coolant keeps going down, low coolant alarm

[Rumple]

Hi All,

Recently my bongos coolant tank keeps emptying so the Low coolant alarm goes off. I fill it up again with ready mix OAT. IT drives fine for a couple of journeys and then empties again. Which would suggest leak, hose etc.

But I cant see anything wrong. Any ideas of what it could be?

Cheers

Duncan

[mikeonb4c]

Welcome. A slow leak of hot coolant may evaporate to leave no trace. And the leak may only get going when the system is hot and pressurised. My radiator started to leak at the seam between plastic top section and metal matrix and it was v hard to spot. So there's one prime suspect, as old Bongo radiators are very prone to failing like this. But it could be a corroded metal coolant pipe, pinprick leak in rubber hose, or water pump leak. You could try u/v dye and torch to try and trace it. Good luck and keep us posted.

[Bob]

Agree with Mike, above.

It's not unknown for a tiny hole somewhere to loose coolant slowly then allow air in as things cool down and contract.

This really must be investigated and fixed as I'm sure you are aware of the head issues if you overheat a Bongo.

[Flanners]

I have no knowledge of the Bongo HG issues, but rapidly falling coolant levels with no outward visible sign of leakage can point to HGF, usually with other symptoms rough running, mayo on dipstick/oil filler cap, excess vapour in exhaust, oily residue in coolant etc.

[Rumple]

thanks all I'll get it down to a bongo mechanic cheers

[mikeonb4c]

I have no knowledge of the Bongo HG issues, but rapidly falling coolant levels with no outward visible sign of leakage can point to HGF, usually with other symptoms rough running, mayo on dipstick/oil filler cap, excess vapour in exhaust, oily residue in coolant etc.

Yes thats another possibility. From my experience with mine when it happened, I'd expect to see very steamy exhaust, and quite possibly lumpy running on startup. Also, with Bongos, I believe mayo on dipstick is hardly ever found as (i think!) the break/crack pressurises / puts gases into the coolant (and lets coolant back into the pots on engine stop) but doesnt cause coolant to cross contaminate into oil system. Bongo experts may correct me on that though!

[john]

After buying my Bongo from someone who let a relative 'have a go' at installing a Helicoil insert to a spark plug port and bored it out to large for the size up plug I took it to be repaired and serviced by the garage I have used for years. They did the work plus renewed the coo;lant alarm which was constantly buzzing prior to the work.
Since then it has increasingly lost water and buzzed away unless the water is topped up whilst not showing any signs of a leak or rough running on startup, or excessive steam from the exhaust, or contaminated (cloudy) engine oil.

I suspect the problem is the way in which the sensor itself is fitted to the header tank. I noticed that when I tightened the sensor screw into the tank the problem ceased for a couple of start ups. Its just possible that the expansion and the following contraction of the screw allows pressure to escape from the tank.

I'm going to try adding a rubber 'O' ring to the assembly

I'll keep you posted

[Roy748]

If you opt for a UV dye, use the torch on the engine etc before adding the dye, as if the previous owner has used dye in the past the torch will see this this giving a confusing reading. As once dye has been used it's very hard to remove.

[mikeonb4c]

After buying my Bongo from someone who let a relative 'have a go' at installing a Helicoil insert to a spark plug port and bored it out to large for the size up plug I took it to be repaired and serviced by the garage I have used for years. They did the work plus renewed the coo;lant alarm which was constantly buzzing prior to the work.
Since then it has increasingly lost water and buzzed away unless the water is topped up whilst not showing any signs of a leak or rough running on startup, or excessive steam from the exhaust, or contaminated (cloudy) engine oil.

I suspect the problem is the way in which the sensor itself is fitted to the header tank. I noticed that when I tightened the sensor screw into the tank the problem ceased for a couple of start ups. Its just possible that the expansion and the following contraction of the screw allows pressure to escape from the tank.

I'm going to try adding a rubber 'O' ring to the assembly

I'll keep you posted

I've never heard of a sensor screw causing a leak before. Be careful not to overtighten and 'strip' the header tank thread. V6 are not known for blowing head gaskets compared to diesel. Are you sure its not something like a radiator leak that can be very hard to spot esp as the engine warms abd it evaporates as it exits. How quickly is it losing coolant?

[rita]

Hairline fracture on turbo could be another slim possible chance maybe?


This vehicle does not have a Turbo , unless it's an aftermarket unit.

[john]

the rubber washer fitted between the tank and electrical terminal post connector seems to have worked. it seems to be sealing the gap when hot or cold.

[mikeonb4c]

the rubber washer fitted between the tank and electrical terminal post connector seems to have worked. it seems to be sealing the gap when hot or cold.

Excellent. Still strange you had to resort to that though - never heard of it happening before.

[haydn callow]

I’ve never heard of a sensor screw not sealing. Using a rubber ‘0’ may not be a good idea. I think it will perish very quickly with the hot /cold cycles. I suggest you phone Haydn Alarms and ask Jo for a oversize sensor screw FOC. TELL HER ‘dad says’

[haydn callow]

Also check around the top of the radiator for a leak.

[john]

I’ve never heard of a sensor screw not sealing. Using a rubber ‘0’ may not be a good idea. I think it will perish very quickly with the hot /cold cycles. I suggest you phone Haydn Alarms and ask Jo for a oversize sensor screw FOC. TELL HER ‘dad says’

The sensor screw fitting doesn't form a water tight seal to the header tank, so during expansion (when the pressure is increased) and subsequent contraction the two different materials which aren't thermally coefficient can develop a gap.
I cant see a problem with using a rubber seal washer (not O ring - my mistake), after all thermostat caps use them and rubber seals are used on a lot of high temperature fittings in plumbing.
Main thing is it has worked, tested it on a 130 mile round trip last weekend, but I'll keep an eye on it.
I think a larger screw may just increase the problem, by using the rubber washer I don't need to tighten the screw so much and risk stripping the thread.