Underheating?!

[haydn callow]

The Bongo gauge fails in the closed position....See the current topic on cooling system diagram.
What could cause it to jam opem other than a large forign object coming from the bottom of the rad and sticking in there ??? Possible but so unlikely.
The Stat does not even begine to open untill the stat reaches at least 82 C...(a stat in good condition) (a stat in poor condition will open at a higher temp)
The gauge starts to move when the gauge sensor (coolant around it) reaches approx 50C and is at 11 o'clock at 60C ,,That stat is Not yet open.(the cylinder head temp has to be a lot higher than 82C before the stat reaches 82C)
If you read the topic on the system diagram this is all covered..
What other vehicles do and how they react is another story and not really relevant to the Bongo.

[haydn callow]

Don't forget Mike...the Bongo gauge has a dead area...It remains on 11 o'clock from about 55C to 110C ....useless......unless you have a Mason fitted or the Mod I suggest (costs 5p)
The chance of spotting your gauge move up to HOT from the 11 o'clock position before you get to critical temps is not good.......This is why peeps fit either a Mason or TM-2 or some other temp gauge


2) When I changed my Bongos temp gauge, time to move from COLD stop reduced from 10 mins to 5 mins

Do you mean temp gauge or stat....??

[curlew]

OK everyone - back to mememememememememememem!!!!!!!!!!

Garage man says it's a faulty thermostat and it's fine to drive. Opinions, oh knowledgeable people?

[haydn callow]

Is the garage man happy to recover you and fix it if it all goes wrong ?? if he o.k's it then go for it...probably o.k. but watch that gauge...if it passes 12 o'clock stop and ring him

[Doone]

There have been a few reports on the forum of bongos being driven with faulty thermostats. This garage knows the history of your bongo, are you driving to them to get it changed? If they've agreed that, then they seem to be taking responsibilty if anything goes wrong. Or play safe and get it recovered, then you'll have no worries.

[missfixit70]

If I had any doubts about my stat I wouldn't drive it, it is the main control point in the cooling system (if you read the thread I linked to). Worst case - you could end up with a disastrous overheat. Get the garage to sort transport, or if you've got cover, get it recovered to the garage. Just my opinion.

[mikeonb4c]

Don'forget Mike...the Bongo gauge has a dead area...It remains on 11o'clock from about 55C to 110C ....useless......unless you have a Mason fitted or the Mod I suggest (costs 5p)

Yup, appreciate that. I wonder though if most cars of that vintage aren't the same and thinking about it, it's easy to see why. As far as the manufacturer is concerned, the user only needs to know that their engine has warmed up OK, and that it isn't overheating. The gauge moving around the centre band may only cause them to worry about the natural fluctuations that can occur and that are broadly speaking 'normal' (only us obsessive Bongo type geeks want to watch its every movement, and may know how to interpret them ).

All this brings back a memory of my older cars, where I'm sure I can recall seeing the needle position varying more than it did on the Sunny or does on the Bongo. I wonder if at some point the idea crept in that it would look great to users if their engine temp appeared rock steady even if in fact it wasn't, as crude old thermostat technology was being used. Really, the effort would be better directed to keeping these engines running at the optimum temp but I assume generally that is not done. Does anyone know if more intelligent engine temp maintenance devices are in use these days (other than on racing cars)?

PS - curlew. Maybe Haydns concern is you have an airlock in the system due to incomplete bleeding. If so, caution would seem sensible. can the garage reassure you that is not the case? It seems odd that the opportunity to test and/or change the thermostat was not undertaken during ht erebuild. The even more interesting possiblity arises that the overheating was caused by a thermostat that failed to open. If the temp sensor was downstream of that - or possibly even if upstream but next to it - it may well register cold even if core temp is hot, as there is no flow around the engine. I'd always assumed the small bleed hole in the thermostat was to allow a little water to pass and thus warm it, but this may be insufficient in volume to reliably immerse and warm the temp sender in hot water. All the above is speculation by a non-mechanic (moi!) so may be off the mark

[apole]

Hi again,

I'm confused. If a stat fails does it allow or not allow coolant to flow through the radiator? I always thought if one failed your car would tend to run too cold as the coolant would always go round the radiator.

Andy

[haydn callow]

Mike.read the long topic on the coolant diagram.....it is all in there....There is plenty of flow around the engine even even the stat is shut (most of the time)....the bypass system takes care of the cooling except when things get stressed a bit. then the stat opens and chips in....The springs on the stat are so strong you cannot force one open....needs heat

[missfixit70]

Read the coolant thread I linked to, should help explain

[haydn callow]

If the stat fails it does NOT allow coolant to pass through the Rad

[missfixit70]

If the stat fails it does NOT allow coolant to pass through the Rad

Although it is always circulating through the top part via the expansion tank, but this is all being discussed on the other coolant thread

[apole]

Thanks guys, good info to know. I did read the thread but it is quite long.

I do have a reason for asking in that I've noticed my car recently runs a bit hotter sometimes than usual but does come down, I put it down to a lazy thermostat and as I need to change a coolant pipe next week I ordered a new stat to fit whilst I was at it.

Thanks again.

Andy

[haydn callow]

If the stat fails it does NOT allow coolant to pass through the Rad

Although it is always circualting through the top part via the expansion tank, but this is all being disscussed on the other coolant thread

O.K...O.K....but you know what I mean

[mikeonb4c]

If the stat fails it does NOT allow coolant to pass through the Rad

You are referring to Bongos I presume, not all cars, and by fail you mean 'fails to open'.

I've read quite enough on BF about Bongo cooling systems on here - more than enough to make my head spin or, to be more precise, to leave me thinking there are a lot of (self elected?) experts, all of whom think they are right and yet who have struggled (wht?) to agree on how the Bongo coolant system works (I recall a diagram showing the coolant system that some people were not happy to agree as being correct - was TGP one of them - it looks like an official diagram but the red and blue bits of the circuit are a BF addition). So I'm outa that debate. I tend not to think I am right, but I do try and use what little understanding I gather, in order to guide me. So far, as in (1) and (2) in my earlier post, the results have suggested, most gratifyingly, that I have been right in the actions I took (or insisted obstinate others took ).