Cooling Help Please! At the end of my tether :{

[Manxda]

it would be best to pressure test the whole system before you bleed it again, it will not bleed up right if it has a leak somewhere.
get an old rad cap and cut through the bottom seal and disc so that it does not seal against the bottom seal point in the exp tank but still seals at the top seal at the neck.
attach a 2 bar pressure gauge and pipe to the expansion tank over flow pipe then fit an old car tyre valve into the end, this will allow you to inflate the whole system to no more than 1 bar with a bike pump, remove the pump, the valve will hold pressure and watch the gauge either hold pressure for a min or two or slowly drop pressure, if it drops you have a leak somewhere so you should see it leak with 1 bar of pressure pushing out the coolant. if no leak is found but pressure is dropping suspect a crack in the head.
to make sure its the head remove the glow plugs on cylinders 2 and 3 then get a few dry strips of paper from your paper shredder and dip them into the cylinders to see if they get wet.
shout if you need more how to make stuff info.

Thanks. Great advice, I'll give that a go.

[Manxda]

This could be cheaper than paying a garage:

http://www.ebay.co.uk/itm/like/33171824 ... 4071953993

This is a Chemical block test kit, the Sniffer test is using a Gas Analyser over the expansion/header tank to take a Sniff (sample) which will or not confirm the presence of combustion gasses in the coolant.

Good Luck

Thanks, I'm going to need it!

[Manxda]

I was at my mechanic Adrian at Japandirect in Bury a few years back. He was dealing with a Bongo that had crudded up radiators and he was replacing both main and front heater radiators. I also recall people on here doing research on the Bongo coolant system and determining that the front heater radiator was an important part of the circuit. Seems a strange idea to me but I'm sure Adrian wouldn't mind you calling him on 0161-763-3003 to ask him what he thinks. He's a Bongo expert of many years standing. Of course if channels in the engine block are crudded I'm not sure what you do. I wonder whether one bodge might be an engine block temp gauge and either link rad fans to activate from the temp gauge or else with a manual override switch. Not fixing the cause but might prevent system going critical.

Thanks, I'll give him a call.
Cheers

[Manxda]

If the coolant is being 'blown'out of the header tank it is probably because the system is being over pressurised by exhaust gasses entering the system via the cylinder head cracks.

The logic is good and would explain why it's doing this without the thermostat opening.

[Manxda]

Firstly, thanks to everyone who has offered advice - it is very much appreciated, even if some of it is not what I wanted to hear. Cheers.

So, had another go at bleeding again on Saturday, with the help of my missus this time. It took over 2 hours, but finally bubbles stopped. I'd done the 2.5k rev thing to get the thermostat open and kept on with the bleeding process for another 20 mins after the last bubble. All was looking well. Took it for a drive with mixed driving (around the village, down a fast bit, back around the village again. All good with 11 o'clock on the temp gauge.

Next morning, checked header tank and all was well. Fired up and left running for 5 mins. Still good. Went off down the road and stopped after a mile. No water coming out of overflow. Carried on and after 1/2 mile temp gauge decides it's more comfortable at 1 o'clock. "Oh dear, what a shame" I said (or words to that effect). Turned around and headed back home and the gauge goes back to 11. So, I carried on my journey for another 10 miles and headed back. No problem. Great! It was just a stray air bubble eager to join its mates, I thought.

Later that day, another trip - 5 miles out, 5 miles back. All is good until on the way back temp goes to 1 o'clock again. Took it steady to nurse it home but it was having none of it and temp gauge went for the big 'H'. Pulled over and had a look up front - water pouring out of header tank. Decided to let it cool down and then top it up, but I'm on a narrow country lane and after 3 or 4 minutes a van comes up behind me wishing to pass. I reluctantly start up to move down the lane to a passing place and notice that temp is back to normal. Crazy! Anyway, I drove home (about 4 miles) and it was okay until I was almost home and the gauge started to rise again.

If the scrap yard had been open on Sunday I would have driven straight there, although I have calmed down now and am having another go. Today I checked the bottom hose, below the stat, and could see a lot of crud around the joint. Could this cause such an issue as this? Sorry, picture wouldn't attach even though it is only 480px and 24k! I had a similar issue a couple of years ago and traced it to a tiny pin-hole in one of the small pipes coming from the head. Changed that, bled it and all has been well until now.

I'll replace the hose, do a pressure test and give the bleeding thing one more go (interpret as you wish). Still can't find a mechanic to touch it

Plodding on

[Northern Bongolow]

you really need to establish if the cooling system is air and water tight by doing a pressure test, repeated bleeding of a system with any leak may kill it off.
boiling like you describe is usually down to no flow or poor flow of coolant, this can be a physical blockage in a pipe or one of the heater matrix, or more commonly an air lock, or a drop of pressure being held inside the system. if the header tank cap is not holding the ness pressure (about 7-10 pounds) when up to normal running temps it will boil, if the coolant is not circulated it will boil, if there is a blockage it will boil.
you could remove the bleed pipe bung and fit a 2 bar pressure gauge into the end and drive it to see accurately what pressure is created in the system while driving with the passy side seat up.
temp is only measured locally, that is where the temp gauge is fitted, pressure is a measurement of the system as a whole.
it sounds like yours may be failing as it reaches the control temp, that is to say once up to running temps, but once it reaches this it is not being controlled, this could be faulty stat, sticking or late to open, fans not cutting in, fan switch in the side of the head faulty, blocked rad, or a leaking pipe somewhere that is letting out the cooling system pressure, this allows the coolant to boil at a lower temp.
one of the hardest coolant leaks to find is the water pump, have a read of this good thread it explains how to check the water pump.
http://igmaynard.co.uk/bongo/forum/view ... ak#p572266

[Bongolia]

you really need to establish if the cooling system is air and water tight by doing a pressure test, repeated bleeding of a system with any leak may kill it off.
boiling like you describe is usually down to no flow or poor flow of coolant, this can be a physical blockage in a pipe or one of the heater matrix, or more commonly an air lock, or a drop of pressure being held inside the system. if the header tank cap is not holding the ness pressure (about 7-10 pounds) when up to normal running temps it will boil, if the coolant is not circulated it will boil, if there is a blockage it will boil.
you could remove the bleed pipe bung and fit a 2 bar pressure gauge into the end and drive it to see accurately what pressure is created in the system while driving with the passy side seat up.
temp is only measured locally, that is where the temp gauge is fitted, pressure is a measurement of the system as a whole.
it sounds like yours may be failing as it reaches the control temp, that is to say once up to running temps, but once it reaches this it is not being controlled, this could be faulty stat, sticking or late to open, fans not cutting in, fan switch in the side of the head faulty, blocked rad, or a leaking pipe somewhere that is letting out the cooling system pressure, this allows the coolant to boil at a lower temp.
one of the hardest coolant leaks to find is the water pump, have a read of this good thread it explains how to check the water pump.
http://igmaynard.co.uk/bongo/forum/view ... ak#p572266

Manxda
Do the fans cut in?

[the1andonly]

Do fans cut in.
where do you measure volts when fans cut in?
1st speed
2nd speed

[scanner]

Morning All
Well, my 2.5TD has been overheating (again). Thought it had sorted itself out a few months ago after a thorough bleeding session. Apparently not. It started again, out of the blue, a couple of weeks ago. Running fine over the Mountain Road at 60-70mph but as soon as I slowed down to 30 the temp gauge exited right. Pulled over and switched off. Fans on and water initially pouring out of header tank. Anyway, managed to get home (eventually) and this is the order I did stuff to rectify the problem:
1. Topped up bled the cooling system as per proper procedure. Worked for about 5 miles with the gauge at 11 o'clock and then went ballistic. Turned on the heater - cold. Water out of header tank
2. Checked the bottom hose - cold. Replaced the thermostat with genuine Mazda part (what a ball-ache!). Top hose was looking a bit tired, so I replaced that as well, bled system. Bottom hose got hot (thermostat open) - ran okay for a few runs, thought I'd fixed the problem then, boff! - overheated again, seemingly at random, not doing any hard work, 40mph. Water out of header tank but not empty, as usual.
3. Checked everything over again and noticed that the new radiator installed about 10,000 ago had a pressure cap rated at 0.9. Changed that for a new 1.1 and did a couple of trips to town and back (5miles each way). Wahay! seems to be working. Went out this morning and overheated again after a couple of miles. Oddly the gauge went to about 1 o'clock and stayed there.
So, what have I missed or am doing wrong. Water pump was replaced a couple of years back (8k miles). Any ideas gratefully received or the Bongo is going to have an appointment with the Wicker Man!
Cheers

That is actually one of the worse things you could have done.
Turning the engine off so that the coolant ceases to circulate will cause massive heat soak as all the heat still in the engine goes straight into the coolant in the head and block and boils it. That will often cause the explosive boiling over you saw.
Much better to leave the engine ticking over and spread the heat through all the coolant and keep that circulating through the rad.
Even better open up all the heaters on full heat and put the fans on full as well to dump as much heat through the heater circuit as possible.

[cushers]

If it was cooling ok at high speed and therefore lots of air over the rad, could it be a water pump?

[Gasy]

How dirty is the coolant after it's been in for a couple of days
Have you flushed the system through with a hose pipe to check for blockages