G40 losing coolant after long run

[breadman]

Sorry to have spoken out of turn yet again Andy.

[Yoof]

Sorry to have spoken out of turn yet again Andy.

Don't chat shit then?

[breadman]

Who asked you for your input? Shut the fuck up Pete.

[GSBellew]

Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.

Yeah I had it out when I was changing the thermo switch and gave it what I thought was a very good cleaning out with the hose, might give it another go though  

I've the new thermostat housing just waiting for the new elbow which should be in tomorrow so I will see if it sorts it, after that I can only think of the water pump maybe not circulating the water around so the water in the radiator may be cooling which is why the fan is not running but the water in the block is not getting cooled?

[GSBellew]

Ok,

I changed the housing and refitted everything, then found a leak where the bottom radiator hose connected to the thermostat housing elbow, got a new pipe today and fitted it, no leak now. Filled and bled the system and ran it up to temperature in the garage, it got pretty hot (indicated 100+ before the fan kicked  

When it did it cooled down quickly, so I took it for a spin on to the motorway, the gauge sat at 110 the whole way (about 5 miles) I stopped before doing the return leg, still 110 indicated, but checked the engine bay no cooling fan running   top pipe to radiator was hot, bottom & the radiator itself cold, thermostat is new.

I did the return run and the temperature stayed pretty much constant at 100 to 110, thought it was ok if a bit hot and confused about the fan, but when I got home it had lost some of its coolant still no radiator fan, let it idle and the fan came on  

I am wondering if perhaps the waterpump is not circulating the coolant which is why the engine is hot and the radiator is cold? At idle gravity may be enough to make it circulate which could be why the fan comes on at idle but not on the road?

[Andy]

It's worth checking for sure! Presume the system has been thoroughly bled?

[GSBellew]

I bled it by opening the white plastic screw on the valve at the heater matrix / fan setup with the interior heating setting on 'hot' that should do it shouldnt it?

[Yoof]

I usually bleed it with the header tank cap off, wait until the thermostat has opened, then put the cap back on and bleed from the heater matrix.

[GSBellew]

I'll try that way tomorrow.

I changed the water pump today, the impeller was ok, but the O ring was fecked and it looks like it had been leaking at the bottom of the pump.

[GSBellew]

Still the same, but not as bad if that makes any sense?

Its staying cooler than before, sub 100 most of the time still losing a bit of coolant though  

I noticed the fan is not kicking in till over 100 and is only hitting the low speed, it is a new VW thermo switch should I assume its faulty or suspect the black sender of giving a higher reading then it really is? I'm more inclined to suspect the thermo switch myself  

I also did another compression test when warm like it says in the instructions (did it cold last time as I had no thermostat housing at the time so couldn't run it to warm it up.

I got 10.5 Bar / 150psi on all 4 cylinders so the head gasket definitely should be ok, could it just be the fan not kicking in until it is too late and allowing the temperature to get too high? Its also not running on when the car is switched off like it used to, the fan is working when shorted out.

I'm thinking out loud now, would it be worth doing some sort of flush on the radiator, in case its blocked or partially blocked 

[PeteG40]

sound like the rad could be blocked, especially under where the sensor goes.  Its shallow at that point and easily silted up

[GSBellew]

sound like the rad could be blocked, especially under where the sensor goes.  Its shallow at that point and easily silted up

What's the best way to check / fix that if thats what it is?

Take it out again and use the hose or one get of the coolant system flush additives? 

[PeteG40]

flush rad with it off and the sensor out i'd say

[liam]

when i had this problem my rad fan was to blame, it worked but not as it was supposed to, i noticed that straight away when i put another rad fan on, might be worth changing it mate i got a second hand one from volksmagic for £25.

[breadman]

Just a thought, I see you say that you've flushed the cooling system but did you take the rad out to give it a real good go? It may pay to reverse flush the radiator particularly if it's the original as they do silt up over time. I reckon it's also worth doing the heater matrix (pipes disconnected) then reflush the engine (thermostat out) to give it all a really good clean.
It'll only cost you a bit of time (apart from another bottle of antifreeze!) rather than keep replacing bits uneccessarily, might be worth a try?
Good luck.

Remember I suggested this before, I reckon its got to be worth a go.