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

[bourne2bongo]

Hello Everyone - we bought our lovely V6 a couple of weeks ago and have already been through a few tanks of petrol cruising and camping across the south of England. It's been awesome!

At the beginning of yesterday's road trip from Bournemouth to Gatwick (with 8 seats filled - seems I've become a taxi driver for nearest and dearest), a horrible knocking started while still driving in town. I stopped the engine, checked water expansion tank, oil (again - new van so checking every trip), and decided to take it steady but it would be okay.

The noise went away along the motorway - no loss of power in the engine - doing a steady 60mph, until I pulled up at passenger drop off, when the knocking started again. Pulled over, flipped the front seats, checked pipes heating/vacuum pipes, oils, expansion tank - again. Seemed intermittent, so did the return journey. Again - no noise along the motor way, van ran sweet, until coming to the slower roads by the sea.

On starting up today, no knocking for first couple of minutes (phew), then it started up again . I spent a few hours reading the forum but couldn't see an exact match for the problem.

https://youtu.be/TWwXf-VhCeM

This video shows the noise at tick over, and it stopping after 2000 rpm. Also noticed that when accelerating firmly, or going over 50mph, there is no noise. The noise was more pronounced when decelerating or in neutral at slower speeds. Hard to miss it. It sounds like a Massey Ferguson!

I went over engine / exhaust manifold, etc with stethoscope (based on advice in the forum). Although I could hear a distinct, sharp knock I couldn't isolate its source; not even sure if it top or bottom of engine ... sounded a lot fainter in the gearbox but still audible there.

There is oil in one of the spark plug recesses - furthest left in video - but I'm not sure if this matters. I cleaned the oily recess with rag, then tried removing spark plug leads one at a time with engine running but didn't affect the knocking ... just made the engine slightly lumpy as it went from 6 to 5 ... seemed to be consistent drop off for each plug.

Would appreciate any or ideas of what to try next to diagnose.

[Bongolia]

Judging by the speed of the knock I would think its camshaft related, the fact that it tends to die away when revved may indicate low oil pressure/ lash adjusters emptying?
I think it might be best to get oil pressure checked and the rocker box off to see whats going on.
Dont think it would be advisable to drive it much until you can pin point what it is exactly.
Oil level good?

Edit.
Just listened again on the tv and I think you have the knock there at higher RPM too.
Check aux belts pensioner for flapping about but I would get that to some one to take a good look.

[mikeonb4c]

There is oil in one of the spark plug recesses

This rings a vague alarm bell in relation to leaky camshaft oil seals, a known v6 issue. Maybe v6 experts can comment on this and possible ramifications.

[bourne2bongo]

Thanks for the quick responses bongolia and mikeonb4c.

Oil level is good according to the dipstick. Looking at the service history, last engine oil change was recent (Feb '17). Not sure if the right oil was used though. As knocking starts once warmed up, maybe oil used was wrong. Do you think it's worth changing?

Oil pressure light goes off after turning over and running- so hopefully pressure is not too bad...

Seems the Bongo uses a custom thread for the oil pressure sender switch, so any recommendations on where to pick up an oil pressure gauge that fits would be appreciated. Or failing that a Bongo-friendly mechanic near Poole / Bournemouth with the kit?

All drive belts seem to have tension. Aircon drives well when switched on.

More service history - looks like cam and crank seals were replaced back in 2013 by Janner Pit Stop garage, Cornwall.

Will take the rocker cover off next and see what's underneath. Any suggestions which cover to take off first e.g. driver or passenger ?

[Northern Bongolow]

as said above check the belts and pulleys are ok, check the crank pulley is attached ok too, could be the crank pulley bolt loose and tapping on the front of the engine, look for swarf in the area and see if it will turn independent of the crank.

http://lushprojects.com/bongopartsmk2/c ... no=.html#4

[bourne2bongo]

Cheers for the suggestions Northern Bongalow.

Is it best to check belts like this from underneath (removing padded floor pan thingy first)?

[rita]

Personally I would check the oil pressure, particularly when warm, even when your engine is cold there seems to be a rumble .

Good Luck.

[bourne2bongo]

I'd like to check the oil pressure too, Rita.

Any recommendations of where to get an oil pressure gauge kit that fits the Bongo?

[rita]

You should be able to purchase universal kits from your local motor factor/accessories shop or the old favourites Amazon or Ebay.


Good Luck.

[Bongolia]

I'd like to check the oil pressure too, Rita.

Any recommendations of where to get an oil pressure gauge kit that fits the Bongo?

Have you a garage near you that could look the van over and carry out the oil pressure check at the same time.

[bourne2bongo]

Thanks Rita. Thought I'd read on here that the thread on the oil pressure sender switch is an odd one? I guess 'Universal' should fit anything - I'll pick up a kit today

I had booked in the Bongo for the once over with Vaughan at AVA but as it's a 100 miles trip each way, I'm thinking that's not too smart now.

I see South West: RD Motors (Poole) advertise on here and seem to have a history with Bongos, and they're just up the road. Not seen them mentioned in the Members Area or forum (good/bad thing?) but may give them a try once I've had a look over the belts.

Thanks again for suggestions and ideas. I've been reading this forum for hours and hours over the past few months - the community here is awesome!

[rita]

If you are looking for the correct thread size/pitch ,the PN for the switch is JE4818501A ,your local shop should be able to match this to a suitable kit adapter.


Good Luck.

[bourne2bongo]

Cheers Rita. I'll let you know how it goes.

Like I said, the knocking seems to be an intermittent condition. This video was shot right after the previous one, and it sounds different.

https://youtu.be/kSgGns-sKSI

Also in this video, I found out what one of the magic switches does. The low-beam headlights switch off (dim) when the comes to a stop, like at a junction. It's disconcerting if you're not expecting it. This switch disables that 'feature'

[Bongolia]

You mentioned you had a stethoscope, if you put this on the stationary centre bolt of the aux belt spring tensioner do you hear the noise?
If auxiliary belts and tensioner are ok then you need to look at the timing belt tensioner and belt next before removing rocker cover. Not sure if this doable through an inspection hole or not or if the top cover can be remove to facilitate this. Someone on here will have the answer to that.
It should have very little play, then with the engine running check there is no flapping of the belt when revved.
Is there any record of the cam belt being changed?
Looking at RD`s website they do claim to have knowledge of Bongos if they are that local then maybe drop in and ask them to put an ear on it, may save you a lot of grief in the long run.

[bourne2bongo]

Thanks for the step by step, Bongolia.

I've got a few days off (was planning a camping trip!) so will get the van up on axle stands, remove the underside plastic engine cover and get up close to the belts with the scope.

Video to follow no doubt!