Cooling - Any Ideas?

Hi,

Drove to a mates this morning to help him with his terrafirma lift, everything was fine.

Got in it this afternoon and as I got onto the main road, I noticed the temp gauge was still cold not moved at all.

Carried on driving till I got home, hAlf hour journey all in all. Popped bonnet, rad was cool, expansion tank was cold. Strange........

Started it up 10 mins later to move it then rad became hot and so did the coolant res. Temp gauge still not moved.

Any ideas? I thought it could be the thermostat but wanted to check before I pull it to bits.

Cheers!

Did you check the heater matrix pipe's to see if they was hot.
But it sound's like the stat to me.

A few pipes on the top were hot but not all of them.

Could the engine have been damaged in anyway? Or is it something or nothing?

Oh and the heaters were blowing hot while driving.

Sounds like it could be a dodgy thermostat, or possibly a sporadic airlock somewhere.

I would replace the stat, at the same time drain the coolant completely and re-fill it in the recommended way (through top of thermostat housing on 300 Tdi iirc) and give it a whirl.

Worse case scenario could be coolant pump not pumping? Have you noticed any leaks or unusual noises from the front of the engine?

Langers said:

Sounds like it could be a dodgy thermostat, or possibly a sporadic airlock somewhere.

I would replace the stat, at the same time drain the coolant completely and re-fill it in the recommended way (through top of thermostat housing on 300 Tdi iirc) and give it a whirl.

Worse case scenario could be coolant pump not pumping? Have you noticed any leaks or unusual noises from the front of the engine?

Click to expand...

Nope, no leaks anywhere. Any way the pump could be tested without removal?

It was ejecting coolant through the cap every now and then before this happened today.

What temperature should the thermostat open at? Will check it when I finish work in the morning.

matthew2riches said:

Nope, no leaks anywhere. Any way the pump could be tested without removal?

It was ejecting coolant through the cap every now and then before this happened today.

What temperature should the thermostat open at? Will check it when I finish work in the morning.

Click to expand...

Ejecting coolant isn't good unless the system had been overfilled. After a run with the engine at operating temperature, how do the rad hoses feel? They should be quite squashy with a good amount of give.

Thermostat for a 300 should open at 88*C or thereabouts - they are a common failure point, particularly if the coolant system hasn't been maintained properly and is filled with gungey crap. They are cheap, so if you have to replace it, go for an OE one as opposed to the even cheaper (Britpart) alternative.

Langers said:

Ejecting coolant isn't good unless the system had been overfilled. After a run with the engine at operating temperature, how do the rad hoses feel? They should be quite squashy with a good amount of give.

Thermostat for a 300 should open at 88*C or thereabouts - they are a common failure point, particularly if the coolant system hasn't been maintained properly and is filled with gungey crap. They are cheap, so if you have to replace it, go for an OE one as opposed to the even cheaper (Britpart) alternative.

Click to expand...

Yeah, they were nice and soft. They weren't hard. There doesn't seem to be any suction or blowing coming from the res if I put my hand over it.

I'll check the thermostat tomorrow and replace it anyway as they're only a few quid then see if the temperature needle comes back to life.

matthew2riches said:

Yeah, they were nice and soft. They weren't hard. There doesn't seem to be any suction or blowing coming from the res if I put my hand over it.

I'll check the thermostat tomorrow and replace it anyway as they're only a few quid then see if the temperature needle comes back to life.

Click to expand...

Worth checking the temp sender as well, check it's still got its wire attached properly, replace if new thermostat doesn't bring needle back up again.

Just took the thermostat out of the housing and dropped it in some boiling water. It opens and closes about 1/2 inch. Sound ok?

Where is the temp sender on these?

just below thermostat ensure system is full using the two plugs and fill till all over flow including expansion tank ,excess will blow out harmlessly,check rad is hot all over after,expansion tank level aint no guarrentee whats in engine,ive done so many overheated engines with low coolant in engine but still coolant in tank,low coolant will inhibit thermostat opening and low reading on sender

Also just popped out the temp sender, there is resistance between the two pins.

I am just going to assemble it all back together, fill it up through the two plugs and connect everything back and to see what happens.

Will post my results.

I've stuck a new thermostat in the housing, cleaned up the multi-plug on the temp sender and the bottom of the thermostat housing.... We have a gauge again. Need to take it for a bomb tomorrow and get it hot to see if my efforts were in vein. Still - It is one step further than I was at

matthew2riches said:

I've stuck a new thermostat in the housing, cleaned up the multi-plug on the temp sender and the bottom of the thermostat housing.... We have a gauge again. Need to take it for a bomb tomorrow and get it hot to see if my efforts were in vein. Still - It is one step further than I was at

Click to expand...

Good, my bet is it was the 'stat that was causing the problem, so I reckon it'll be fine now.

Seems like exactly the same problem on my Disco 2 TD5 '99 - gauge isn't moving at all. I only checked the temp sender near top hose and head connection. It has resistance between pins and - if I disconnect it - red light in dashboards lit's up. Now the questions - where else I should look for potential problem?