Overheating after fitting new Thermostat?

Just had a faulty thermostat diagnosed.. the head was checked and all fine

Just fitted the new one (checked it worked before fitting)

Put water in (only water to check its working) left cap off for ages kept topping up.. now after a short short drive it overheated and the top radiator hose expanded so its pressurizing, could this mean i put too much water in? shall i carry on letting idle with cap off longer?

is it cos i am using just water? do i need antifreeze in it too just to test it?

no you dont need anti freeze to test it.. water is fine for a short time.
If the top hose is rock hard then you have a problem.

Obviously if the engine is working normall the top hose will become harder as the cooling system pressurises but you should be able to flex it.

which rangie/engine do you have

4.0 v8 1999

head has been tested, brand new thermostat.. do u think it just needs bleeding more?

right let me check i'm bleeding it correctly:

1. i filled up header tank with water
2. started car
3. put heaters on max
4. when water level drops keep topping up
5. i've left the cap off
6. engines getting hot, top hose still flexing but hot
7. now excess water is coming back out of top of header tank

then do i keep it running... for longer?

and then do i wait for the water to stop bubbling out the top of the tank? just wait till its perfectly still?

put the cap on tight it is a pressure cap and if it is working properlly will allow the cooling system to pressurise and lower the boiling point of the cooling fluid, which means it works more efficentlly.

what state is the viscous fan in?

serpentine belt

radiator.

lowfat said:

put the cap on tight it is a pressure cap and if it is working properlly will allow the cooling system to pressurise and lower the boiling point of the cooling fluid, which means it works more efficentlly.

what state is the viscous fan in?

serpentine belt

radiator.

Click to expand...

Raise the boiling point ..

So even if theres still bubbles coming through the pipe on the bottom of the tank its ok to put cap on?

fan and belts look fine

And if i put that cap back on now, and it starts to overheat, could it be the cap at fault?

ok, after running it for about 45 minutes, kept topping up, bubbles coming out tank.. before i could put the cap on, the top hose pressurized and start spitting boiling water out the tank everywhere and the temp gauge shot up, so i turned it off... shall i try it again when its cooled down a bit

get the front end up as high as you can (a set of ramps is ideal) it sounds like it is airlocked. are you sure you put the stat in the right way? ( i know. grandma sucking eggs but it's been done before)

take the small pipe off and make sure its clear. water must come back, from rad, as its only small hose it some times blocks..

Where is everybody today? lol.. need help

Well.. it cooled down a bit, topped it up, stuck cap on.. temp stayed in middle.. top hose did get firm, left to idle for 20 minutes.. then turned off.. after off loads of air was coming into the header tank from the bottom pipe, so is this a sign of the system clearing the air? shall i repeat this process? leave to cool, top up if ness idle for 20 minutes or until hot hot, then off to clear the air?

garydavidson123 said:

Where is everybody today? lol.. need help

Well.. it cooled down a bit, topped it up, stuck cap on.. temp stayed in middle.. top hose did get firm, left to idle for 20 minutes.. then turned off.. after off loads of air was coming into the header tank from the bottom pipe, so is this a sign of the system clearing the air? shall i repeat this process? leave to cool, top up if ness idle for 20 minutes or until hot hot, then off to clear the air?

Click to expand...

Av ya checked wot j the range suggested?

the little pipe on top of the rad? running past the battery back to the top of the tank? no, but it seems clear and air/water is coming out the tiny hole in the neck of the tank

as for having it high, its sitting quite low at the front cos i've got an eas fault too

but when i turned it off lots of air bubbles where coming from the bottom pipe of the header tank, and top hose has become flexible again when cooler...

how long does it take to bleed the air out usually?

oh and when you have got running properly don't forget you have to drain the water out and do it all again but with anti freeze mix.......

:hurt::boink:

you need the front of the motor high as possible to get the air out of the heater matrix...

yeah lol dont i know it! but i'll be happy knowing there's no other problems in the engine..

so cos its low, that could be causing these problems then? i must admit, one time i tried it, the heaters wouldnt blow out hot air, they are now though...

Try tunning it without the thermostat and see if it still overheats.

Test the thermostat in hot water and see if it actully works.

When the engine is running,c an you see movement of water? Are there bubbles in it?

New thermostat tested and working...

Yes, water is pumped from and to the tank...

Just after a while it seemed to get pressure in it... maybe airlock?

Topped up again, then cap on, idled good for 20 minutes without overheating, although top hose firm.. then when off air bubbles being sent back to tank from the hose at the bottom of the tank (from thermostat i think it is)