Overheating Issue

[erminrude]

Hi All
I finally bought my bongo last week (1998 2.5l Diesel) after about a year of looking and lurking.
Test drive was fine and she behaved. Drive home was fine. Temp was around 90 ish both times.
BUT .... we took her out for a short drive over the weekend and had an overheating problem. The dial went all the way up to (and past?) 100. Luckily we were able to pull over immediately and could hear the coolant bubbling. Coolant alarm did not sound and the coolant level in the header tank was fine.
Once things had calmed down, we got back on the road and drove home. Temp gauge would get up to about 95 ish and fan would kick in an it would drop down to around 40. We had hot air blowers on as well to help. This happened 2-3 times times.
I know just before I bought her that two new metal coolant pipes were fitted to get her through the MOT. The lady I bought her from clearly had no idea about Bongos and had driven her once or twice and lost her nerve. The garage that did the pipes were not Bongo specialists.
Sooooooo, my gut instinct is (only from what I have read on here and a FB forum) that there is an airlock in the coolant system and we will need to bleed it. I am guessing caused by the garage simply changing the pipes and topping up.
Does that sound feasible? Any other thoughts?
We are planning on bleeding the system (having watched the video) and going to go from there. Is there anything else we should be thinking about/watching for?
Sorry, I know nothing about mechanics other than what I have been reading about Bongos - not all of which I understand. Luckily my BF is mechanically trained, but doesn't know about bongos specifically.
TIA

[Bob]

What you say sounds very likely.

Sadly you may well have damaged the head as well, all too common if you continue to drive a Bongo when it's overheated.

definitely bleed it and see how you go, but it may well be worth doing a 'sniffer test' to establish if you have combustion gasses in the coolant, and a compression test would be worthwhile.

Fingers crossed for you.

[erminrude]

What you say sounds very likely.

Sadly you may well have damaged the head as well, all too common if you continue to drive a Bongo when it's overheated.

definitely bleed it and see how you go, but it may well be worth doing a 'sniffer test' to establish if you have combustion gasses in the coolant, and a compression test would be worthwhile.

Fingers crossed for you.

Thanks Bob. I have everything crossed. Not a very good start

[Thriller]

What temperature would be "too high" to run on?

This is for a petrol V6.

Alarm currently set at 92 but I am told that is too low for the alarm.

[g8dhe]

The V6 is a different beast altogether, I don't think there is enough evidence about temperatures when they fail. Myself I have had very high temperatures when the radiator top seal failed, but not offscale followed a couple of weeks ago by the top hose rupturing where I wasn't able to immediately stop (A13/N.Circular in London) the temperature hit fullscale for several minutes! Called the AA and we managed to get a tape around the rupture and despite a small leak I was able to get up to Yorkshire and call into Bongo Spares for an overhaul! Before continuing up to the Scottish Bash.

[mikeonb4c]

What temperature would be "too high" to run on?

This is for a petrol V6.

Alarm currently set at 92 but I am told that is too low for the alarm.

You'd be best starting a new discussion thread for this but in reply i'd say it depends very much on where the engine block sensors are located but 92 sounds too low. Something around 100-105 would seem more likely for the alarm but really its more a case of getting to know what figures are normal so you can investigate if/when they look abnormal. The most important temp is the engine core/coolant temp but that relies on the standard Mazda sensor and the standard temp gauge is heavily damped so it doesnt rise until overheating is occurring.