cooling system problems

[sarahautobus]

can anyone please help me i have a 2.1 fuel injected caravelle which is overheating , ive replaced all the sensors,bled the air out numerous times . the red light now goes out after a few seconds and the guage needle doesnt go up enough to say that its overheating but the liquid is boiling in the header tank i have to keep stopping and letting her cool down which is really anoying . has anyone had such a problem or does anyone know what the problem might be please help me ?

[jason k]

have you changed the thermostat?

if so did you use a genuine vw one?

if you used a gsf one they are pants.

[sarahautobus]

yes i did change the thermostsat or the guy in the garage did but hes cut out the middle and for some reason he only put the middle sealing ring piece back in as i discovered the other day ,i also think it may be from gsf.

[R0B]

that suggests to me the tank is not full to the brim.it should be

but the liquid is boiling in the header tank

[Ian Hulley]

that suggests to me the tank is not full to the brim.

Suggests to me you need a new garage. Welcome to the club btw

Ian

[sarahautobus]

the front of the van has been lowered about 50mm im guessing would that make any difference .so the header tank should be full to the brim at all times .

[R0B]

from cold,the tank should be full to the brim...

[sarahautobus]

ive just filled the header tank to the brim and rebled the system ,had it running for quite a while and the temp guage hardly registered any move ment which isnt right i know.

[Grun]

yes i did change the thermostsat or the guy in the garage did but hes cut out the middle and for some reason he only put the middle sealing ring piece back in as i discovered the other day ,i also think it may be from gsf.

have you changed the thermostat?

if so did you use a genuine vw one?

if you used a gsf one they are pants.

Do get a genuine thermostat properly fitted first, and then see if temperature gauge problems are still there.

Simon Baxter at Brickwerks does a thermostat.
http://www.brickwerks.co.uk/index.php?p ... t&Itemid=6" onclick="window.open(this.href);return false;

Unlike your average engine where removing (or in the case of your 'Guy in the garage' altering) the thermostat leads to increased flow through the radiator. On the waterboxer having no thermostat (or an altered one) will only tend to make the coolant recirculate through the engine and not the radiator.



With a cold engine the coolant flow from the right hand cylinder head travels through the pink coloured pipe across to the thermostat housing where it joins the flow from the left hand cylinder head and returns to the coolant pump.
With a warm engine when the thermostat operates the flow is reversed and travels from the left cylinder head across to join the flow from the right cylinder head and onward to the radiator returning via the thermostat housing to the coolant pump.

Mike

[ghost123uk]

yes i did change the thermostsat or the guy in the garage did but hes cut out the middle and for some reason he only put the middle sealing ring piece back in

I hope he did not charge for this "diss-service" !!!!!!!!!!!!!!!!!!

Do not go back there and tell as many folks as you can not to go there either !!

As has been said, fit a proper VW stat then follow the bleeding instructions, that are in our "wiki" section TO THE LETTER. Boiling like you describe is usually big air locks in the system.


(p.s. "follow the bleeding instructions" = that reads nice doesn't it )
.

[Red Westie]

If you think of it like this: There are two bodies of coolant....the smaller amount in the engine and the larger amount in the radiator and front to rear pipes. The thermostat simply seperates the two bodies of coolant until the temperature of the engine coolant rises sufficienty (usually around 82 degrees C) to cause the thermostat to open. At this point the themostat can open/close several times, mixing the cold coolant from the radiator with the hot water from the engine until all the coolant reaches a similar temperature. The reason for the thermostat is to ensure the engine warms up quickly and gets to normal operating temperature as soon as possible. Taking the thermostat out or removing it's centre means the engine is having to warm the whole 'volume' of coolant straight away and in fact this may mean the engine never reaches it's normal running temperature on short journeys or cold days. With the thermostat removed the engine will remain on 'choke' for longer (the rich mixture that a cold engine needs) and so the fuel consumption will drop dramatically. Running on 'Choke' for long periods may also lead to the engine oil being thinned by petrol contamination getting past the piston rings not to mention high pollutants and rough running.
All in all you first priority needs to be to replace the thermostat (genuine VW prefered), properly bleed the system. The fact that you have seen the coolant boiling may indicate that the pressure cap is faulty (the Blue Darlek type cap on the main full coolant bottle) Ask yourself a question: Were the hoses completely solid and under high pressure when you experienced the coolant boiling? if they weren't???? then it points clearly to a pressure cap fault. I would suggest that you change the pressure cap at the same time as the thermostat purely as a precaution. Once you have done this then you can check for correct operation of the radiators thermo fan switch, run the engine to warm (the fan should kick in and operate when the needle on the temp guage goes a little over half way) Some are two staged fans. If the fan doesn't click in I suggest you may have a thermo switch fault (you can check this by pulling off the plug to the thermo switch and bridging the contacts (not sure which ones) if the fan works and the radiator temperature and gauge indicates say 2 thirds leave connected so you can see the gauge dropping again indicating that the thermo switch needs changing. Don't allow the engine to over heat.
Martin

[sarahautobus]

thanks guys for all your help i have changed all of the sensors throughout the cooling system and the one on the rad,im just going to order some parts and see if i can sort it out .i did find one part of the vacuum pipe split so that is being replaced as well . does having the front end lowered make any diference to the cooling system ,am thinking of levelling her out just in case anyway.

[ghost123uk]

does having the front end lowered make any diference to the cooling system ,am thinking of levelling her out just in case anyway.

No it won't affect it in normal use (IMHO), but note the instructions re bleeding and having the van at a suitable nose up posture during bleeding (like on a steep hill !!)

[Red Westie]

A bit more science: Cooling systems are designed to pressurize in order to raise the boiling point of the coolant, so instead of boiling at 100C the coolant doesn't boil until it's several degrees higher. This gives the coolant more capacity to absorb heat as well as sealing the system to ensure that coolant doesn't evaporate away. So you see it is very important that the pressure cap functions correctly in order for the cooling system to operate as it was designed.
Martin

[sarahautobus]

cheers we have ordered a new thermostate,a blue darlek,level sensor for header tank because its probably knacked after overheating. and the temp guage has stopped working all of a sudden, its still bugging me as to why the previous owner took out the rear under seat heater unit and the heater fan does not work .