Mechanics have run out of ideas on how to fix cooling system

[alvino]

We have a 95 Diesel Friendee that has had some recent cooling system issues.

First symptom was overheating at the top of very high hills. The garage installed a new radiator.

We drove it away and noticed that the car was running very cold as indicated by the dashboard temp gauge staying near min.
Took car back to garage where they found it did not have a thermostat. They then proceeded to install a thermostat.

Drove van away and noticed that temp was going up and down on the guage (11 o clock to 1 o clock repeatedly) and then eventually overheated with a boil.
Took it back to garage where they double checked that they had installed correct thermostat (i.e. they said it needed to be feathered). Apparently correct thermostat installed. This time they used a special bleeding machine to ensure no air in system.

We tried it again. Same problem.

Garage #1 ran out of ideas so we went to a specialist diesel mechanic who determined that there must be something wrong with the water pump. After inspecting the water pump they determined it was ok - albeit there seemed to be a little too much space between the impellers and the housing so they made some modification and bled the system and sent us away.

10ks later - another boil up. Something not right as bottom hose (from rad) stays cold. Took it back to them and they said that there could be an issue with the head gasket but they could not be confident of this as the system was holding pressure under tests and the oil looked clear of contamination. they ran out of ideas and said that a hole drilled in the new thermostat should solve the issue.

Modified thermostat does make the van drivable again. The van now runs without overheating but I am still not happy with the final solution as it seems like a bodge to me. The van now takes longer to get to temp.

What I would like to be able to do is put an unmodified thermostat back in and have the van work as it should (without a boil up).

Does anyone have any more ideas? I did notice that the new radiator has a 0.9 rad cap. Is this not high enough pressure for the bongo system? I see replacement rad caps for bongos seem to be 1.1. I did point this out to the mechanics but they assured me it was the correct cap.

Another thought I had was that maybe the fans are not coming on regularly enough. when should they come on? How do I test?

We love the van. Its pretty rare here in Christchurch, New Zealand. Any advice is appreciated.

[mikeonb4c]

We have a 95 Diesel Friendee that has had some recent cooling system issues.

First symptom was overheating at the top of very high hills. The garage installed a new radiator.

We drove it away and noticed that the car was running very cold as indicated by the dashboard temp gauge staying near min.
Took car back to garage where they found it did not have a thermostat. They then proceeded to install a thermostat.

Drove van away and noticed that temp was going up and down on the guage (11 o clock to 1 o clock repeatedly) and then eventually overheated with a boil.
Took it back to garage where they double checked that they had installed correct thermostat (i.e. they said it needed to be feathered). Apparently correct thermostat installed. This time they used a special bleeding machine to ensure no air in system.

We tried it again. Same problem.

Garage #1 ran out of ideas so we went to a specialist diesel mechanic who determined that there must be something wrong with the water pump. After inspecting the water pump they determined it was ok - albeit there seemed to be a little too much space between the impellers and the housing so they made some modification and bled the system and sent us away.

10ks later - another boil up. Something not right as bottom hose (from rad) stays cold. Took it back to them and they said that there could be an issue with the head gasket but they could not be confident of this as the system was holding pressure under tests and the oil looked clear of contamination. they ran out of ideas and said that a hole drilled in the new thermostat should solve the issue.

Modified thermostat does make the van drivable again. The van now runs without overheating but I am still not happy with the final solution as it seems like a bodge to me. The van now takes longer to get to temp.

What I would like to be able to do is put an unmodified thermostat back in and have the van work as it should (without a boil up).

Does anyone have any more ideas? I did notice that the new radiator has a 0.9 rad cap. Is this not high enough pressure for the bongo system? I see replacement rad caps for bongos seem to be 1.1. I did point this out to the mechanics but they assured me it was the correct cap.

Another thought I had was that maybe the fans are not coming on regularly enough. when should they come on? How do I test?

We love the van. Its pretty rare here in Christchurch, New Zealand. Any advice is appreciated.

Does the front heater heat up properly? Do any of the old hoses feel crunchy? And maybe you should get pressure tests done. Keep us posted and we'll try to help.

[jimmo62]

I would try the 1.1 cap as a cheap quick test

[scanner]

That does not sound like a garage (or specialist diesel mechanic) who knows much about Bongos.

Do either of them know how to bleed a Bongo cooling systems?

Did either of them ensure it was properly bled?

If not you could just have paid them to cause you a lot of expensive problems.

PS Just noticed you're in NZ that probably limits your options but watch the Youtube video on how to bleed the cooling system and get someone to follow that process exactly and I mean EXACTLY.

http://www.youtube.com/watch?v=jRAKOSxgbKo

[winchman]

Post your location as one of us will know some one near you who can help

[scanner]

Post your location as one of us will know some one near you who can help

I missed this first time....

Its pretty rare here in Christchurch, New Zealand.

Who do you know near Christchurch?

[Bob]

Post your location as one of us will know some one near you who can help

I missed this first time....

Its pretty rare here in Christchurch, New Zealand.

Who do you know near Christchurch?

Alvino.

[hijimhere]

Had the swinging gauge - which led me to replace the radiator - bleeding the system became a priority, I had pulled off the bottom hose and used a bucket to catch most of the coolant. Things began to get a bit iffy, I read that the cooling system takes 13 ltrs of 50% coolant. I used a high grade coolant and distilled water.

I bled and re-bled the system eventually I had a few tiny bubbles coming up into the bleed funnel attached to the engine bleed hose.
I made sure that front & back heaters were working and that the bottom hose was very hot.

The situation was that could only get 9 ltrs back into the system - I worked on the basis of all the advice in regard to air locks.
I had bled the system for the 5th time but could not add to the 9 ltrs already put in.

I then had a flash of inspiration - how much had actually come out of the system. I had a spare 5 ltr container which i filled with the waste antifreeze - with what was left and a bit of spillage I allowed 6 ltrs max. So it appears that the swinging temp gauge was in fact caused by lack of antifreeze, about 3 ltrs short.

Thinking back to when I collect the van - I had done a level check before getting on the motorway for the 157 mile drive home but it looks like the engine badly needed bleeding. I feel very fortunate that I didn't get an overheat and probably ruin the head/head gasket. My outlay for the radiator was not a bad idea as I got a fairly newish rad, result.

The result is good. So if you don't know the history when draining make a point of measuring what comes out. You may only get the same amount back in or like mine it may highlight a problem that was.

[PisceanJoy]

I had major problems with my cooing system a few years ago
New rad , new thermostat didnt cure it
It turned out to be some switches
Possibly a bottom of radiator I think
maybe someone more techie can comment

[alvino]

both mechanics have used various methods to bleed the bongo but I am pretty sure that they have not used the see saw method as shown on you tube. One mechanic had what he called a back bleeding machine. The other used pressure connected to the header tank to force air out of the system. Before drilling a hole in the thermostat there was definitely air in the system and the bottom hose stayed cold. Now it runs fine, albeit that it takes longer to get to temp. Can anyone explain this phenomenon?

I have new rad, various new hoses, new and modified thermostat, newish water pump that was inspected verified as working, 0.9 radiator cap

How do I rule out issues with the fans not coming on at the right time? when are they supposed to come on?

I guess I could also drain the system to see if 13 litres comes out to see if there is still air in the system, but it is somehow working just because of the modified thermostat. Does anyone know what temp the thermostat should open? Prior to drilling a hole in mine, the mechanic wanted to find one that opened earlier but couldn't

Cheers
Alvin

[wonkanoby]

you would never get all 13 litres out

[Northern Bongolow]

the stat opens at 83 dec.
http://www.mazdabongo.com/catalog/cooli ... ls-genuine.
the cap on the rad does not mater if its a 0.9 or a 1.1.------as no venting is done at the rad top, IT IS ONLY A BUNG FOR THE RAD. it is done at the expansion tank cap. THIS MUST BE 1.1 BAR.

you must make sure there is no 10mm vent pipe at the top of the rad next to the rad cap, if there is you must blank it off. there sometimes is on replacement rads. no venting must take place from the rad.

drilling the stat allows a small bypass. the bongo, and most cars work on a 2 loop system, the first loop allows the engine/heaters to get up to the optimum working temp first, then as temps continue to rise the forward movement of the bongo cools it via the rad, then when in traffic the temps rise further (no airflow through rad) the stat starts to open to blend in the second loop of cooler water into the system to cool the engine, then the stat opens fully to cool, then the first stage fans come on, if temps continue to rise the fans come on the second stage, after that it may vent at the expansion tank-------then its dead. overheat.

get a good garage to inflate the cooling system to 1.0 bar (just under the expansion cap blow off point of 1.1) and see if it holds pressure for a while. i do this via the little pipe next to the expansion cap and a cycle foot pump. the system must hold pressure or it may boil at a lower temp.

it sounds to me like it may have a little pipe next to the RAD cap. blank it off if it has.

[alvino]

I have 0.9 on radiator and 1.1 on header tank so thats probably ok. Can't see any vent pipe at top of rad next to cap. See picture linked below.

https://docs.google.com/file/d/0B8BymkM ... =drive_web

I have spoken with the garage again this morning and they have noticed that the fan is not coming on as it should. They have suggested a new thermister. Sounds plausible. They recon that the overheating previously encountered was due to this and that this in turn was causing the subsequent air bubbles after coolant was lost during boil. Does this sound reasonable to you guys. I am about to send her in for thermister replacement.

Cheers
Alvin

[scanner]

I have 0.9 on radiator and 1.1 on header tank so thats probably ok. Can't see any vent pipe at top of rad next to cap. See picture linked below.

https://docs.google.com/file/d/0B8BymkM ... =drive_web

I thought I'd read it should be the other way round so that the (higher and visible) header tank cap would blow before the (lower and hidden) radiator cap.

This would also mean that the header tank cap blowing would only vent steam - if the rad cap vents first that will vent neat, liquid coolant.

[Northern Bongolow]

i cannot see your picture mate sorry.

this is the fan switch.
http://www.igmaynard.co.uk/bongo/mercha ... tm#Coolant.
they tend to fracture where the plastic meets the metal, this gives false readings, or non at all.
make sure they fit a gen mazda one as the cheaper ones may not be as reliable, and this is an important bit of kit, it controls the warm up, the glow plugs, the auto gearbox lock up temp, the egr valve.