Another Coolant Alarm Issue

[Mark Elvin]

My coolant/temp alarm has started behaving weirdly.

If I stop for a while, then restart the van, the temp alarm sounds for at most a second before dropping back to a normal temp reading.....

[haydn callow]

If you have set the temp alarm a couple of degrees above your normal running temp, when you stop the engine the heat builds up and may add as much as 10 degrees, if you then restart within about 10/15 mins the temp will still be high and set off the alarm, it will very quickly cool down as the coolant recirculates.

[teenmal]

Mark, as a matter of interest does the display show 85 when this happens.

[Simon Jones]

You don't say what alarm is fitted, but it's normal (as I recall) with the TM2 / TM4 to display the value the alarm is set to when first powered up so it will appear to read high and then drop to correct reading.

[Mark Elvin]

If you have set the temp alarm a couple of degrees above your normal running temp, when you stop the engine the heat builds up and may add as much as 10 degrees, if you then restart within about 10/15 mins the temp will still be high and set off the alarm, it will very quickly cool down as the coolant recirculates.

It's called heat soak. 20years designing race cars (including cooling systems)has taught me that much.

My normal running temp is around 86c, the alarm is set at 106c.

If it were reading the correct temp of the cylinder head it would not drop in about 1second, it would be a gradual decrease, not the "HOT" warning, then immediately (& I mean immediately) 85-86c (or whatever the real temp is).

[Simon Jones]

What reading is displayed when the alarm sounds after restarting the engine and where is the power supply for the alarm taken from?

[Mark Elvin]

What reading is displayed when the alarm sounds after restarting the engine and where is the power supply for the alarm taken from?

12v taken from supply switched by ignition, reading simply says "hot", then after 1second or so returns to correct temp.

[Simon Jones]

Not one of Haydn's alarms by the sound of it.

[Mark Elvin]

Not one of Haydn's alarms by the sound of it.

Yes it is. I bought it shortly after buying the Bongo.

Non stop low coolant alerts, requiring screws being replaced on a monthly basis, now this.

Have to say I may be in a minority, but I've found it a non stop source of hassle.

[haydn callow]

Send it back and we will replace it for you......then we will test the returned one and I can say with a high degree of certainty that it will check out as good.

[haydn callow]

If you are changing the screws after all this time you have a problem in the cooling system.....are you using red long life coolant.?

[Mark Elvin]

If you are changing the screws after all this time you have a problem in the cooling system.....are you using red long life coolant.?

Yes it is the Red coolant. What sort of problems with the cooling system would you suggest then? It's recently been given a clean bill of health by ADS

[Mark Elvin]

If you are changing the screws after all this time you have a problem in the cooling system.....are you using red long life coolant.?

Something is not right, either with my Bongo or the alarm. I was hoping to be able to sort what it is if it is my van.

What issues would cause these symptoms if it's not a faulty alarm?

[haydn callow]

Red coolant causes problems, but only for a couple of weeks after the coolant is put in. After that and a clean screw it is fine. Dirty coolant can also cause problems as can a gremlin in the electrical system.
Generally, these coolant alarms do not fail and if one did it would not work at all. We have had 3 or 4 returned over the years with your symptoms and they have all checked out o.k. And been refitted to another vehicle with no problems. The temp alarm side of things could play up but very rare, perhaps 2 out of many hundreds sold and the alarms themselves were all o.k. But the sensor cable had been damaged.
If you have a voltmeter measure the voltage between coolant alarm sensor screw and Earth with the ign switched on and again with engine running....and report back.

[haydn callow]

We used to supply lots of alarms to ADS,(years ago) then they changed from using blue to red comma 5 year coolant.....then the problems started with the alarms.......that particular coolant seems to coat the screws more than most....it still stops coating the screw after a few weeks but they decided it was to much hassel. They stopped fitting the alarms and in fact discourage them being fitted.......all I can say is...almost all of the main Bongo dealers including the 3 biggest in the country no longer sell a bongo without a low coolant alarm fitted and have listened to our advice and used blue 2 year coolant....it's better to have a good quality low coolant alarm fitted than not fit one and use the red coolant.......having said that loads of Bongos do use red coolant and after a couple of weeks and a clean screw have no further problems.
I don't know what your problem is with the temp alarm, send it back and we will sort it for you.
You won't get better after sales from anyone. We will always sort it.....we live by our reputation....6000 plus Bongo owners cannot be wrong. And 20.000 pluse vehicals worldwide.