E34 535i - Cooling system over pressurising?

[0llie 0]

Hi all

My e34s cooling system doesn't seem to be releasing pressure after the car has cooled down. The pressure causes coolant to leak out around hose clamps (they are super tight) and other areas..

The upper radiator hose is firm with pressure when the car is cold. I thought the radiator cap might be the cause so I. replaced it with a brand new one. Due to the leakage I get the coolant light coming on sometimes. I slacken the radiator cap (when its completely cold) and usually I get a bit of coolant returning to the expansion tank.

Just wondering if anyone else has this problem and how they've fixed it.

Cheers

[javlin 0]

I sincerely hope for you that your waterpump is not on its way out. Our's failed recently resulting in a major engine overhaul. The car had been using some water which set off alarm bells but the fault wasn't traced to the waterpump until too late. The pressure blew a hose on our car.

[BM WORLD 1283]

maybe head gasget leak causing over pressure , but fix any leaks first as they will let air into the system and cause similier problems , had same issue with my 535i recently ended up being a head gasget (sleight corrosion after 20 years)

[kiwi535 538]

maybe head gasget leak causing over pressure , but fix any leaks first as they will let air into the system and cause similier problems , had same issue with my 535i recently ended up being a head gasget (sleight corrosion after 20 years)

ditto although i beleive in my case it was just many many heating and cooling cycles between disimilar materials(iron block,alloy head).I beleive the car has always had fresh coolant,certainly in the time i have had it,but it went anyway,similar symptoms to yours,using a bit of water,hard hoses after cooling,misfire when starting.I tried releasing the pressure via the rad cap as soon as car has cooled a bit.No misfire when starting...that was the clincher for me

[0llie 0]

Thanks for the replies bugger I forgot to tick the reply email notification.

I've gone through and tightened all the hose clamps.

Its a little hard to figure if its using water because with the pressure still in the system it causes leaks when the car is cooling down, even when the hose clamps are tight as. It starts leaking around the transmission hose washer underneath the upper radiator hose on the radiator.

I'd like to know if anyone else's upper radiator hose is firm (like really firm) when the car is completely cold? Its not like that on any of the other cars that I've owned, the pressure usually disappears when the car cools down.

[kiwi535 538]

Thanks for the replies bugger I forgot to tick the reply email notification.

I've gone through and tightened all the hose clamps.

Its a little hard to figure if its using water because with the pressure still in the system it causes leaks when the car is cooling down, even when the hose clamps are tight as. It starts leaking around the transmission hose washer underneath the upper radiator hose on the radiator.

I'd like to know if anyone else's upper radiator hose is firm (like really firm) when the car is completely cold? Its not like that on any of the other cars that I've owned, the pressure usually disappears when the car cools down.

i am afraid that you have a blown h/g.The hard hoses are a result of the system being overpressurized.if you keep doing it you will also blow the rad.Mine was like that.when the car has cooled a bit you can release the pressure by loosening the rad cap.The trans line leak may be a small crack in the connection of the trans line spigot to the radiator tank

[Eagle 1662]

+ 1 for the headgasket. Noticed my coolant level down and hard hoses a few days ago too, replaced the expansion tank cap for a last resort but knew it was a long shot. Car done over 500,000 and been looked after but nothing lasts forever.

[mr E34 11]

Also make sure the thin hose leading to the expansion tank isn't blocked, fairly common problem.

I regularly squeeze my top radiator hose when cold to listen for the float bobbing up/down in tank.

[0llie 0]

Just wondering if it was head gasket, the car has been driving around with this problem for about 30-35,000km. Also haven't noticed any milky or sludgy oil during oil changes. Would I have noticed this if it was a blown head gasket?

I'll check thin hose going to the expansion tank. Did read on he internet about them tending to block and a website suggested to enlarge the hole slightly which I did.

[Eagle 1662]

Get a leak down test done, that will tell you.

[Jo Blogs 11]

Get a leak down test done, that will tell you.

Get a T-Kay test done, This checks for combustion gases in the cooling system.

[gmccormack 0]

Just wondering if it was head gasket, the car has been driving around with this problem for about 30-35,000km. Also haven't noticed any milky or sludgy oil during oil changes. Would I have noticed this if it was a blown head gasket?

The gasket may have failed or a crack formed between the combustion chamber and water gallery only, so you don't necessarily get any oil contamination. Sometimes electrolysis can open up the water gallery until there just isn't enough cylinder head for the gasket to seal against anymore.

[kiwi535 538]

i did not have any symptoms of a blown headgasket aprt from;Miss at start up,firm hoses after a long period,slow use of coolant