More overheating woes.

[Rtaylor2208]

The cabby is playing up again and is overheating, at least I can be sure of it now the brown sensor was replaced and the gauge is more accurate.

Basically under 40 mph it's ok ish staying between half and 3 quarters.

Above 40 it starts to climb.

The heaters blow nice and hot and there is no symptoms of a failed head gasket, I.e mayo, loss of coolant etc etc.

I did notice that the top hose that leads off from the thermostat housing across to the rocker cover side seems a bit limp as if there is no pressure.

I'm thinking possibly a non opening thermostat. Does that sound possible going on the symptoms?

[scjimbo]

Gotta be worth a try at £10

[Rtaylor2208]

To be honest I'm trying to avoid buying yet more parts on the chance it'll fix it, not to mention another 5 litres of coolant considering it was only all replaced under 500 miles ago when I did the timing belt.

Testing the termostat with boiling water is most likely my next task but just looking for a second opinion before takin things apart.

[scjimbo]

If it was me, and judging by the symptoms you are describing that would definitely be my first try. Mind you daft question, and I probably already know the answer was the car hot when you squeezed the top hose? Also don't use actually boiling water on the thermostat test or you will knacker it.

[e30mtech]

sounds like could be water pump to me.

[Rtaylor2208]

Water pump is another candidate, I never changed it when I did the belt and tensioner as it looked fairly recent should have known better to be honest but at the time money was tight.

The engine was hot when checking the hoses. One thing I did notice was that when opening the bleed valve water would only come out after the gauge was half way, and at times only when I reved the engine. In the past when bleeding the system it has always trickled out pretty much at any temp. This was also another reason I was thinking it may be thermostat.

[Andyboy]

It could even be a knackered rad. Many look okay but are silted up at the bottom and I' ve had one with the same symptoms. I would only use a genuine BMW stat as well, not some ten quid special.

[Rtaylor2208]

Thanks Guys the rad was replaced under 1000 miles ago so I'm fairly confident that it should be ok.

Top hoses are a bit warmer than the bottom hose can't really quantify how much but they all get warm.

Looks like I'll try changing the thermostat first before going near the water pump.

[Rtaylor2208]

all are definetly too hot to hold for more than 3 seconds.