overheating --air-con ?????????

hi everyone .. please help ,,heres the story ,,, i have a 2000 v8 4.6 vogue with thor engine and is petrol/lpg ( filled up at 64p per litre yesterday thats the good news ) anyway was off to caravan for long weekend and drove 6 mile with outside temreature at 78 degrees stopped to pick wifey up and sat with car ticking over for 5 mins and put air/con on and then drove approx 3 miles due to chatting to wifey didnt notice temperature clock went from 12 oclock normal right up to red with red light flashing.. pullrd over and vented tank and boy was it steaming refilled header tank when cooled down and carried on . after 1/2 mile up it went again so stopped again let it all cool down and refilled header tank again ????? started off again and temp started to go up again ????? so turned a/c off and it all squared up nicely to 12 oclock again .... so carried on drove steady and 120 later arriving at caravan had no probs all the way ... so whats going on ????????? when a/c was on it was ice cool as expected but does it need re gassing ? as ive not used a/c for 12 months . or is the a/c knackered .. there is also showing on the he/vac display the open book ??? but that has been on there long time ...have had the car 3 years and never had this problem ? so any help or suggestions would be greatly appreciated ,,,cheers MOZZ the RE-SYNC man ....kind regards mozz

How's your fans? Could be something wrong with one or both

The A/C system uses a radiator called a condensor to re-cool the gas down after it has been heated up by removing heat from the air going into the car....

As can be imagined, this condensor get very warm as it is transferring quite a bit of heat energy out of the gas to cool it back down again so you get nice cold air from the A/C....

Unfortunaly this condensor sits infront of the Main Engine Cooling Radiator, and has the effect of raising the Engine Coolant temperature.....

I get this on my Diesel, without A/C the Temp barely touches the white area...with A/C on it sits squarely at 12o'clock.

It could be a sign to think about overhauling the coolant system and flush the radiator through, check your viscous fan unit for correct operation too, as mine does cut in and out with the A/C on.....

There are a pair of electric fans that are supposed to switch on when the A/C temp gets warm, to aid cooling ofthe Condensor and Rad.....check these work too....

hi ,sainty and druim .had a mega service approx two months ago and all coolant was dropped flushed and refilled with coolant added .. not sure how to check fans or sensor ?????????? cheers lads mozz . p.s. all fans have also been checkked or broken blades etc

i would be checking my radiator for cold spots if i were you!!

mozz smith said:

hi ,sainty and druim .had a mega service approx two months ago and all coolant was dropped flushed and refilled with coolant added .. not sure how to check fans or sensor ?????????? cheers lads mozz . p.s. all fans have also been checkked or broken blades etc

Click to expand...

Viscous fan can be checked with rolled up news paper, you shouldn't be able to stop it, watch you fingers!

Air-con fan easy check, idle car set hevac to LO i.e. cold full request and wait they should start as they gets hot and not cooled by wind or viscous fan, if viscous fan runs the air-con fans probably won't kick in so do it with cold engine, maybe they can be forced with diagnostics?

Don't assume everything is well just because it has been serviced, new liquids etc.

Mozz, I would bet on it being the viscous fan, I can give you a mod to bring on the aircon fans based on engine temperature as supplementary cooling, the V8 engine ECU should also activate the fans when the engine temp goes too high but on the V8 you still need the viscous.

Erratic temp gauge going from 12 to red?
Expansion tank pressure excessive?
Just does it some of the time?

Been there. Got the badge.

Could be wrong....

Block crack

mmmmmmmmmmmmm. thanks for all your comments ,,looks like a new sensor as datatek suggests ,will be visiting my mucker joe emmott this week and he will sort it !!!! checked all water levels etc this morning and all ok .wont use a/c till i get it back from emmotts ,,will keep you all posted with updates , once again many thanks for your contributions ,,,mozz

hi lads have just come back from my caravan (sun night ) have now travelled approx 300 mile since it started the problems ... car has been great but of course i havent turned the a/c on so will do it tomorrow and see what happens before i go up to emmotts of colne ,,,cheers will update again ,, kind regards mozz

hi lads , latest update === as per my original story ,it has happened again today . exactly same as last week , have checked the 2 a/c fans both working perfect .... viscous fan checked and working so now at a complete blank as to what next need help desperately , any imput wanted asap ,, travelled back home today at average 70 mph with a/c switched off and all perfect ?????????? so why does it overheat after a/c switch on all ice cool for 10mins then shuts itself off by overheating ,,,,very very strange ,, ok lads look forward to all your replies ,kind regards mozz p.s. free present to whoever comes up with definitive answer ...

checked that rad for cold spots yet?

I'd be looking at your engine rad very carefully. If it's just working well enough to hold the engine temperature down but can't handle the extra heat from the air con condensor then I'd be thinking that you've got a load of sludge or a blockage in there.

At least, pipes off and hosepipe up the output, preferably rad out.

mozz smith said:

hi lads , latest update === as per my original story ,it has happened again today . exactly same as last week , have checked the 2 a/c fans both working perfect .... viscous fan checked and working so now at a complete blank as to what next need help desperately , any imput wanted asap ,, travelled back home today at average 70 mph with a/c switched off and all perfect ?????????? so why does it overheat after a/c switch on all ice cool for 10mins then shuts itself off by overheating ,,,,very very strange ,, ok lads look forward to all your replies ,kind regards mozz p.s. free present to whoever comes up with definitive answer ...

Click to expand...

The cooling system is marginal on the V8 at the best of times, if part of the cooling system is less than perfect, the heat from the aircon condensor is enough to cause an overheat. If you are sure the viscous fan is OK, then it's a case of going through the rest of the system, water pump, thermostat, and RAD. A silted up RAD is a common problem as is a stuck thermostat. Also worth checking the LPG plumbing and the pressure cap on the expansion tank

hi keith thanks for the info ,i tried ringing you but must have been out or busy will try in the morning if thats ok .cheers mozz

Hi Mozz, sorry I missed you, out working till late in the good weather. Out this morning to the tip etc and again after lunch. In for an hour from about 12 your time.