Houston we have a problem.

[The Great Pretender]

Houston we have a problem.
I wrote that in my notebook in mid 2011 at 84400miles.
The Bongo had been loosing coolant albeit only slight for 15000 miles before that.
Well it is still running and It’s driving me mad. The amount of coolant disappearing has risen slowly but the loss doesn’t equal mileage it is more time related.
My coolant system has a float alarm in the tank, temperature gauge reading coolant exiting the head and an accurate pressure gauge.
It has been in two garages that I respect mainly to get it up in the air to inspect.
With the under tray off and paper under the Bongo in my garage there has never been any sign of a leak. I have had UV dye in the system, shows nothing.
So, where is it going? Head problem? It has now done 105000 miles, would the head have lasted 35000 miles with a problem? Also the system pressure is normal with no white smoke and only drops slowly with temperature when stationary for hours making a head problem seem remote. No loss of coolant from tank.
I like to think I can find my way around an engine but this has nearly got the better of me.
No visible leaks, no unnatural pressure rise or fall, where else to look?
Logic points me to the turbo as the culprit but the loss is not related to miles travelled, have to admit I’m baffled. Anyone got a spare turbo……………
Or advice?

[mikeonb4c]

If the loss is slight, maybe get used to topping it up (like we used to on our old cars) when alerted and just wait for it to worsen until the source becomes obvious?

[haydn callow]

Hi, you say...no loss of coolant from tank...confused !!

Could you be weeping from some HOT area and being steamed off??

I wouldn't have thought you could survive 35000 without it getting dramatically worse.

I assume yOur tank float system is defo sealed.

Have you checked underneath the tank for cracks ??

[teenmal]

Core plugs, especially at the REAR of the engine a renowned for this sort of problem/loss.

[Spencer54]

I had a Land Rover that did that for years - I read that it could be an internal crack in the block somewhere at the time and it scared me into selling it.

I spent my entire time panicking about the coolant loss.

Chap that bought it was a mech from the AA, I told him about the loss and he checked was happy that it wasn't pressurising and bought as was.

With hindsight - it probably was the core plug, but if you're getting coolant into the combustion chamber you'd see white smoke I'd have thought.

[widdowson2008]

Core plugs, especially at the REAR of the engine a renowned for this sort of problem/loss.

I had this problem (duff core plug) but wasn't aware of any coolant loss - it was just weeping and evaporated so no leak apparent. Ady spotted it. Got a new one and Ady fitted it for me.
The plug was on the drivers side toward the rear of the head. (see pic)

[weebrian]

I had a similar problem with my V6. Put up with it for nearly a year, topping up about 200ml every three weeks or so. Couldn't see where it was coming from but it turned out to be the temperature sensor leaking. New sensor, problem solved.

[Northern Bongolow]

i have a turbo if you need to do a longer term test

[The Great Pretender]

Hi, you say...no loss of coolant from tank...confused !!

Could you be weeping from some HOT area and being steamed off??

I wouldn't have thought you could survive 35000 without it getting dramatically worse.

I assume yOur tank float system is defo sealed.

Have you checked underneath the tank for cracks ??

Yes that does seem confusing re reading it. What I meant was no loss while running (pressure cap not venting). I also have the vent pipe running into a bottle.
No leaks from the tank.

I shall check the core plugs tomorrow but as I said in my original post it can take hours when switched off for the pressure to drop to zero. If there was a leak surely it would loose pressure sooner.
Thanks for the offer Ady I hope I wont need it. I have ordered more UV dye and Mike at Wheelquick has offered to go over it again

[haydn callow]

Well...maybe you do have a tiny leak via the head gasket into the combustion chambers. But I would have expected it to get worse....I'm sure with all your knowledge/experience you will have eliminated most possibilities.....annoying but perhaps you will have to live with it.

[New Forest Terrier]

I had a slight leak on mine for about six months. No sign of a leak, but a steady slow loss of coolant. It passed a hot and cold pressure test and all hoses appeared perfect. It was not until it got slightly worse and I spotted coolant on the ground behind the drivers door that it was identified as a leak from the rear heater matrix. Bypassing that cured it completely.

[Northern Bongolow]

I shall check the core plugs tomorrow but as I said in my original post it can take hours when switched off for the pressure to drop to zero. If there was a leak surely it would loose pressure sooner.

you cannot see some of the core plugs mel, and ive heard of one that blew a rear one,this was draining out of the bell housing drain with a little oil mixed so wasnt noticed easily.

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

this time of year it may take 4-5 hours to drop the pressure to zero, so that sounds about right. bit of a scratcher this eh.

[dobby]

I shall check the core plugs tomorrow but as I said in my original post it can take hours when switched off for the pressure to drop to zero. If there was a leak surely it would loose pressure sooner.

you cannot see some of the core plugs mel, and ive heard of one that blew a rear one,this was draining out of the bell housing drain with a little oil mixed so wasnt noticed easily.

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

this time of year it may take 4-5 hours to drop the pressure to zero, so that sounds about right. bit of a scratcher this eh.

Had that on mine 5 years ago, gearbox was dropped and new ore plug fitted. Coolant loss was rapid and the LCA detected the drop.

[dobby]

I shall check the core plugs tomorrow but as I said in my original post it can take hours when switched off for the pressure to drop to zero. If there was a leak surely it would loose pressure sooner.

you cannot see some of the core plugs mel, and ive heard of one that blew a rear one,this was draining out of the bell housing drain with a little oil mixed so wasnt noticed easily.

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

this time of year it may take 4-5 hours to drop the pressure to zero, so that sounds about right. bit of a scratcher this eh.

Had that on mine 5 years ago, gearbox was dropped and new core plug fitted. Coolant loss was rapid and the LCA detected the drop.

[The Great Pretender]

Ok, update, I’ve taken onboard the helpful comments, thanks guys.
As the pressure holds up for hours after stopping I assumed if there is a leak it seals when hot. So I did cold pressure test and it wouldn’t hold. As Ady says there are lots of potential leak points that are difficult to view, but can be heard so Doctor stethoscope please………… and bu99er me there was a leak on the top hose at the outlet stub. As some know my top hose is non standard and it buts up to the block anyhow a quick fix and re pressurise system to 12psi, make tea read paper and shout at the muppets at Prime Ministers questions. 2 hours latter check Bongo………still at 12psi……….
I now have a Bongo appears sound when hot and leak free when cold. It would be nice to think I have got to the bottom of the problem but it cant be that simple, next instalment will probably follow shortly.