overheat while stationary, thermostat?

[nigelginny]

Hi guys, anyone help with this one, whilst sitting in traffic today my van overheated, not all the way to the red but about three quarters up not rising slowly but within about 10 seconds, also had water gushing out of the overflow pipe on the expansion tank and bubbling noise? but when we are moving the needle stays between eleven and twelve oclock, funny thing is it is erratic and seemed to sometimes be ok when we stopped.

Could this be the thermostat sticking, if so, years ago i ran a car i had without one, is this wise if only just till i can get hold of a replacement

cheers bongoers

[haydn callow]

Could be a stuck stat....justb change it....don't run without one fitted....no point.
If that dosn't work then come back.
Make sure you bleed it properly before you drive it again.
Did you lose much coolant and is it now a dirty brown ??

[nigelginny]

It is a rusty colour, ive checked out a few other threads and am now wondering if it might be a blocked rad, anyone help with where i might find the thermostat on the bongo and how easy is it to change?

[haydn callow]

The rusty colour is caused by the boiling coolant disturbing crud from low parts of the system.
You need to Back flush the system and check everthing...Loads of info in past topics

[nigelginny]

Thanks Haydn

[mikeonb4c]

If the pocket will wear it, I'd opt for a new thermostat and a new radiator. Good luck - keep us posted.

[missfixit70]

Are the fans kicking in?

[nigelginny]

yea the fan comes on when the needle hits around 12 oclock.

[Trouble at t'Mill]

Hi nigelginny.

As far as cooling is concerned, what's the main difference between when a car is moving and stationary? - when moving it has a 'ram' cooling effect; when stationary, it relies on electric fans.

So, the 'obvious' candidate here are the cooling fans. You say it comes on, but have you checked both? (I know there's two, but don't know the what the difference is between them... perhaps someone can inform me?!)

Ok, other things can cause similar symptoms - such as a partially blocked rad which might be adequate when cool air from driving is forced through it, but just ain't good enough when stationary and relying on a fan (tho' my gut feeling is that it should be enough)

Have you checked BOTH fans? (Can someone tell me the difference between them - what each does?!)

I don't see a sticking thermostat doing this, as surely it would allow overheating when driving too? The purpose of of thermostat are two-fold; one is to get the engine up to its ideal working temp as quickly as possible (so don't run an engine without one for any length of time...), and 2 is to regulate the temp by once there.

A 'stat would allow overheating if it's stuck closed, but surely it would also do this when driving along?

If you want to try tackling this yourself first, Nigel, I'd remove (and replace while you're at it) the stat, and remove and power-flush the rad. Give the bottom in particular some gentle knocks with a rubber mallet. Can you get flushing chemicals for car systems you add before dismantling (like you can for central heating systems)? Also, flush out the engine block and pipes (will work better without the stat in place, so remove stat, refit housing and flush.)

(And don't forget to refill properly - stating the 'bleedin' obvious there...)

[nfn]

I would guess that the thermostat being closed in town in winter would not lead to overheating.

With the Mason alarm fitted so that I can see the variation in temp, my bongo's coolant temp tends to drop in town if I'm doing lots of stop-start driving -- i.e., there's a tendency for the cooling system to over-cool it, even without the rad fan on.

It is more likely that your bongo's cooling system is blocked -- so I would go the new rad and flush route if I were you.

[mikeonb4c]

I have to say I'm sceptical about how well flushing chemicals actually work once the situation has gone beyond a certain point. If there is evidence of rustyness in the water, and you have had an overheating episode then - apart from checking that the twin radiator fans are working (I believe there are two, sat next to each other but not to be confused with the scavenger fan, which is separate and is there to cool the engine bay in extremis) - I would fit new thermostat (why not, they are cheap) and radiator. And since I was overhauling the coolant system, I might check and replace any iffy looking hoses. And of course I'd fit a low-high coolant alarm, and a Mason alarm for reassurance etc.

Depending on budget, I'd do some or all of those.

[nigelginny]

Thanks for all the suggestions guys, gonna whip the rad off today and flush it through, then flush the whole cooling system, im wondering if the antifreeze i put in last week was the correct type , ive heard that some when mixed with othrs can turn to jelly, maybe thats whats happened? it would explain some of the symptoms, i'll let you know what i discover.

[haydn callow]

Ah !! knowing now that you changed your coolant last week it seems a big coincidance that you overheated this week....I think you may have not bled it compleatly and left a airlock in there....thats now my bet.

[nigelginny]

I didnt replace all the coolant, just drained a few litres out and topped up with antifreeze, but i was chatting to my brother whos a trained as a mechanic, last night, i just asked if he had any spare antifreeze and he said he only had red? i said that i had put blue in mine which is when he explained about mixing two different colours.

[haydn callow]

Thats possible but ....you drained a "few liters" you then topped up with fresh...Did you go through the correct bleed method ? If you didn't then you will have probably introduced air into the system. Hence the problems. Did you bleed it useing the bleed pipe under the passenger seat and spending about 30 mins getting everything up to temp and the stat open ? If you didn't do this then thats your main problem. Most Blue anti freeze is universal so shouldn't matter if mixed...Though it's better to not do this just in case.