overheating?

[Bobtail]

on the way to work this evening noticed the temp gauge getting
very high so turned heater on full blast and heating on full temp
and there was only cold air coming out
so pulled over and released water filler cap and water bubbled out
and i could hear loud bubbling sounds from header tank
when it had finished bubbling removed top and filled up water
started engine and refilled water again
put cap back on and started off again 2 miles down road the temp
gauge started to rise again pulled over again and now the funny thing left
in ticking over to check under bonnet and temp gauge started to go down
left it for ten mins and all seemed ok started off again and temp gauge
started to rise then fell back to normal running temp and heater
started to blow hot air  
any ideas?

head gasket?
thermostat?
air lock?

help very worried :-k

[muddysteve]

sounds like an air lock if all is well now, could have had an airlock in the heater matrix

Steve

[bilge rat]

as said before sounds very much like an air lock ! ,the concerning thing is how did it get there ,have you had any of the coolant drained down recently. iff not could be cause of head gasket gone between cylinder and water jacket, ive heard though this is un common as 300s normally go on no4 at the back of the block. dont know weather it works on deisels but you could take the water pump belt off ,brim the header tank making sure no air in system first and run for about 10 to 15 seconds (you dont want it to hot)see iff you get a stream of air bubbles ,hopefully you wont ! .iff ya do good chance of gasket trouble, hope this may be some help...

[Niel]

on the way to work this evening noticed the temp gauge getting
very high so turned heater on full blast and heating on full temp
and there was only cold air coming out


head gasket?
thermostat?
air lock?

help very worried :-k

Check the plug in the rad hasn't split, BTDT.

RS sell some nice chrome plated brass ones that fit ;-)

Niel.

[Mace]

The bubbling could be the sound of water boiling coz it's got too hot. They then get stuck at a high point i.e the heater matrix. Releasing the cap releases the pressure and releases the air. I would have thought an air lock alone would have presented itself earlier than this. That said, you've just had the cam belt done so maybe the air got in then.

You may have a blockage in the coolant system, radiator is a good point or a partialy seized water pump. This would have caused the orginal rise in temp. The pressure build up could have blown it clear so things are now as normal.

Check your oil filler cap for water residue and keep and eye on the coolant level. If all seems well in a couple of days it's probably past, if not it's something serious.

[Range Rover Blues]

The pressure in the system stops the boiling, when you take the cap off the pressure goes and the water boils, that's why it's so dangerous to take the cap off a hot engine.
It does sound like an air lock but where it's from I don't know (assuming it's a deisel).  I would point out that on a V8 there is a special filler on top of the engine becuase of this problem, you need to fill it very fast through the little plug to force air out of the system.  I also bleed mine periodically from this plug, although no air seems to collect there anymore.

[Mace]

The pressure in the system stops the boiling, when you take the cap off the pressure goes and the water boils, that's why it's so dangerous to take the cap off a hot engine.

Thanks for that Andrew, I stand corrected :-)

[Bobtail]

it does seem to have been an air lock as mace said had cam
belt done last week so may be down to that (they have to take off
water pump on 300tdi)
its been fine today only time will tell *fingers crossed*

thanks for the help will let you know if it does it again

jim

[Range Rover Blues]

Did it get filled with anti freeze mix?

I ask because tap water does contain an amount of absorbed air or oxygen (not sure which but it's what fish breath) so air locks can occur in a system that's just been filled up, especially if the water got aerated as it was poured at any time.  The air/oxegen whatever slowly releases as the coolant is heated and would normaly just vent into the header or at the top of a hose.  This can cause an airlock which is why I used to bleed my coolant from the filler (see above).

If it doesn't do it again then problem solved (even if happens but not as badly).

[Bobtail]

well its not fixed going to take it to doctors tomorrow

*fingers crossed* it will not be expensive :-({|=

[Range Rover Blues]

There's suddenly a lot of this overheating going on.

[Bobtail]

well i removed the thermostat yesterday and checked it was moving
it only moved about 5mm to 8mm in boiling water from the kettle
is this norm or not?
left it out and came to work today temp gauge a little below norm
which was to be expected but heater working and no overheating
so going to get new thermostat and suck 'n' see or anyone got any other ideas?