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[Sir Tigger KC]

Hi All,

My 2.5 V6 has started to overheat.  It's fine when cruising but as soon as I hit traffic it starts to overheat.  If I pull over and rev to about 2500rpm then the temp quickly drops again. 

The fans seem to be running OK and its recently had a new rad, new fan switches and the system flushed.  There are no signs of oil in the water or vice versa. 

Also there's no heat coming from the blowers... Any ideas??

Many thanks in advance 

[Lizzie_Zoom]

Hi All,

My 2.5 V6 has started to overheat.  It's fine when cruising but as soon as I hit traffic it starts to overheat.  If I pull over and rev to about 2500rpm then the temp quickly drops again. 

The fans seem to be running OK and its recently had a new rad, new fan switches and the system flushed.  There are no signs of oil in the water or vice versa. 

Also there's no heat coming from the blowers... Any ideas??

Many thanks in advance 

To what temparature?

Could be your thermostate 

[ScaniaV8]

Maybe an 'air lock' in system or failure in the Water pump/impeller too. May be worth checking out.

[Dave Elite]

Maybe an 'air lock' in system or failure in the Water pump/impeller too. May be worth checking out.

That was my first thought as well, one or more of the impeller blades could have snapped off, as it cooles when you rev it to 2500.

[Sir Tigger KC]

Thanks for your replies 

I forgot to mention that it dosn't overheat all the time.  Today I did over 100 miles, a mixture of dual carriageway cruising and stuck in traffic and it was fine.... :-/

So if some of the impellers have snapped off the waterpump, does that mean its not working well at slow revs, but does the job at higher revs?  :-?

[Kneepad]

I wonder if the thermostat is sticking intermittently in the closed position. Might be worth replacing it for all they cost.   :-/

[Sir Tigger KC]

I don't really understand how the thermostat works  , does that mean that if it's sticking in the closed position then its blocking the flow? and would that account for a lack of heat from the blowers?

If that's what is happening, why does the temp drop when I bring the revs up?

[henryd]

if the thermostat was sticking shut engine and heater would get hot but radiator will stay cold,the fact that your heater is cold may point to an airlock in the system,I presume that the heater was ok before this started happening

[cem_devecioglu]

have seen many cases that thermostat failed half open.. and dont give a real clue whats happening..

[cem_devecioglu]

check the coolant hose on the right and see if it gets hot immediately or slowly when the engine is cold..

[Sir Tigger KC]

Thanks, I'll check that later as I've just got in and its all hot.  (not too hot tho! )

I've got more info though... I've done about 70 miles today again a mixture of cruising and slow traffic and all was OK, however it started raining just before I got home, so I put the blowers onto the windscreen.  The temp started to rise as soon as I hit traffic. 

Parked up at home and tested it with the blowers on and off. With the blowers off it sits just above 95 on tickover, with the blowers on it rises above 100 and at 105 I bring the revs up to drop the temp!

I'll check how the hoses get hot later when she's cold and give them all a good squeeze to see if I can shift an airlock.

Many thanks for the replies 

[DK MV6]

Hi.

Just want to check and see if you got any further info on this.
i just returned for a drive and the temp seemed to get a little high ( higher than normal ) and when i pulled over and rev´ed it a little the temp went back to normal. I leaned towards thinking about the waterpump as my radiator and both coolant hoses are hot. Only weird thing is that the top coolant hose seemed to be abnormal pressurize when i tried to sqeeze it. :-/

[Sir Tigger KC]

Hi DK,

No further info at the mo sorry. 

I've given the hoses a damn good squeeze so if there was an airlock, hopefully I've shifted it! Also the top right hose gets nicely warm from cold.

I'm going to do the thermostat first and if that dosn't cure it then the waterpump, if that dosn't fix it then I'm stumped!!

[Kneepad]

Hi DK,

No further info at the mo sorry. 

I've given the hoses a damn good squeeze so if there was an airlock, hopefully I've shifted it! Also the top right hose gets nicely warm from cold.

I'm going to do the thermostat first and if that dosn't cure it then the waterpump, if that dosn't fix it then I'm stumped!!

At least then, you can exclude that from the equation. Just be careful to get all the air out of the system.   

[plym ian]

this sounds like my problem to its so anoying