Renault Migraine temp

**pangr** · 24th March 2005

Temperature guage on my motor goes up and down as I drive along. Goes all the way to HOT HOT and then drastically falls to warm/medium.

The expansion tank is building up with intense pressure - so much so that water is forced out from the lid, therefore losing water in the radiator.

The last thing I did was put some RadWeld in the exspansion tank because the radiator was leaking. I think the leak has stopped now.

Has anybody experienced this problem and can advise a solution?

Appreciated...

**Little John** · 24th March 2005

Im no expert but this happened to me after I had the front end of my 206 rebuilt. went to london and got stuck in traffic and the temps went up.

It turned out to be the fan was fucked, the dodgy garage didnt replace it after the accident and it was only when I was stoped in traffic and no air was going through the radiator the fan should have kicked in to cool it down and it didnt.

In the middle of summer I had the heaters on and windows open to keep it cool.

See if your fan kicks in, just leave it running for 5 minutes maybe more so that it can get warm and see if the fan comes on when the temps rise if it doesnt then get it checked out, it could be a dirty contact or somthing. thats what th garage said it was to me even though it took a day for them to clean the contact and the whole fan caseing and blades and everything hmmmm.

**pangr** · 24th March 2005

Cheers for the reply, I did try the fan and unfortunately it worked. The temp only goes up high when I drive fast on the motorway. I can keep it from extreme high when I keep the car under 60mph. But the temp still goes up and down from warm to hot.
When I leave the car idle and the fan eventually comes on, the temperature does rise to medium/hot but not as high as when I am motoring at 70/80mph.

**Pegasus** · 25th March 2005

I've seen blown head gasket's cause this.

Get a pressure tester on it.

**johnenty** · 25th March 2005

Could it be the rad weld in the pipes? I have only ever seen that stuff poured direct in to the radiator not the expnsion tank maybe it has settled in the pipes and is reducing the flow of water to or from the radiator to the engine

**marcode** · 25th March 2005

Originally Posted by Pegasus Team

I've seen blown head gasket's cause this.

Get a pressure tester on it.

ye, a blown head gasket cost me 500 quid a couple of months ago after the car had leaked oil and then one day the temps rocketed when sitting in traffic.

when i got to work (had to drive it hot for about another 5 miles) called the AA and the guy basically just said "yep, its fucked."

**pangr** · 26th March 2005

I have found an oil leak just underneath the Exhaust pipe manifold (Manifold connecting to the engine) and the car has a constant misfire. It tends to misfire on idle - usually hear it pop very lightly when listening to the exhaust at the rear of the car. The idle is also felt inside the car. The car usually is very quiet and sometimes you may not even think the engine is running, but lately, the car vibrates when stationary in idle. Does this sound very likely that the head gasket is gone??? IF So...

FS: R-reg Renault Megane 1.6 sports coupe e, low milage for year, immaculate condition inside and out. Owned from new, AC, e/windows e/sunroof, metalic black, 17" low profiles, New clutch, gearbox, drive shafts/CV joints, bearings. Part service records. Runs EXTREMELY well, sale due to new company car.
Starts first time all of the time hot or cold. :thumbs

**pangr** · 26th March 2005

Originally Posted by johnenty

Could it be the rad weld in the pipes? I have only ever seen that stuff poured direct in to the radiator not the expnsion tank maybe it has settled in the pipes and is reducing the flow of water to or from the radiator to the engine

I read the bottle and it did mention about putting it into the expansion tank if you have a sealed radiator unit which I think I do have. But, my next job will be to empty the system and clean the pipes in case your theory is correct. This may also get rid of any air pockets in the system.

Thanks for the tip...

**pangr** · 26th March 2005

Originally Posted by Pegasus Team

I've seen blown head gasket's cause this.

Get a pressure tester on it.

Is pressure testing something I can do myself or should it be left to the professionals?

If so, can you advise what to do?

Rgds

**Pegasus** · 26th March 2005

You can do it yourself if you have the actual pressure tester.

If not, any garage that has the kit can do it in under 2 minutes and tell you if the cooling system is loosing pressure or not.

**pangr** · 28th March 2005

Pipes are all clear. Drained the system and refilled. Still has the same problem...

My neighbour mentioned it could be the thermostat. It apparently opens to allow warter to flow around the radiator when the engine warms up. If my car is not opening the valve then the pressure builds up and exits from the weakest point - the expansion tank. Hence the temp goes up high and then drops down when the presure is released. :nowords:

Maybe I will try testing the thermostat first. Apparently they are quite cheap. If that dont work then I will take it to a garage for presure testing.

**Pegasus** · 28th March 2005

If the stat was fully stuck then you would definately know about it, although it is quite possible that it is partially sticking and not being able to open up fully (hence the overheating at high speed due to restricted water flow).

Being the "doom & gloom" merchant that I am though (and the fact that I have had the same problem more than once on different cars), I still can't help thinking it's a failed head gasket.

Let us know either way.

**urbsy** · 28th March 2005

Take the thermostat out and drop it in some boiling water, if it opens fully then its fine.

I'd agree with PT, it's looking like the head gasket could be at fault though.

urbsy

**nobber30** · 29th March 2005

this may be totaly unrelated but i had simalar problem with my sisters rover 414 after replaceing head gasket so of i trotted to rover and asked the dude there turns out i hadnt put enough antifreeze in after draining the system wonder if the leek that you stopped has lost to much anti freeze before hand

**weejabba** · 29th March 2005

Headgasket written allover it im afraid mate!

**Big Red** · 29th March 2005

Sounds like it is almost certian, the head gasket is gone.
easiest and quickest test is nip to your local mot station, and get them to "snif" the gases in the coolant bottle with the exhaust gas analyser.

Seriously.
Any combustion gases in the coolant system will show up a reading in hydrocarbons on the gas analyser.
There should be no combustion gases in the cooling system unless they are getting through a failed head gasket.
Takes no time at all and is a very reliable test.
If no hydrocarbons present, then look at cooling/circulation problem.

Gordon

**cosmicma** · 29th March 2005

it sounds as if your doing what i tend to do
convince myself it's not the head gasket it's something else ( cos there a pain to change compared to just a coolant blockage ) but unfortunatly it's sounds like the head gasket to me
it sounds as if the exhaust is pressurising the water system so at low revs it won't be too bad but the higher the revs the more pressure which stops the water flowing
you'l probably find your radiater is not getting as warm as it should be ( maybe even stone cold in places ) because theres very little water flow though it

my advice is get the head gasket changed now before it gets any worse and causes some real damage
after you have eliminated every possible other reason of course

**pangr** · 30th March 2005

Ok. Thats it... Im definitely goin to sell it or part ex for another motor.

When I start it up, it sound very sh*te with misfires etc. heavy white fumes comes out of the exhaust (not black or blue fumes) and it doesnt smell of petrol, more damp than anything. Its more than Ive ever seen. But after a few revs, it seems OK and the misfire disappears. Once the engine is hot, misfire is back and very reglular.

Thank for all your help. I wished I didnt ask now. But I have to face facts, the car has got to go. CHEERS GUYS...

**Big Red** · 31st March 2005

The misfire you are getting when you first start it up is water getting into a cylinder when parked, it gets onto a plug and stops it from firing.
Once this clears, it will be ok until the system gets pressurised, then water will be getting back in and make it run like sh*t.
The white smoke at start up is the water getting burnt of, just like a kettle boiling, more steam really.
All the above symptoms are definately a blown head gasket, sorry:grr:

Gordon