Overheating modern

[Peetee]

My partners Ford Galaxy has suffered cooling system issues for some time now (over 1000 miles on the clock since it began) and has had the radiator replaced and system flush on two occasions. The heater fan is fine but it does not blow hot. At the time of flush the system flowed at the header tank, radiator and heater hoses.
This weekend, unexpectedly the heater worked but the coolant warning light came on as the temp went into the red. This was 50 miles from home. The level was checked and was OK and we managed to get the thing home by driving at a steady 50mph - all the time just skimming the 'red zone'.
It's stumped me. I would have thought if there was something blocking the system then the heater would not work - or at least work hot for a while then cold/warm indicating no flow. Ideas please

[MarkyB]

Sticking thermostat?

[8009STEVE]

Its a modern> Flog it and get a moggie

[MarkyB]

A quick search suggests the the plastic water pump impeller has a habit of coming loose on the shaft.
Some people have changed a lot of expensive stuff before finding this was the issue

[Peetee]

Thanks Marky. Two cheapish problems to take my mind off the thought that it might be the head gasket.

[linearaudio]

Must admit, whenever I've had those symptoms it has been head gasket, but keep your fingers crossed!!

[Peetee]

Furter to previous symptoms. I have opened the header tank and found the level has not dropped more than 300ml. That was probably lost the last time it overheated and coolant was lost to the overflow when I got the header tank cap off. I have topped up and run the car on tickover to running temperature. there is coolant flowing into the header tank and the rad hoses and heater hoses got hot. after a 2 min drive the header tank cap was removed and the level was way up and the system pressurised. I relieved the pressure, 2 min drive again after which the temp guage was slightly up and the coolant system was pressurised again.

[MarkyB]

Sounds more like head gasket then.
Worth checking the other items as anything that causes it to overheat is likely to damage the new head gasket.

[Peetee]

A friend came over to test the head gasket with a colour changing liquid. Couldn't see much difference myself so......
Driving it around to find its replacement it was overheating very quickly so we were sure it was on its last legs. However, this time, the top rad hose was hot and the bottom stone cold so i suspected thermostat. With that in mind i went all out to dismantle as much of the cooling system as i could and check the water pump, change the thermostat and do a proper flush of all areas and got a far bit of debris out of the system.
With everything back together its working fine now.
Will check for water loss as it can only be through combustion now as the system is leak free. I guess the system had an airlock somewhere that moved on and gave differing symptoms. And that airlock could be combustion related so will keep an eye out.
Good to have a positive resolution but angry that three independant professionals couldn't resolve something that an ameteur 'bodger' fixed in less than a day.

[MarkyB]

It's not bodgery if you beat the "pros".
You are now awarded the shade tree mechanic diploma of excellence.[frame][/frame]

Or this one:[frame][/frame]
Both pinched from US sites, hope they don't sue me

[chickenjohn]

It is also worth making sure you use the right antifreeze for your car! If you use the blue glycol stuff that is fine for our Minors and other Iron engined cars. However, in a modern with an aluminium engine or head it can cause blockage problems as the antifreeze, which may contain phosphates can attack the ali head/block causing build up of debris, and possibly blockage and symptoms simmilar to those your Galaxy suffered from.

Go to a Motor Factors (somewhere they know what they are talking about!) and ask for the right type of antifreeze for your car. They are often colour coded, red, blue or green liquids.

Your overheating problems may have been caused by use of incorrect antifreeze!!

some explanation here:- http://www.whitfieldoil.com/www/docs/164.244

[minor65]

I work for a volkswagen dealership here in N Ireland. The diesel engines fitted to the galaxy is from the vw sharan.
They have a plastic impeller on the water pump which through time melts and comes of the shaft. Which causes engine not so much to overheat at early stages, but not enough piff to put hot water through the heater system. I would be 90% confident it is the water pump (timing belt off job).

[rayofleamington]

Without googling I'd have betted as follows:
75% propable water pump
25% probable head gasket
0% probable thermostat.


The reason I say this is that you should have good flow to the interior heater if the thermostat is open, closed or operating normally. If the thermostat is stuck open, the coolant shpld be overcooled giving a cold heater and a cold engine (not a hot engine and cold heater). If stuck closed you'll get a hot engine and hot heater.

I've never had a failed plastic water pump, but have had a failed steel one (no blades from being run without antifreeze) which gave similar symptoms. Also had a pinhole leak at the headgasket (on a 5yr old Fiat) due to a fault in the head casting which gave the symptoms of faulty waterpump / airlock.
On the basis that you're not topping up water despite overheating, I put my money on waterpump.

If you've got some funny piping in the coolant system (which I wouldn't expect) and they've used a steel pick up pipe to vent an aluminium head (like a Volvo with a renault engine... with a vent pipe that can block up with oxides) I expect you'd have found threads about air locks by googling it - if it's got this kind of complicated pipework which can lead to airlocks then that sit's in first place of probability.