running hot; when should cooling fan be running?

[gasace]

Hi everyone, I hope someone can help. After reading all the post on here about cooling problems, I fitted a low coolant alarm and did the temperature gauge mod. I found the bongo running hot so I changed the resistor for 110 ohms and the gauge was still at the upper end. Not sure if the sender/gauge was correct, and to give an alarm if overheating I have just fitted a second temperature gauge/alarm (the one that fits in place of a switch blank) this proved that it is the bongo at fault not the gauge. I am going to replace the thermostat and coolant. If this does not do the job then it will be a new rad. This is the bit I need help with has anyone flushed the cooling system with chemicals? I am a heating engineer, when we have a clogged heating system we do a chemical clean. The materials and temperature range on the bongo and a heating system are very similar. Can anyone suggest a cleaner or any reason why I should not use a mild heating cleaner (Fernox F3) Also the cooling fans, it looks like there are 2 is that right? When I got back after a run the gauge was reading over 100 degrees but both fans were not running, when should they run? do they both run together?

Please help if you can, thanks gasace

[Northern Bongolow]

hi firstly please read the thread on here now, titled themostate pictures,it shows the stat and the issues with the port at the top of the housing,this imo must be clean.

i see no reason why a cleaner like you use domesticaly cannot be used on a bongo.
the brass ends of both the temp sender (front offside of cylinder head)single wire to it,and fan switch(rear offside of engine block above starter motor)twin wire,both suffer from tarnishing,and ideally should be replaced with GEN MAZDA PARTS,as the copies vary in their accuracy.the fan switch usually fractures at its joint of plastic end to metal probe.
please also use a gen mazda stat also.

please make sure you bleed the system properly,as per the fact sheet.at the risk of being patronizing you may think you can do it ,which you probably can,but please make sure its done correctly.or it will cost you dear.

ps if you do a chemical flush, please make sure it is well flushed out after,and remove the rear heater pipes and flush out this matrix,as all the crud settles in this low point!!watch the plastic stubs on this as they can break off.

a quick run through the system goes as follows.
get motor temp up to working temp.
bottom hose hot to touch,not warm.(stat open)
carry on reving and fans come on just before the line at hot,they come on in stages,so please check carefully.temp should then dump down within 5 seconds approx.

your input on this is required as you are used to working in this feild so can you please feed back.

as i see your problem,the following should be done(just my oppinion)
new mazda stat. make sure the port is cleen.
new fan switch.
new temp sender.
new coolant.

please let us all know how you get on, as there seems to be a debate about this very thing at the moment.
regards ady

[widdowson2008]

Hi everyone, I hope someone can help. After reading all the post on here about cooling problems, I fitted a low coolant alarm and did the temperature gauge mod. I found the bongo running hot so I changed the resistor for 110 ohms and the gauge was still at the upper end. Not sure if the sender/gauge was correct, and to give an alarm if overheating I have just fitted a second temperature gauge/alarm (the one that fits in place of a switch blank) this proved that it is the bongo at fault not the gauge. I am going to replace the thermostat and coolant. If this does not do the job then it will be a new rad. This is the bit I need help with has anyone flushed the cooling system with chemicals? I am a heating engineer, when we have a clogged heating system we do a chemical clean. The materials and temperature range on the bongo and a heating system are very similar. Can anyone suggest a cleaner or any reason why I should not use a mild heating cleaner (Fernox F3) Also the cooling fans, it looks like there are 2 is that right? When I got back after a run the gauge was reading over 100 degrees but both fans were not running, when should they run? do they both run together?

Please help if you can, thanks gasace

There are indeed2 fans. Nearside is 5 blade - Offside is 7 blade. My fans operate when the aircon is switched on (I believe this is normal).
Not much help otherwise - sorry.

You're tooooooooooo fast Ady - beat me again.

[haydn callow]

You say the (( i-alert )) temp gauge read 100C plus when you stopped !! what is more important is what it was reading before you stopped as the temp can rise by as much as 10C after stopping.....
From you description of what the modified gauge is reading it does sound as though you are running a little on the hot side and you are doing the right thing by invesigating....However things may not be so bad as you suspect and if you hadn't fitted any mods/gauges you would be non the wiser.
In this weather and during a good run and if the (( i-alert )) sensor is where suggested (back of cylinder head) 95C would not be out of the ordinary.
Having said all that the maintainance suggestions listed in above posts can only be a good thing and help the long term prognosis.
Prevention is always better than the cure.

[gasace]

The temperature when running uphill but not booting it was a lot higher (not fully got to grips with the temp. over 100)
but when I stopped I put the heater of full and let the engine run before I shut it down. I bolted the i-alert sensor to the middle of the cyl head. I think the readings are OK as the mazda gauge is showing hot as well

You say the (( i-alert )) temp gauge read 100C plus when you stopped !! what is more important is what it was reading before you stopped as the temp can rise by as much as 10C after stopping.....
From you description of what the modified gauge is reading it does sound as though you are running a little on the hot side and you are doing the right thing by invesigating....However things may not be so bad as you suspect and if you hadn't fitted any mods/gauges you would be non the wiser.
In this weather and during a good run and if the (( i-alert )) sensor is where suggested (back of cylinder head) 95C would not be out of the ordinary.
Having said all that the maintainance suggestions listed in above posts can only be a good thing and help the long term prognosis.
Prevention is always better than the cure.

[helen&tony]

Hi
What side of the head?...sounds like it might be passenger side. Photos , please, if poss.
A good place to try is to tape the sensor on the outside of the main exit pipe from the cylinder head, using some insulating tape. It will take a little longer for the temperature to read, as the hose itself has to warm. You are then reading the water temp at the hottest part of the system that is accessible . Normal running will be in the low to mid 90s
Once you have found the water temperature is O.K. you can replace the sensor anywhere you want to read....you then only look for increases in temperature above your normal running temperature FOR THE PLACE YOU HAVE INSTALLED IT.
Cheers
Helen

[haydn callow]

Which side of the cylinder head ???......I'm afraid that unless you bolt it where suggested in the instructions (photo supplied by me) the readings will mean nothing to anyone else....If you have the sensor on the passenger side of the cylinder (exaust side) I would expect the readings to be even higher...
I.m afraid I cannot be of much help unless you move that sensor.....

[haydn callow]

To quick for me Helen

[mikeonb4c]

Do I recall some warnings on here recently about ensuring the chemical cleaner is one that does not attack aluminium or somesuch?

[Scott]

Spookily enough, yesterdat I took the van for its MOT and a little jaunt, the iAlert (sensor in recommended position) was sitting around the 89/91 mark and the modified temp guage was sitting a little bit higher than normal (put this down to weather).

My 100 ohm modified gauge ranges around the 11 up 12 o'clock on normal use and goes up a bit uphill etc

Got back home and thought I would test the iAlert alarm knowing that the engine temp would rise when I shut her down. switched the aircon off and turned off the engine so I could watch the alarm rise, my engine fan cut in at 94 and the alarm went off at 95.

It all worked but not sure if these figures are correct'ish but it might be a help to you

[haydn callow]

Unless the sensors are all in the same position the readings mean very little in relation to each other.

[missfixit70]

Spookily enough, yesterdat I took the van for its MOT and a little jaunt, the iAlert (sensor in recommended position) was sitting around the 89/91 mark and the modified temp guage was sitting a little bit higher than normal (put this down to weather).

My 100 ohm modified gauge ranges around the 11 up 12 o'clock on normal use and goes up a bit uphill etc

Got back home and thought I would test the iAlert alarm knowing that the engine temp would rise when I shut her down. switched the aircon off and turned off the engine so I could watch the alarm rise, my engine fan cut in at 94 and the alarm went off at 95.

It all worked but not sure if these figures are correct'ish but it might be a help to you

My fan/s cut in at 94 (when it's running right) measuring from top hose outlet, takes it down to around 84-85, but unless the stat is working properly, even if the fans kick in, there won't be enough coolant flowing through it for the fans to do anything.
I used Holts 2 part rad flush & as Ady says make sure it's thoroughly flushed out, that means bleeding it up to & beyond stat opening temp to make sure everything gets flushed several times. I did mine with the stat out so everything was open.

[Northern Bongolow]

when you flush it out drop the rear heater pipes off,as the heavy solids settle here at the lowest point,flush the matrix out to,

[missfixit70]

Agree with that, get the hosepipe in everywhere you can once it's cooled & flush it through, engine, rad, bottom hoses, heaters.

[Scott]

My fan/s cut in at 94 (when it's running right) measuring from top hose outlet, takes it down to around 84-85, but unless the stat is working properly, even if the fans kick in, there won't be enough coolant flowing through it for the fans to do anything.
I used Holts 2 part rad flush & as Ady says make sure it's thoroughly flushed out, that means bleeding it up to & beyond stat opening temp to make sure everythngi gets flushed several times. I did mine with the stat out so everything was open.

right that makes sense, without removing the stat and using a saucepan is there an easy way to test the stat is opening correctly? I don't really want to start messing around with an already temperamental coolant system and add a problem where there wasn't one to start with

It might be a safer bet for me to put it into a bongo garage and have them drain, flush and refill the system and whilst it's there get a pukka Mazda stat fitted too?