What's a logical sequence of investigations for coolant loss

[jimmo62]

After a long run a month ago I had the coolant escape through the pressure cap of the expansion bottle. The coolant alarm let me know and after refilling it seemed OK and a pressure test suggested no major leaks. However I took it to a Bongo expert who could not find any leaks and we decided the best bet was to replace the radiator, water pump (which looked a bit suspect) and thermostat. The guy is an expert so knows how to bleed etc. so I was happy that it came back properly bled.

After this work the system keeps pressure for much longer than before (e.g. for a few hours rather than a few minutes) so pretty sure something was fixed! However it seems that randomly it now loses water on long runs - sometimes it's fine and other times after cooling down it may lose up to a litre on a couple of hour run. I reckon that if the head gasket had gone it would always lose water - or does it depend on some other factors?

So I'm trying to work out sensible next steps. No visible leaks. I'm thinking of getting a test kit which detects exhaust gas in the coolant in case there is a head gasket problem, and also a fluorescent test kit to see if I can detect any leaks. Any other good ideas?

Finally I have a side conversion and don't need the heater for the rear, so can I bypass it in case the leak is from in there? If so which pipes would I bypass/link together?

[Steptoe]

I was also seeing coolant loss, but pressure tests were fine apparently. I have, however, noticed damp patches under the car when cold. I was suspecting the water pump as there was a rattle when starting from cold. I now suspect the pump is leaking when cold, but seals OK when the engine is warmer, so am about to change the pump. It is not necessarily the loss of coolant, but the potential intake of air that concerns me. I had to bleed the system before driving home a couple of days ago. When preparing for that, I noticed that the crank pulley was wet and stained rust-coloured suggesting that coolant is indeed leaking down onto it. Whilst bleeding it, I noticed that the crank pulley dried out. Either through the engine heat, or a seal doing its job.

I have it booked in next week for a new water pump plus a number of other jobs at the same time. I am hoping this will sort it!

[Northern Bongolow]

After a long run a month ago I had the coolant escape through the pressure cap of the expansion bottle. The coolant alarm let me know and after refilling it seemed OK and a pressure test suggested no major leaks. However I took it to a Bongo expert who could not find any leaks and we decided the best bet was to replace the radiator, water pump (which looked a bit suspect) and thermostat. The guy is an expert so knows how to bleed etc. so I was happy that it came back properly bled.

After this work the system keeps pressure for much longer than before (e.g. for a few hours rather than a few minutes) so pretty sure something was fixed! However it seems that randomly it now loses water on long runs - sometimes it's fine and other times after cooling down it may lose up to a litre on a couple of hour run. I reckon that if the head gasket had gone it would always lose water - or does it depend on some other factors?

So I'm trying to work out sensible next steps. No visible leaks. I'm thinking of getting a test kit which detects exhaust gas in the coolant in case there is a head gasket problem, and also a fluorescent test kit to see if I can detect any leaks. Any other good ideas?

Finally I have a side conversion and don't need the heater for the rear, so can I bypass it in case the leak is from in there? If so which pipes would I bypass/link together?

my first thought would be fit a brand new expansion tank cap.
i made a test rig that i take to meets etc, when i test peeps caps over half seem to blow off early, the poss 1,1 bar pressure inside the system when hot is crucial, without the pressure the coolant boils at a lower temp.
if your going to the bash i will test it for you.

second thing to check is have you got jubilee clips fitted to hoses, these are not the best thing to use on a bongo, they get hot then stretch, then leak when cooling, tighten them up, they stretch again or crush the rubber pipe--repeat, repeat.
fit only constant pressure/tension clips.
http://www.google.co.uk/imgres?imgurl=h ... =0&ndsp=26

[Northern Bongolow]

I was also seeing coolant loss, but pressure tests were fine apparently. I have, however, noticed damp patches under the car when cold. I was suspecting the water pump as there was a rattle when starting from cold. I now suspect the pump is leaking when cold, but seals OK when the engine is warmer, so am about to change the pump. It is not necessarily the loss of coolant, but the potential intake of air that concerns me. I had to bleed the system before driving home a couple of days ago. When preparing for that, I noticed that the crank pulley was wet and stained rust-coloured suggesting that coolant is indeed leaking down onto it. Whilst bleeding it, I noticed that the crank pulley dried out. Either through the engine heat, or a seal doing its job.

I have it booked in next week for a new water pump plus a number of other jobs at the same time. I am hoping this will sort it!

the pump usually leaks when cold, then seals as you say when it get hotter, this is helped by the pressure inside the cooling system.
get a dentist type mirror then look at the 6 oclock position on the pump casting behind the pulley, you may see a clean coolant trail down the casting. shine a torch at the mirror to help see it.