Overheating

[MrBlueSky]

Wonder if any of you have thoughts or experience of overheating problem.
Had the Vee out on a fast run then got stuck in traffic at a roundabout. Fans came on but gauge went higher & higher. Stopped for while to let everything cool and left engine cover off. Came back to normal temp after 20 mins parked up and rest of run OK. Water level seemed ok. Any thoughts why did not cool even when fans on. Got the Scottish run this w/end so don't want to be shown up in cloud of steam next to other Vee's.

 

[Jamesv6]

Did both the front and side fans come on?

 

[MrBlueSky]

Both sets were on when I stopped but not sure when front went on as I could not hear above traffic until I stopped.

 

[MarkK]

It's probably worth looking at the basics first. Check there's no debris in the radiator cooling fins, then flush the system out with a decent product like Forte Coolant Flush, with the thermostat removed.

The cooling system can bung up if the coolant isn't changed every 2 to 4 years, and you can end up with sludge at the bottom of the radiators and around small openings like the thermostat. It also turns acidic, which starts to oxidize the aluminium, which all helps to bung the system up further.

 

[MrBlueSky]

Thanks for the advice. Kind of went through this thought process myself but system was flushed and recharged with fresh fluid last month when I had a hose replaced. Good local garage had it today and did extensive testing. Pressure test on cooling system for 30 mins and no leak. Sniffer test for hydrocarbons in water -all fine. Temp gun on system and thermostat and fans all working at correct temp.
The mechanic said was a bit baffled and wondered if it was similar to a case he had with a Lamborghini a few years back. Long fast run had the radiator super cool but when car stopped the thermostat was temporarily swamped with cold water and closed.
Open to suggestions - Still baffled.

 

[MarkK]

Take the thermostat out! It's not really needed in the summer if you're doing long runs anyway, and eliminates another potential cause.

 

[MrBlueSky]

Good idea. Might just do that.

 

[Ali]

Take the thermostat out! It's not really needed in the summer if you're doing long runs anyway, and eliminates another potential cause.

With me and Simon chasing him this weekend he'll need it! :rofl:

 

[jimm]

if the fans are cutting on and off and temp seems normal could it not be some thing to do with the guage?. or check altenator as some one once said to me at a local garage if the car is over charging it could have this effect on things like temp needles? worth trying,,,, if you HOLD the window switch up with the window all the way up does this make the needle climb so the electrical system is under load ? lights on and heater on number4 also loads it making it climb. if it does then it is electrical not a engine water issue . let me know

 

[Brett]

Could just be a simple case of some nasty heat soak from the god awful cast exhaust manifolds and cats. Mine did a few times but never during normal driving and only for a few minutes at a time. It's something I am aware of on the car now it has a pair of water cooled turbo's so it's now fitted with an electric pump which is far more efficient.

 

[shinji]

if the fans are cutting on and off and temp seems normal could it not be some thing to do with the guage?. or check altenator as some one once said to me at a local garage if the car is over charging it could have this effect on things like temp needles? worth trying,,,, if you HOLD the window switch up with the window all the way up does this make the needle climb so the electrical system is under load ? lights on and heater on number4 also loads it making it climb. if it does then it is electrical not a engine water issue . let me know

You perfectly describe what happens after every time I close the windows and watching the temp needle rise.

I didn't know that it is a sign of overcharging from the alternator, I was putting it down to just funny French electrics. Are there any issues with alternator overcharging in the long term?

 

[Ollie1]

I have the same problem when putting the widows up on my ph1. I thought it was a dodgy earth but maybe I was wrong.

 

[jimm]

Hello mate check the voltage before you start and if you can link a mutimeter up with a couple of long wires inside the car from the battery as you are driving you should be able to see what the voltage is like going to the battery. 14v after starting dropping after a short while isnt uncommon. see what happens ? as you said funny french electrics lol . could also try an ammeter to check current ? Im not saying it is overcharging but worth eliminating as it costs nothing to check .

 

[MrBlueSky]

if the fans are cutting on and off and temp seems normal could it not be some thing to do with the guage?. or check altenator as some one once said to me at a local garage if the car is over charging it could have this effect on things like temp needles? worth trying,,,, if you HOLD the window switch up with the window all the way up does this make the needle climb so the electrical system is under load ? lights on and heater on number4 also loads it making it climb. if it does then it is electrical not a engine water issue . let me know

Thanks for the suggestion. Tried as you suggested and had all electrics full on and window buttons pulled up and the needle stayed fixed. No movement.
Will keep my eyes open for this in future.

 

[Zim1]

My V6 has done this on ocassion ... as long as the needle isn't going past the red and there isn't a Warning light Illuminated ... it's not a big problem !
There are lots of fans on the V6 and i dare say some don't work now as the cars are getting older ...
You will hear the main front fans kick in and the revs will drop significantly ... as long as this happens , you are OK ...
The top temp on the guage ( as long as the needle is still inside the guage and not bent right past it ) is about 108 degrees and this is OK for short periods of time ...
Remember that the engine is in the back with no auxillary cooling and enclosed in a tight space , so if you have driven the car hard , especially on a warm day , and then got stuck in traffic , it is normal for the guage to rise to near the red ... as long as it is not bent off off the dial ... you are OK ... just get some air through the rad by drivng forwards ! Ideally , to cool the engine fast ... you want high revs with no load ... ie. keep it in a low gear with the revs high and air flowing through the radiator but the throttle position barely open ... this will increase the coolant flow and lower the engine temp naturally as it is not working hard
Please do NOT Remove the thermostat ! This is poor advice i'm afraid to say
The thermostat is there only to bring the engine up to temperature quickly and will only open near boiling point to prevent engine damage ... by their design , they do not lock closed , if they fail , they stay open ( and many V6's already have this minor problem )
But removing it in a car with huge amounts of pipework from the engine in the rear to the radiator in the front and a silky smooth V6 Engine that ticks over so low ( and the water pump hardly operating )... means that the coolant will just continuously run back to the radiator and something as simple as a minor blockage in the engine will report back as normal because the coolant is being constantly cooled by the rad ... Part of the cylinder heads could bend / warp causing major engine damage and you wouldn't have a clue until the head gasket(s) fail !
On that note , the standard V6 fitted to the Laguna is notorious for head gasket problems at / over 100k ... very few of us have got near this mileage and our original gaskets are uprated and we have different cylinder heads ... but this is definately something to worry about for long term ownership ... Especially if the correct type coolant has been constantly topped up with water over the years causing cast aluminium corrossion and / or the car has been run for many miles without the thermostat !!
I have replaced my coolant with the correct Renault Type ages ago ( Hugely Expensive ) but my cambelt is due now and I will probably have new cylinder head gaskets fitted whilst the engine is out and they are doing the belts / water pump ... very little extra cost considering the inclusive labour and the Expensive belt kit ! Also , we have an awesome engine place close to us and for just £120 , they will clean / replace all the cylinder head valves etc. and polish ( very minor skim ) the heads prior to re-fitment ...
Something that we should all consider !!
As long as your engine runs normally under normal conditions ... there is no problem
As soon as there is a permenant and Constant rise in Engine Temperature ie. always close to the Red ... there is a problem !

 

[MrBlueSky]

Thanks for the input everyone. Had the Vee out on the Scottish Run on Sunday and covered about 400 faultless miles. After some comments made here and on the day I have come to the following conclusion regarding my sequence of events. The first issue I had was on a cold November night when the heater was blowing cold and then the gauge climbs higher and higher and then drops to zero. Clear signs I had no fluid. A faulty hose that leaked only under acceleration was the culprit and replaced, however it made me over sensitive to overheating......My recent issue on a very hot day (for Scotland) was after a long fast blast and then sitting idle. As I saw the gauge climb, as it would do before all the fans kick in, I panicked fearing water loss and crucially switched off the engine between moments of crawling forward towards the exit on the roundabout. This was probably the wrong thing to do as the water pump would not then get the chance to circulate the cooler water from the radiator, hence the engine stayed hot. As the gauge is not calibrated and does not really have a red zone it is hard to say how hot it really was. I should have left the engine running and let the cooling system do it's job.
Should know this as it was standard practice back in the days of running 5 GT turbos - Never turn off a hot engine, let it idle for a bit to cool. Hopefully re-learnt and everything ok from now on.