rise in coolant level

Hi all,

There are no stupid questions, so here's my stupid question: I noticed the coolant level in the expansion tank of my 2004 MG TF 160 VVC (± 75.000 km) has risen to about an inch above the max indicator when the engine is at (normal) operating temperature – when I open the boot lid after a ride. The level gets back to normal (max) in about 15 minutes. I'm aware of the fact it is called an expansion tank, probably for a reason, but is it for that reason? For the reason that coolant expands when hot? Or, and that's my fear, is it an early symptom of the dreaded head gasket failure and is pressure from the combustion chamber finding its way to some coolant bore? As far as I know the car has its original head gasket. It drives, sounds, behaves absolutely wonderful.

I've asked Google of course and the consensus seems to be that coolant does indeed expand when hot, but by that much? The "hot" level is about halfway max and the top of the expansion tank…

Maybe I'm just suffering from HGF anxiety…

Richard

You are probably worrying about nothing, but for your piece of mind you should pressure test the cooling system and do a compression test.

Cobber is correct, however there are kits that test for exhaust gases in your coolant. These are available via e-bay for less than £15, which is cheap money for peace of mind (or to cast you into the depths of despair if positive).
Head gasket tester sniff tester should bring up one or two types.
M

Thanks both. Found a Dr Head Gasket tester , for instance. I don't have a pressure tester, but the workshop probably will have one. I'll pass by and have my regular mechanic pressure test it…

And well, HGF isn't the end of the world, it's just the end of the world for the present head gasket

Richard

A very philosophical outlook. There are a good many used parts on my car which have been considered redundant having been associated with a motor with a duff head gasket.
I’m glad of the myopic outlook of these ex owners, as my car improves in comfort, speed & facility with each addition. On Thursday it had a fixed steering column, today it has an adjustable one.
I now have to wire it up!
M

A rising coolant level when hot can also be just air in the system, but a combustion gas check will decide the matter.

Hi David, yes thanks, but I very recently spent a few days bleeding the cooling system after screwing on a new header tank cap. Richard, my former official MG-Rover mechanic said, Richard, you should really bleed the cooling system. So, rad, heater, no wait, no coolant whatsoever, blocked, poke with a wire, ah, there it is, and coolant rail, no wait, that one's stuck, yep really stuck, even the hexagonal socket wouldn't get it to turn. But maybe I was just too worried to break something. I left it overnight soaking in penetrating oil, and the next day, lo and behold, it budged. First cold, then hot. Not a single bubble :woohoo:

I first tried to reach the bolt on the cooling rail without taking the "bonnet" off. Youtube Man managed to do it that way. Not me…

I drove it to Orléans today, six hundred something kilometers, with rock steady temp needles – and lots of rain.

Richard

IIRC the coolant system holds ten litres, if we assume a sixty degree temperature rise the coolant will expand by 128cc’s. Engine temperature is probably nearer an eighty degree rise other parts less.
I had an opposite problem on my Skoda, although the coolant level was correct on cold mornings the low coolant light would come on, if I drove just a few hundred yards then stopped and restarted the engine the light would go out.

According to Millersville University – a pdf, look for example 8 on automobile radiator, pp. 23-4 – coolant has an expansion coefficient of 4.0x10^-4 (C^o)^-1. They go on to calculate that in a coolant system of 15 quarts (14.2 l), when the coolant heats up from 6 to 92 degrees Celsius, the spill into the expansion tank will equal 0.46 quarts (0.44 l), which would be about a 3% expansion? But that obviously depends on the type of coolant used… On CarAraC it says some coolants may expand up to 8 to 12% at 100 C^o, about an average coffee cup?

Concerning the Skoda, if coolant expands and shrinks just like any other liquid, maybe the drop in level just made the sensor trip?

Richard

I hope you stay with the Forum as you definitely have the right approach as Airportable commented.

Theres probably nothing seriously wrong but even if so, the parts for a head gasket change are less than a dinner out with the Mrs, a few hours weekend spannering and a great sense of achievement

If you do a pressure test it is important not to over pressurise the system beyond its normal operating pressure of 1 bar. If you go over you risk breaking the bond on the elastomer head gasket if you have that type fitted, thereby inducing head gasket failure. Don’t ask me how I know.
Nigel

No worries, I wasn't planning on going anywhere. I have two Sunstorms, both 2004, both nightfire red, the one 135 (RHD) the other 160 (as far as I know the only LHD), and even if they have proven to be quite reliable, this forum – and, to be honest, the MG-Rover one – have proven to be a valuable assets to keeping these cars on the road – and dry :woowoo:

Today we did Orléans to Beynac,430 km in a horrendous downpour that lasted for hours, motorways like riverbeds, even the French slowed down, no really, except for white vans of course, and no water ingress whatsoever! Not a drop seeping from the cheater. Bone dry. Would the adapted heater air intake, the petrol lines inserted in the door rubbers, hours and hours of fiddling with window adjuster bolt and nuts finally have worked?

This thing goes up motorway climbs like stink…

Richard