Overheating mystery -2.5 diesel

[Craig G]

Hi

Just looking for some pointers really about an issue with our Bongo which has previously been fine.

It wasnt getting used much during the cold spell we had during Feb / March / beginning of April but on easter sunday we decided to go out for the day. Got approx. 1 mile from home and noticed the temp gauge moving northwards. Stopped immediately and hopped out and noticed coolant pouring out the front nearside wheel area. I rolled home, literally, and rang my mechanic to tell him I had a split hose. He popped round with his pressure tester which confirmed NO leaks or split hoses, he reckons it must of come from the header tank / cap (similar area). He suggested I take it for a quick spin, got to the end of the road and temp gauge started moving again so went no further. The van had been idling for the best part of 30mins whilst pressure testing with no issues. He suggested a head test with some fluid (I'm not technically minded so not got a clue what its called and even if it'll be accurate?) but this hasnt been done yet.

Anyway, fast forward to today, he still hasn't tested it due to me being away / him really busy but he is due in the next few days. I've just been out to the van and fired it up (first time for 3 weeks) and decided to drive to the end of the road to see what would happen...well nothing happened? The gauge stayed pretty much in the same place, there was slight movement when going uphill but nothing as severe or quick as before.

Can anyone explain this? Its gone from the temp gauge moving very quickly in a short distance to not at all or slight movement when uphill or waiting for gear change.

Would the freezing weather had any effect on that easter sunday on any components, airlock created? Stat jammed?

I'm not going to jump in the van and drive everywhere without getting to the bottom of this but I'm confused.

Is there anyone local to me that fancies taking a look (I'm in De12)? Just spoken to my mechanic and he's bamboozled but then he has no real expertise on these vans.

Sorry for the long winded post!

Cheers

[ThisIsTheSea]

After having just done extensive work and problem analysis on my cooling system, I would say that you either have a blocked radiator or a faulty thermostat, or both. The cooling system needs to be well-balanced - one problem can throw it out. There needs to be a good flow through the radiator and the big bottom pipe to the thermostat. In my opinion, that's where you should start your investigations first.

[Northern Bongolow]

this sort of coolant loss may indicate a failed or failing water pump, these leak at the 6 oclock hole in the casing, this is masked by the crank pulley so is hard to spot. this lets air in, then the van is used and boils.
a leaking water pump can pass a pressure test, mine did, then failed later completely.
changing the pump is quite cheap but make sure your mechanic is familiar with how to bleed a bongo. there are 3 video's on youtube on how to bleed a mazda bongo that may help.

[jaylee]

I take it you temp gauge has been modified..? (Mason high temperature alarm/ other means.)

Second Q unrelated to the first question. Did you notice the fans cut in during the first overheating episode..?

[mikeonb4c]

After having just done extensive work and problem analysis on my cooling system, I would say that you either have a blocked radiator or a faulty thermostat, or both. The cooling system needs to be well-balanced - one problem can throw it out. There needs to be a good flow through the radiator and the big bottom pipe to the thermostat. In my opinion, that's where you should start your investigations first.

Agree wholeheartedly. That's not to rule out other possibilities, but this is such an important point and the cause, I suspect, of so many (diesel) Bongo problems.

[Craig G]

After having just done extensive work and problem analysis on my cooling system, I would say that you either have a blocked radiator or a faulty thermostat, or both. The cooling system needs to be well-balanced - one problem can throw it out. There needs to be a good flow through the radiator and the big bottom pipe to the thermostat. In my opinion, that's where you should start your investigations first.

I'll try these options, cheers

this sort of coolant loss may indicate a failed or failing water pump, these leak at the 6 oclock hole in the casing, this is masked by the crank pulley so is hard to spot. this lets air in, then the van is used and boils.
a leaking water pump can pass a pressure test, mine did, then failed later completely.
changing the pump is quite cheap but make sure your mechanic is familiar with how to bleed a bongo. there are 3 video's on youtube on how to bleed a mazda bongo that may help.

Are there any tell tale signs of the pump leaking once I have access?

I take it you temp gauge has been modified..? (Mason high temperature alarm/ other means.)

Second Q unrelated to the first question. Did you notice the fans cut in during the first overheating episode..?

Temp gauge hasn't been modified as far as I'm aware?

Can't remember if the fans kicked in, sheer panic took over!

Thanks guys, it gives me something to look for.

If it is the head would the temp gauge shoot northwards once I start driving it or is it intermittent movement. I've only had head problems once before and that was years ago on an old Rover.

[Northern Bongolow]

Are there any tell tale signs of the pump leaking once I have access?


If it is the head would the temp gauge shoot northwards once I start driving it or is it intermittent movement. I've only had head problems once before and that was years ago on an old Rover.

you can usually see with the aid of an angled head dentist type mirror a cleaned off trail that the leaking coolant has cleaned off the casting at the 6 oclock position.

if your gauge is standard then any movement above the verticle should be checked out, the gauges are really slow to respond to change,so is usually reading way below the actual engine temp.