Technical Overheating/cooling system problems

[teulk]

My girlfriend was driving home this evening and most of her journey involves sitting in traffic for at least 45mins. Up until today there have been no problems, i.e temp going up, fan kicks in temp goes down and so on...........Tonight however temp went right up into red and no hot air. When i checked the pressure was so great it was forcing the water out of the cap on the filler tank (hense loss of coolant, air in system) First of all what would cause this to happen as prior to this there have been no problems at all. Ive just been trying for two hours to remove the air (ive done this severals time before when i changed the coolant) and i just cant shift it. The front bleed screw has no signs of air comming out but the rear one has loads of air. Ive topped up, bled till no air coming from the rear bleed screw ran engine but the pressure keeps forcing water out of the fillertank - bled rear bleed screw, loads of air, topped up and tried again but i cant shift it ( ive bled and topped up at least a dozen times). Is it possible for air to be getting into the cooling system from somewhere or should i start from scratch and dump all the coolant............. Could my head gasket be gone ??

 

[custard]

head gasket failure can allow exhaust gasses into the coolant system and give pressure
sticking thermostat,failed cooling fan amongst other things can cause that.
how is the engine running?do you see any oil in the coolant?

 

[teulk]

The engine is running fine and no different to before. I cant say the fan kicked in as i didnt let the temp get that hot as the water was pouring out of the filler cap at arount the halfway mark on the temp guage. Tomorrow im going to drain the whole system and refill it from scratch - i'll check for signs of oil in the coolant when i dump it. So is there any sure tell tale signs that exhaust gases are getting into the cooling system thus indicatating failed head gasket ?

 

[KeithT]

The engine is running fine and no different to before. I cant say the fan kicked in as i didnt let the temp get that hot as the water was pouring out of the filler cap at arount the halfway mark on the temp guage. Tomorrow im going to drain the whole system and refill it from scratch - i'll check for signs of oil in the coolant when i dump it. So is there any sure tell tale signs that exhaust gases are getting into the cooling system thus indicatating failed head gasket ?

Check or change the thermostat it may be stopping the coolant circulating properly & preventing proper bleeding. Leave it too long & you will be replacing the head gasket!

 

[teulk]

It seems the problems start at the point the thermostat should open i think. This is what i noticed, i unscrewed the rear bleed screw and made sure only water was coming out, started engine and let temp and pressure build up. I unscrewed rear bleed screw ever so slightly to watch for air/water coming out. Now up to the point where the thermostat opens only water from the bleed point but around the point it opens thats when the air/steam starts coming out the bleed point. Also that is when the pressure really builds up and starts forcing coolant out of the filler cap.

 

[teulk]

Custard Boy and Keith T i cant thank you enough, you were spot on with the thermostat possibly being at fault - it was stuck closed, fitted a new one and all seems ok now - I just hope that i havent caused any problems with the head gasket with all the pressure build up when i was messing around with it yesterday. Anyway once again thanks for your help

 

[OLLEY]

wHEN THE CAR IS STARTED UP THE COOLANT SEEMS TO DISSAPPEAR HOW DO YOU BLEED THE SYSTEM ON A PUNTO

 

[Most Easterly Pandas]

wHEN THE CAR IS STARTED UP THE COOLANT SEEMS TO DISSAPPEAR HOW DO YOU BLEED THE SYSTEM ON A PUNTO

I think you'll find a bleed plug on the radiator (possibly top left corner (when looking at car from front)), and there might/should be one high up near the heater matrix in the piping somewhere.

Simply start the car up, top the expansion tank up, and open bleed screws until coolant comes out (expansion tank will need refilling when finished) and then re-tighten. Job done

Jon.

 

[fiestinjo]

how important is to switch to hot air in cabin when bleeding the system? I dont see that you have mention that, but doesnt the water get to the small radiator that way and pushes the air locks out?

 

[Most Easterly Pandas]

how important is to switch to hot air in cabin when bleeding the system? I dont see that you have mention that, but doesnt the water get to the small radiator that way and pushes the air locks out?

Very well spotted.

As mentioned by fiestinjo, turn heat dial to fully hot before doing what I've mentioned in post 8

Jon.

 

[fiestinjo]

would air locks be more "visible" on high or low speeds? Does the speed matters?

 

[MattMk1]

there might/should be one high up near the heater matrix in the piping somewhere.

there is another one at the back of the throttle body

 

[Most Easterly Pandas]

would air locks be more "visible" on high or low speeds? Does the speed matters?

What do you mean speed's? Engine RPM speed, or ventilation fan speed?

Car running at Idle should be fine

 

[fiestinjo]

i meant km/h...speed of the car.