Coolant again

[judaz]

Hi

Noticed my coolant is coming out from header tank overflow pipe.

Any ideas of how to fix it?

Thanks

[helen&tony]

Hi
Could you possibly give us a little more info.
1/. journey length
2/. gauge reading (standard or accessory gauge)
3/. has it done it once, or more times
4/. diesel / petrol and model / year
5/. any noises/ smells / other coolant episodes
6/. any puddles on the drive
plus any other info. you think might help
Cheers
Helen

[judaz]

Hi

I noticed coolant was low so topped it up about a week ago.

I drive it about 4 miles everyday and have done a few 1 hour long journeys as well this week. Its has probably been two weeks since I topped it up. I have a coolant alarm fitted very low in header tank as it naturally sits low on tank.

My bongo is a 2.5td 4wd.

I have checked pipe to radiator and is hot and temp gauge sits at 11 o clock position.

A few weeks ago I took the bongo to central france and back no problem at all.

[hijimhere]

If coolant is reaching the overflow the suggestion is that there is "pressure" in the cooling system. There might be a number of reasons for this. Starting at the easy end is there any gunge on the header tank cap or on the surface of whats on the header tank. If thats ok I would be thinking of bleeding (see video 1-2-3 on youtube) and go from there.

[judaz]

No gunk on header tank or header tank cap.

Will bleed it the weekend and see what happens!

What would put pressure in the system as I bleed the system as per videos no more than 2 months ago?

[Driver+Passengers]

No gunk on header tank or header tank cap.

Will bleed it the weekend and see what happens!

What would put pressure in the system as I bleed the system as per videos no more than 2 months ago?

Coolant, when it gets hot, expands - with the caps on tight and no leaks, that's what pressurises the system. Which is normal.

For the coolant to raise all the way up to the cap and out of the overflow, something more than the coolant itself has to be pushing it out. Air expands with heat, about 10 times more than water (I think). Water, when it boils to steam, expands rapidly (about 1000 times it's own volume). A catastrophic gurgling with coolant dripping everywhere and steam from under the bonnet is usually a sign of boiling coolant. A coolant level higher than normal, that may or may not overflow the tank gently, may be air - it may boil next time.

From what you've told us, if it was my van, I'd bleed it again before driving and then do a cold pressure test on the system to ascertain if there are any leaks.

One scenario is that either a pin hole in a hose, or a weak seal, or commonly the water pump gasket leak out coolant under pressure. When the system cools, it can draw a vacuum, which normally sucks air in a negative pressure valve in the header tank cap (at -1psi). The theory is that if a pin hole or a weak gasket/seal admits air before the tank cap does, then this can accumulate over a number of cycles, sometimes degassing through the header tank, other times settling in the head or a heater matrix. Eventually, a large enough air bubble will become an air lock, stop flow of coolant, coolant gets too hot in the head, boils, blows out more coolant, lets in more air, low coolant alarm goes off.

"Unmodified gauges" will sit at 11o'clock until it's too late. Modified gauges or aftermarket digital sensors help. Plenty on here about both.

I hope some of that helps.

[haydn callow]

Why would anyone fit the low coolant alarm sensor LOW in the tank.....it should be halfway between the low aan full lines.

[judaz]

Thanks that makes sense.

I had a cold pressure test done with a service a month or so ago and it was fine! Is there an easy way for me to cold pressure test it myself?

Thanks for all your info. I will definitely bleed it again asap.

[Driver+Passengers]

Here's how I did mine...
http://mazdabongo.wikispaces.com/Servic ... ant+System

[judaz]

Believe it or not but my coolant naturally sits very close to the low line no matter how much you top it up it goes back to that level and stays there happily. the previous owner had your coolant alarm fitted at the halfway point as you mentioned and disconnected it as the coolant would always settle below it. He as well as I have travelled thousands of miles in the Bongo with the coolant at just above the low level and it does not move, hence why I moved the alarm lower and it has come on with this new problem so it is doing the job I need it to.

Thanks for the info about cold pressure testing very helpful.

[Northern Bongolow]

good advice from mat .

a failed water pump is the hardest leak to detect, it usually only leaks when cold, and they usually pass a pressure test even when gone, the pressure seals the leak, look for a clean trail on the casting made by leaking coolant, you will need an angle head mirror like a dentist though, as the hole is behind the crank pulley.

[Simon Jones]

Never heard of a system that keeps dropping to the same point regardless of how much it gets topped up. Coolant must be coming out somewhere and if it's the expansion overflow, then there's excess pressure caused by an airlock, head gasket failure or cracked head/block.

[ffrank]

probably an air lock bleed some coolant from bleed hose under seat

[judaz]

Have bled the bongo and all is good again, no leaks and pressure test was done fine so will keep an eye on levels and see if air gets back into system.

I currently have green coolant in my bongo what make and where do people get the green coolant from?

Thanks

[judaz]

Problem has come back so air is defiantely getting back into the system. Van ha sbeen running fine since i bleed the system back in Sept.

Is the likely cause the water pump seal?

What green coolant do people use?