cooling fans

[steady1946]

We have just returned from a holiday in the Peak District.
While there we got stuck in traffic on the A57 near Stockport/Manchester.The Bongo engine was getting quite warm and got up to 3 quarters when my Mason alarm started chirping,The cooling fans did not cut in at all.When I returned to the campsite I called out the breakdown people.He tested all the plugs to the fans and the fuses and could niot find anything wrong with them.He suggested when it came to going home I should have my air-con on which would operate the fans.
When I got home I took Bongo to my local Bongo garage(fury approved).He said it was probably the 2 sensors on the engine.I left the Bongo with him to repair.He phoned me to say that he had changed the sensor ,but the fans would not cut in at the right temperature.He phoned round a few other Bongo garages and they said it maybe the Mason alarm causing the trouble.
Could this be right?

Ed

[missfixit70]

Nope, the Mason alarm has nowt to do with the fans, it takes its feed from the sensor on the top hose which does not affect the fans, the fans take their feed via the ecu from the 2 pin sensor above the starter motor on the drivers side of the engine. How are they measuring the fan cut in temp? Do the fans cut in when you pull the connector off the 2 pin sensor?
Maybe your Mason alarm is set a bit low for you & the temps hadn't reached the point the fans should cut in? if the temp rose to 3/4 it probably hadn't reached switching point, did it stay there or go down? What actually hapened in detail? sounds like a possible case of bongo paranoia to me

[steady1946]

Hi
The Bongo garage pulled the connector off and the fans started working.
The breakdown man left the Bongo running to try to reach a temperature so the fans cut in,but it got up to near the 'H' and still no joy he did not want to leave it to get too hot so stopped the engine.The Bongo garage are going to disconnect the Mason alarm to see if it is this. The alarm is set at No 4 where there is a blue mark on it.
Ed

[missfixit70]

Mason alarm has nothing to do with it it just resensitises the temp gauge, it is seperate from the ecu, which controls the fans, did they actually measure temperatures? did the garage run it right up to temp after they fitted new sensors? turn the Mason up a touch if it's going off too early, most seem to have it set around 4.5. I'd say I'm surprised at a bongo friendly garage not knowing how the temperature control/fan switching works, but it seems a lot don't know as much as we'd hope.

[steady1946]

Hi
When should the fans cut in to cool the engine.Surely it should not be up to the H. Would turning the Mason up solve my problem?
Ed

[missfixit70]

Turning up the Mason will just raise the point at which the alarm sounds, it has no effect on the fans, it just seemed to me that maybe you had expectations that the fans should cut in with the mason alarm?
Did the Garage run the engine up to temp to check if the fans cut in after they fitted a new sensor?, mine were cutting in when it was around 93 degrees on the top hose near the temp sensor for the temp gauge, which was just past this point, but each bongo is slightly different depending on the condition of the system etc. Fans should cut in before it goes off scale, but you didn't say if the garage tested up to this point?



Difficult to help with piecemeal details

[steady1946]

My gauge went past that point and still did not cut in the fans.I would have thought the garage would have run it to see if they did cut in . He said he even tried testing them in boiling water to see if the fans cut in? I have used the garage before to do my yearly service with no probs.
Ed

[missfixit70]

First thing is to measure actual temperatures, at the top hose, if the fans haven't switched in by 95 degrees on the top hose, then it needs further investigation IMO.
Worth checking the sensor is working ok then, especially if it's not a genuine Mazda one, at 20 degrees it should have a resistance of 2.3-2.6 kilo ohms, at 80 degrees it should have a resistance of 0.29 - 0.34 kilo ohms. Check all the connections are clean & tight.
Worth checking the ecu voltages too, terminal 2N, with ignition on, coolant at 20 degrees should be @2.1v, at 80 degrees should [email protected].

Did they bleed it properly after fitting new sensors?
Where does your gauge normally sit?

[steady1946]

I did ask him if there was any air in the system and he said he tested that with the bleed pipe.He has bled a Bongo before,he changed my water pump last year so he knows about Bongo bleeding.My gauge used to sit between 10 & 11 o'clock.
I will take on board what you have said and relay this to my garage. Thanks for your advice.
Ed

[missfixit70]

If it's not had a new thermostat recently, it'd be worth fitting a new genuine Mazda one. If it doesn't open fully before the top hose gets to @90 degrees, then even if the fans do cut in, they won't bring the temp down as the recirc inlet into the top of the stat will still be open, this needs to close (which is illustrated here - http://www.igmaynard.co.uk/bongo/forum/ ... 57#p428257 ) to push the majority of the coolant around the rad so it can then be cooled by airflow due to the vehicles motion, or by the fan/s when slow moving/stationary. Also check the rad is doing it's job.

[missfixit70]

Slight ammendment to the last post

If it's not had a new thermostat recently, it'd be worth fitting a new genuine Mazda one. If it doesn't open fully before the top hose gets to @90 degrees, then even if the fans do cut in, they will struggle to bring the temp down at the top end as the recirc inlet into the top of the stat will still be open, this needs to close (which is illustrated here - http://www.igmaynard.co.uk/bongo/forum/ ... 57#p428257 ) to push the majority of the coolant around the rad so it can then be cooled by airflow due to the vehicles motion, or by the fan/s when slow moving/stationary. Also check the rad is doing it's job properly.

The cooling system is more complex than that, depending on the speed/conditions/load etc, but I was just trying to illustrate why a new stat may be a good idea

[Northern Bongolow]

all kirsty says above is correct,the crux of this in my opinion is,i think you will find that the new sensor that your garage have fitted will be a copy one, not a gen mazda one.these tend to read HIGHER than they should,this will make you think it is hotter than it actually is,and you panic that the fans are not coming on when aproaching HOT

as kirsty is saying you need to find out what the true temps are.or fit a gen mazda temp switch and gen mazda fan switch,

a test you could do on the drive yourself,if you dont bottle out is,
run the motor for about ten minutes to get up to temp,rev it for a while until you get the stat to open, 82 degrees,THE BOTTOM HOSE SHOULD BE TO HOT TO HOLD FOR MORE THAN 10 SECONDS,the temp gauge should be if eveything is normal,at about where kirstys is in the picture above,carry on running/reving until the fans come on just at the line BEFORE the H
if this does not happen at the above temps/gauge readings,something is amiss,
then refer to the above,
WARNING-- if in doubt do not do this,seek advice from your bongo garage.IF THERE IS A FAULT IN YOUR SYSTEM OR FANS YOU COULD DAMAGE YOUR ENGINE

[mikexgough]

the fans come on just at the line BEFORE the H if this does not happen at the above temps/gauge readings,something is amiss

I agree, with the ECU parameters set at a fixed (IMHO a too high) temperature the Fans will kick in at the late stage, which for a Mason modified gauge, would be really scarey....... you would need to hold your nerve and wait for Northern Bongolow's described gauge trigger point to test the fan operation when in service.
This shows the main reason why that Mazda damped the gauge down so severely, owners would have concerns and being going to Mazda dealerships with the "issue"..... Plus of course with an efficient Bongo cooling system, the fans will rarely run anyway.

Many folks run cars, not just Bongos, with the air con deployed and as a consequence never have issues with cooling, but then their fuel consumption suffers as the engine takes longer to get to the normal operating temperature. I guess in reality that during the summer & air con times, the job of the cooling fans to cool the engine is over ridden by the air con running.

[g8dhe]

Many folks run cars, not just Bongos, with the air con deployed and as a consequence never have issues with cooling, but then their fuel consumption suffers as the engine takes longer to get to the normal operating temperature. I guess in reality that during the summer & air con times, the job of the cooling fans to cool the engine is over ridden by the air con running.

Surely if you turn the Air Con on the engine will have to do MORE work as it is now turning the compressor pump, and thus the engine will get hotter quicker? The refrigerant doesn't get used to cool the engine only the passengers. So yes mpg will be affected but the engine is using more fuel for the very reason that it needs to do more work. But I can't see how it can help keep the engine cool, in fact the opposite.

Or am I missing something here ?

[missfixit70]

If the ac is switched on, the rad fan/s will come on when necessary (not sure if they still do when the vehicle is in motion & the forward motion takes care of the cooling, if this is so, then how?), thus as soon as the stat opens & allows any coolant through the rad, the fans will always be spinning & at low speeds/stationary will help to keep the temp down without the system having to get up to fan switch temp. You are right in that the compressor/fans will effectively be putting more load on the engine, but as the fans will be cooling the rad it won't show as elevated running tempsat low speeds/stationary.