172 overheating

[-J-]

Strange issue, stop light has come on a few times and then gone off after a second in past few days.

Today I have noticed that the temp gauge gets up to normal, then if you put your foot down goes right to the top, I'd you then back off it slowly drips back to half?

The car was low on coolent when I checked so topped it up, put the engine on and the bottle filled to the top?

Rad is cold and the fan is sill coming on, car drives fine, and no warning lights on the dash, top rad hose does not feel hot?

Unplugged the temp sensor and the gauge drops to cold as expected, no mayo on the oil cap.

Could it be a jammed thermostat or something worse?

 

[MicKPM]

sounds like either an air lock or a faulty coolant system not holding pressure.

Start by bleeding it when its properly stone cold bud

Mick

 

[-J-]

sounds like either an air lock or a faulty coolant system not holding pressure.

Start by bleeding it when its properly stone cold bud

Mick

Bleeding it, 10mm bolt on thermostat housing I presume?

Can airlocks just happen? I had coolent and hoses changed about 4 months back and all has been ok until today

 

[MicKPM]

if the system has run low yes, air can get in. Bleed by firstly opening the bleeder on the stat house yes till you get air free coolant flowing then close it. Then move to the heater matrix pipe which should also have a bleed point on it.

Mick

 

[-J-]

Cheers Mick I'll give it a try

 

[-J-]

Hmmm just been out and looked, coolent has dropped to Min mark again.

 

[-J-]

Right, no air in the system, coolent seems to be dropping but cant see where it's going.

Top rad hose is cool to the touch and the temp rises after about 2 min driving.

Likely hood of a shafted thermostat? Are they easy to change?

 

[MicKPM]

If the stat had gone the top hose would start to get warm straight away (eventually getting hot). You've most likely got a blockage, duff water pump or a system leak (eg, faulty cap, water pump or even head gasket).

 

[mr.pink87]

Check the hoses that go to the heater matrix for leaks and have a look around the bay if there are any wet spots.

 

[-J-]

No leaking spotted on the floor around the car, no signs of mayo in the oil either, will check the heater matrix ( where is it lol )

 

[-J-]

If the stat had gone the top hose would start to get warm straight away (eventually getting hot). You've most likely got a blockage, duff water pump or a system leak (eg, faulty cap, water pump or even head gasket).

How would I check the pump / bottle cap or what other signs are there of the head gasket?

The car seems fine to drive still, the fan comes on and runs for a few seconds when the car is switched off.

 

[MicKPM]

It could even be a faulty temp sender or wiring issue. I had an F4R Scenic do something similar and everyone was convinced it was HGF but in the end it was a poor earth in the main loom.

Trouble is these faults take time and a keen eye to fix which isnt something i could honestly advise you on over the net.

Mick

 

[-J-]

It could even be a faulty temp sender or wiring issue. I had an F4R Scenic do something similar and everyone was convinced it was HGF but in the end it was a poor earth in the main loom.

Trouble is these faults take time and a keen eye to fix which isnt something i could honestly advise you on over the net.

Mick

Cheers mate, will start by getting the system pressure checked and go from there I think,
Pity you are not closer!