Cooling syst. Water expansion tank. ?

[herbiemercman]

Hi Guys, The white plastic expansion tank in front of the radiator, as most of you must know it has a low and high mark moulded into the LHS of the tank. There are two rubber pipes one positioned towards the bottom of the tank and the other short pipe bends down 2 inches outside the tank, this is obviously to run off excessive coolant for owners who have over filled the tank, the inside pipe must take the coolant from expansion volume as the engine heats up, and also provide feed back coolant to the system where it is required?

For the 22 years i have owned the car from new the red coolant, (OEM for life) has always sat at the lower mark when the engine is cold and at the upper mark when the engine is hot, i assume this is the normal function?

When my cylinder head gasket failed in recent months on cylinder no1 was the first time i experienced the loss of coolant and i badly pluming exhaust, i also carried out a test on the coolant and it clearly showed combustion products in the coolant, i was sure it was a failed gasket.

Following the new gasket replacement i filled the cooling system and bled the top hose to the heater on the bulk head, the expansion tank was filled to the very top, i have covered some 40 miles at moderate speeds car running perfectly, the cooling liquid has now settled at the lower mark on the tank with the engine cold, am i right in assuming that the air bubbles etc have expelled and the system has returned to the normal operation? Herbie.

[Scooter]

My expansion tank always seems to be down lower even if I refill. As you are understandably cautious following the work, I would remove the rad cap every time you go to start it from cold and as long as that's full to the brim and there is something in the expansion tank that would be good enough for me.

[Dnk]

I run the engine up to temp with the rad cap off to get all the air out, when the

stats opened set the heater on max temp and fill up the rad to the top and fill the overflow

tank to the max

 

As Scooter says just keep an eye on the rad level when its cold and obviously the tank

level as it might just need more running to be fully bled of air which it should do just

by driving it

Edited August 2, 2019 by Dnk (see edit history)

[PJJ]

Mine also rests at the minimum line, even after I've topped it up to between min & max on odd occasion thinking it was slightly low. Radiator is always brimmed full to the top whenever I check the by taking the cap off.

So I just assume that the natural level of the system settles itself to the minimum line on the expansion tank.

[herbiemercman]

Thanks Scooter & Dunk & PJJ, Yes that covers basically what i have done i am confident it will be ok. I just got a bit paranoid following the initial hall marks of the failed gasket, loss of water and heavy pluming. A head gasket failure is a real expensive "balls ache" and i am an HND Engineer and cannot stand oil leaks, water leaks, things that do not work etc. Herbie.

[PJJ]

You're welcome Herbie.

 

Always find it's best to be a little paranoid, inquisitive, let's fix it now before it gets worse etc. (I'm the same with also being an Engineer at Bentley Motors). That's the best way to ensure you're car is maintained properly. The amount of people you see who seem to think it's ok to leave a leak until they get around to it, then after a while they're asking how to fix a more serious problem.

 

Happy motoring mate, sounds like you're enjoying the mods you've done.

[Dnk]

Thanks Scooter & Dunk & PJJ, Yes that covers basically what i have done i am confident it will be ok. I just got a bit paranoid following the initial hall marks of the failed gasket, loss of water and heavy pluming. A head gasket failure is a real expensive "balls ache" and i am an HND Engineer and cannot stand oil leaks, water leaks, things that do not work etc. Herbie.

 

[Tyson]

Mine has always sat at the maximum mark for the entire time I have owned and this is where all my other cars have sat to. For my new cars the manufacturers always fill to the max mark both when picking a new car up and when taking it for a service but as long as it isn’t empty you’ll be fine.