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[Sir Tigger KC]

My old girl has started to take a while to get up to temp and the LPG also is taking ages to kick in. 

I was thinking that the Stat was sticking but then today when the LPG didn't kick in I ragged it and then it did, but as soon as I get into slow traffic or car park etc then it goes back to petrol.

So wondering about the water pump.  There's no obvious leaks or anything else wrong. 

TIA. 

[Migv6 le Frog Fan]

Sounds like thermostat to me. Whats the temperature gauge doing ?

[Sir Tigger KC]

Sits at about 85 goes up to 90 when driven hard, back to 85 when in traffic.  The stat was my first thought TBH. 

[Kevin Wood]

If you start it up from cold, does the top rad. hose start warming up as soon as there's heat in the engine or does it stay cool until it's reached running temperature then suddenly get very hot?

Can you feel heat in the hoses to the evaporator while it's warming up?

[Sir Tigger KC]

Havn't done that yet.       Far too windy today!!   

[Sir Tigger KC]

After 10 minutes of idling it only gets to just before 80 degrees and the top hose is still cold, although there's some warmth in the hoses going to the vapouriser. 

So I guess the thermostat is stuck and it's only 2 years old as well!  What a @$%&er!   

[Kevin Wood]

Nope. Thermostat sounds fine if the top radiator hose is still cold.

[Sir Tigger KC]

O ...   

Any ideas then?   

[Kevin Wood]

I wonder if something is restricting the flow through the vapouriser? Blocked heater matrix? HBV issue? Depends how it's all plumbed, of course. Could be the water pump, I suppose. Plastic impeller that's started to break up, perhaps?

[Sir Tigger KC]

The vapouriser is plumbed direct from the back of the block through the vapouriser and back to the HBV.   

Pretty sure the water pump has metal impellers.  Fitted about 3 years/28000 miles ago at last cambelt change.

[Kevin Wood]

OK, so for decent flow through the vapouriser, the HBV and heater matrix do need to be free flowing.

Also, as the coolant temperature is sampled at the bridge where this flow exits, a blockage somewhere would slow down the coolant temperature reading.

I think you'd have signs of overheating too if the water pump had died.

[Sir Tigger KC]

I've just been out testing and it all seems to work better with the heating off, which would confirm what you've said.  I think I have a spare HBV somewhere, so maybe I'll try that. 

How about chucking some descaler or central heating cleaner in the header tank?   

[106pete]

Having very similar issue with mine and guessed thermostat but I'll have to check that pipe first I guess, the thermostat sounds a pita job on the v6.

I just did a 600mile trip to Essex and only hit 90deg while giving it some, although around town it's fine.

[Toledodude1973]

90deg is about right ...isn't it?

[Sir Tigger KC]

90deg is about right ...isn't it?