Me Again - Still overheating -what do I do now?

[Slybacon]

Refilled with coolant. Bleed using Dave's modified see-saw method. Bottom hose warm during process. Waited overnight to cool and did cool bleed - little or no bubbles. Went for a short drive 30mins (around town, up - down some steep hills). Got home and the radiator fan is running. The temp gauge was okay, at least it didn't go above 11o'clock. No strange noises. Heaters in the car hot. Should this happen (the fan running I mean)??? Is there still a problem? My hunch is yes, because I can't recall the fan running at all since I've had the van(6months). Also the original incident, before I did the bleed, was high temperature in the cab. Not so tonight, but it was persisting down - so ambient temp pretty low.

I'm really at a loss as what to do next. In the tests I have done (changing the thermostat, removing and examining the water pump) all components have been fine. The radiator seems not to be blocked (I did a test as described by Dave).

Would love to live near Allans but we're too far. Can anyone suggest a really good garage/mechanic in my area (Lanarkshire, Scotland) who has expert knowledge on Bongo problems of this nature, or suggest something else I could try?? Could it still be air in the system, for example?? I'm less interested in cost not - more interested in solving the problem.

I really need to get the van sorted asap - going to France at the end of June!!!

Any advice appreciated.

[mikeonb4c]

I'm trying to work out if anything is actually wrong. Was the heater hot simply because you had the heater set to on? Is the rad fan coming on simply because a sensor is faulty. Temp gauge is staying at 11.00 oclock - that's good except we all know it stays there until things have gone pear shaped. But still, it is where it should be. Other than having a specialist look at it I can think of only two precautions:

1) Fit an engine block temp gauge like the TM2, or the Mason alarm (although personally, and even though it is dearer, I like the idea of the engine block temp gauge - don't know I'm right in thinking that though)

2) Fit a scavenger fan over-ride switch/circuit like I've done. This isn't going to work a miracle if there really is a coolant system problem, but it should only do good and help keep the cab (and the engine block to some extent) cool by flushing heat out of the engine bay - useful in the heat of France. I've not had my mod. in action for long so can't say its tried and tested but installed properly (suitable rated wiring +ve feed direct to fan with inline protection fuse) I can't see any danger.

And keep driving it. Keep an eye on the header tank level too in case it drops for any reason (air locks coming out of the system). Also, see-saw method notwithstanding, I was happy that I followed the official Mazda workshop manual procedure, with its detailed advice on running the engine for a period at 2500rpm (or whatever it was) for several minutes, then tickover, then 2500 again etc. I reckon this is intended to ensure trapped air gets flushed out.

Hope this helps. Bongos do get hot under the bonnet - maybe the only unusual thing about yours is the rad. fan being on (did i hear it tends to come on when aircon is running - presume you've considered that one)

Keep us posted

Mike

[Slybacon]

Thanks for the ideas Mike.

I think I'll have a go at the Mazda Manual method just to see if it makes any difference. I could well still have air in the system, it is possible. The engine block temp gauge sounds like an idea too + the scavenger fan switch.

The air con definitely isn't on.

I may as well keep trying a few things myself - I might just crack it.

[maxheadroom]

The air con definitely isn't on.

My vents still allow warm air to come out when driving, unless I first turn the air con on and reduce the temp down to 18º but to stop any air coming out of the vent whilst driving I press the recycle air button (think thats what it's called), the one on the top left of the digital control unit.
Hope you get it sorted soon.

[sparkymik]

My vents still allow warm air to come out when driving, unless I first turn the air con on and reduce the temp down to 18º but to stop any air coming out of the vent whilst driving I press the recycle air button (think thats what it's called), the one on the top left of the digital control unit.

Yeah I concure with this also, BTW top tip Max on the use of the recycle function thnks for that

Sparky

[bigdaddycain]

If both front and rear heaters are blowing continuousy hot, that would suggest no air lock is present. It's encouraging to see a constant on the temp gauge too.

I'm thinking along the lines of a temperature sender switch fault.

[mikeonb4c]

Thanks for the ideas Mike.

I think I'll have a go at the Mazda Manual method just to see if it makes any difference. I could well still have air in the system, it is possible. The engine block temp gauge sounds like an idea too + the scavenger fan switch.

The air con definitely isn't on.

I may as well keep trying a few things myself - I might just crack it.

That's the spirit. And think seriously about the scavenger fan over-ride. I've a strong hunch this will result in a much cooler cab when driving in hot climates. Make sure it is fuse protected if you do try it, and of course I take no responsibility etc. as its not a type approved mod. But I'm risking it myself and am relaxed about it.

[haydn callow]

I still don't think you have a overheating problem. Perhaps a electrical/sensor fault.
Engine block/clyinder head Temp gauges TM2 Watchdog !!! Watch this space...you "may" soon be able to get them direct from me at a greatly reduced rate. This is a result of requests from forum members. You will be the first to know.

[Grahame at work]

Slybacon,

I don't think you have a problem either.

The fans can come on after a fairly short journey as it depends on the type of road / traffic conditions rather than any other factor.
The temperature of the coolant can climb rapidly when coming to a halt, as at lights roundabout etc., after a some moderate acceleration. Once switched on due to such a condition they do not switch off until the coolant has dropped in temperature sufficiently and this may not happen during 'busy' driving. So although the engine does not need the fans on as there is sufficient forward motion and engine speed the fans will be left on due to an earlier condition.

regards Grahame

[Slybacon]

Thanks guys,

Haydn - I'm really keen on the engine block temp sensor - keep me posted.

I'm (obviously) hoping that I don't have a problem but the very hot cab the other day bothers me. The handbrake was really hot and I can't remember it ever being like that before. I'm going to test the scavenger fan and sensor and see what's what.

I'll keep you all posted.

Cheers

[Aethelric]

Refilled with coolant. Bleed using Dave's modified see-saw method. Bottom hose warm during process. Waited overnight to cool and did cool bleed - little or no bubbles. Went for a short drive 30mins (around town, up - down some steep hills). Got home and the radiator fan is running. The temp gauge was okay, at least it didn't go above 11o'clock. No strange noises. Heaters in the car hot. Should this happen (the fan running I mean)??? Is there still a problem? My hunch is yes, because I can't recall the fan running at all since I've had the van(6months). Also the original incident, before I did the bleed, was high temperature in the cab. Not so tonight, but it was persisting down - so ambient temp pretty low.

I'm really at a loss as what to do next. In the tests I have done (changing the thermostat, removing and examining the water pump) all components have been fine. The radiator seems not to be blocked (I did a test as described by Dave).

Would love to live near Allans but we're too far. Can anyone suggest a really good garage/mechanic in my area (Lanarkshire, Scotland) who has expert knowledge on Bongo problems of this nature, or suggest something else I could try?? Could it still be air in the system, for example?? I'm less interested in cost not - more interested in solving the problem.

I really need to get the van sorted asap - going to France at the end of June!!!

Any advice appreciated.

Hi Sly I'd expect the radiator fan to be running, the radiator can only work if air is passing over it and, around town, at low speed, the fan will come on. This doesn't indicate overheating, they are part of the normal cooling systen, not an emergency fall back. I think your bongo is probably fine, and what you really need is confidence. My advice would be to fit a Mason alarm. Apart from warning you of a problem it makes the guage work properly so you can see the temperature going up and down. They are only around £30 and fitted in under an hour.
Dave

[Slybacon]

Sounds like a plan Dave. I could very well be becoming paranoid and confidence is what I need.

I'll look into these options suggested by yourself and Haydn.

I think this is okay, but perhaps not: After doing the refilling of coolant on Wednesday night I left the van until the morning and checked the coolant level. After bleeding it was at full. In the morning it was still at full. I went for a short drive last night (as described earlier). I haven't driven her today at all. When I checked the level just now it was half way between min and full(max - whatever). I'm assuming that this could be fairly normal after the first run as I may not have expelled all the air and the drive did? It was cooler this evening too.

Any thoughts?

[Aethelric]

Hi Sly the coolant expands when it is hot and so the level will be higher. As the engine heats up, this expansion compresses the air in the header tank increasing the pressure. At the same time the air in the header tank heats up which also increases the pressure. And also the vapour pressure of the coolant increases the pressure too. All of these operating together pressurise the system thus raising the boiling point of the coolant.
Best to keep an eye on the coolant level at consistent temperatures - maybe in the morning before you set off?
Dave

[Slybacon]

Hi All.

All is now well with the van

I wanted to test things out before I reported back. Now, having done a 150 mile round trip, on motorway and a few days around town, temp gauge is fine, no fans running apart from what I would expect and I am a happy chap!

Meanwhile in the wonderful world of Bongo..........

On my way to work today, the van started to lose power - couldn't rev above 1500rpm. I've been using a fairly high veg mix (about 70veg:30derv) and was waiting for the fuel filter to gunge up with crud - and it decided to do it this morning!! After removing and replacing the filter I filled it up with neat derv, put a bit more derv in the tank (4.5l) waited a wee while and she started up - revving as normal. In the middle of it all I thought I had totally wrecked the van - but no, all is well.

Thanks to everyone for advice on overheating (which I reckon was really happening........) and changing the coolant. In the end I used the Mazda workshop method and felt quite reassured that all went well and there was no air in t'system.

Cheers

[mikeonb4c]

Excellent news Slybacon. I'm very timid with the veggie oil, only use about 6 litres per tank of diesel. 70% sounds very bold. I worry it may case glazing, binding of piston rings over time etc. especially if doing short runs with a cool engine. Given current price of veg oil I'm not sure its worth pushing it beyond 40% but maybe I'm being too cautious.