers removed, and the noise tracked down to the tensioner pulley. Should be fixed with a replacement (or maybe only new bearings). This clears up the mystery of the where the knocking was coming from, and no harm done

5 new seals on order, along with new timing belt, cam belt pulleys and hydraulic belt tensioner. Phew

Big thanks to all who have offered advice and guidance on here. You're a real bunch of gooduns!


The sting in the tail:

The oil leak was also tracked down to the crank shaft seal. This should be fixed as seals will be replaced, except Graham at RD Motors found some silicon behind the existing seal ... but that's another story that appears to involve a bodge job with a screw driver and some soft aluminium casing. I'll start a new thread for that one ... I might need a bit more advice from you kind folks!

[mikeonb4c]

V pleased to hear it's getting sorted and thanks for the update, which should help others

[Bongolia]

The Bongo's finally been up on the ramps, timing belt covers removed, and the noise tracked down to the tensioner pulley. Should be fixed with a replacement (or maybe only new bearings). This clears up the mystery of the where the knocking was coming from, and no harm done

5 new seals on order, along with new timing belt, cam belt pulleys and hydraulic belt tensioner. Phew

Big thanks to all who have offered advice and guidance on here. You're a real bunch of gooduns!


The sting in the tail:

The oil leak was also tracked down to the crank shaft seal. This should be fixed as seals will be replaced, except Graham at RD Motors found some silicon behind the existing seal ... but that's another story that appears to involve a bodge job with a screw driver and some soft aluminium casing. I'll start a new thread for that one ... I might need a bit more advice from you kind folks!

Naughty, naughty, very very naughty.

[bourne2bongo]

mikeonb4c - Very happy to share. I've learnt a lot from other's sharing here ... warts and all.

Bongolia - You're a firestarter, twisted firestarter ... and I'm furious! Details and a pic of the damage here ... http://igmaynard.co.uk/bongo/forum/view ... =3&t=73623

[windywatson]

Lessons to be learnt by those who will just change the belt & not all of the ancillary items that get just as much wear as the belt.

[bourne2bongo]

It's taken quite a while but I'm over the moon to confirm she's back on the road! HOORAY!!

The main delay was replacing the oil pump, which had to come from Japan - they don't seem to be a common fault on our wagons so no-one holds new stock. When it arrived a couple of weeks later it didn't include the gasket. So another two week round trip was delayed things!

All sorted a couple of weeks back - a huge thanks to Roy and Graham at RD Motors for all their patience and skill - and I'm very happy to confirm not a single drop of oil has leaked after a couple of hundred miles of testing!

Going back to the original knocking (in this thread title), this has now gone, and was definitely caused by the hydraulic timing belt tensioner beginning to fail. So along with new timing belt, and the hydraulic tensioner, all pulleys have been replaced, and of course the crank and cam shaft seals.

A few other bits also got tidied up, including a few of the heating pipes, and some welding on the front cross-member and one sill (plus a couple of new bulbs), and she's now MOT'd for a year and purring like the V6's kittens do (such a lovely engine!).

So after some heart-racing moments, and lots of support and guidance from this awesome Bongo Fury, we're good to go again. Next week we're of to S. Wales for a week, and a few weeks later down to Devon and Cornwall. If that goes well, a 6 week trip to Spain and Portugal is planned from early September. And THIS is why all the money and heartache is worth it: to get BONGOing on the open road!

[mikeonb4c]

Great news - enjoy