AxlRose328ci

Expansion tank literally exploded

19 posts in this topic

I just got back from work which is about a 20 min drive and I was just outside my house with the engine still running then all of a sudden boom, loads of steam, I pop the bonnet and see the whole side of the expansion tank has broke off. Recently had a new radiator about 2 weeks ago, could this be related or just a coincidence? Temp gauge was bang in the middle as normal, it's fine getting a new expansion tank but could there be another problem which causes the tank to blow? Thanks for any help and info.

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pete_h   

Given that your tank has gone, it's worth checking the associated pipework , it's pretty easy to follow if you start at the radiator.

Did a garage do the radiator replacement for you ? If so I would speak to them and see what they say as a starting point.

Thankfully it happened outside your house and not on the road , miles from home.

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alan53   

have you considered a change to a 1.4 bar radiator cap it hopefully wouldnt have failed so dramatically ?

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I replaced it with a mate of mine who also loves an works on bmws, we checked everything over. Could we have bled the system wrong? We changed the thermostat a year or so ago and had no problems. Never heard of a 1.4 radiator cap, please tell me more, Thanks.

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Could have been air pressure build up i guess but they are weak anyway just get a new one ordered and wang it on. my friends 330 blew its cap when the pump failed but if your sure it didnt overheat then no worries!

Sent from my GT-I9500 using Tapatalk 2

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alan53   

As i understand it it from reading US forums it would release the pressure earlier so a car would overheat but hopefully before breaking something usually plastic and spilling all the fluids and giving time to take action ,also the cooling system is not able to stand pressures alot higher than 2 bar.

I am currently running a 1.4 bar cap no fluid loss or problems.

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Marcus   

its quite common for expansion tanks to pop .

according to my dealer they recommend a change at 100k. the new ones are of a better design. I bought oe .

don't panic about anything else imo

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bungers   

They're a weak point on the e46 (never seen a diesel one go though, probably due to the lower running temps). Replace it, bleed the system & you should be fine.

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mjn   

Mine went at about 150k.

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By replacing the rad you the pressure build up in the system just finds the next weakest component, in this case your expansion tank. Very common.

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BmEagle   

As above, my expansion tank on my old 318 went bang. Changed. A few weeks later thermostat housing started leaking. Changed. Few weeks later water pump went spectacularly on motorway. Changed. Couple of months hassle free then rad springs a leak. Budget allowing unless other parts have been replace already is do the rad, tank and water pump. Will save you long term for replacing coolant 3 times and the time and hassle.

You've done the rad so only the water pump left to do.

Edited by BmEagle

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Ive replaced the expansion tank and cap and proceeded to bleed system but it looks like its only filling the expansion tank up and not the engine, thoughts?

Edited by AxlRose328ci

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I had this when I first got it 2 days after owning it the radiator blew catastrophically blew the top off and blew the bottom clean open all the way along, I put a new rad on in my driveway after bleeding twice from clips not being on properly on piping (working in the dark on a driveway I guess) I did it again but didn't turn the heater up while bleeding, about a week later I put the heater to full, air worked its way out of the matrix and locked down the piping causing the pressure to build and blow the expansion tank apart! Ball ache to say the least...

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I've checked the coolant level each day when i'ts cold and the level does seem to have dropped slightly, so I think there may be air trapped still. I went for a 20 minute drive and everything seems good with the coolant temp maxing out at 97 degrees which I think is fairly normal from what I've read on here.

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stevewav   

I know this is an old thread but I wanted to add my experience as it might help someone else as well.
My tank exploded as well while driving away from the school where I leave my kids in the morning.
There was snow everywhere and the temps bellow 0, and I was stuck in the traffic as the roads were not in the ideal condition...
All of the sudden I heard that awful noise and a lot of vapor started coming out of the engine bay.
The engine stalled but as I was just about to enter the roundabout with lots of cars behind me I had to restart it an move away.
Anyway I did some 100m without any water in the engine knowing I could do some irreparable damage to the engine but I could feel the frustration of the rest of the drivers behind me if I had decided to stay there....
The expansion tank had opened as a banana one one of its sides and the level indicator had disappeared.
I was pretty lucky to find a replacement part at the dealer as they usually need to order the parts here in Luxembourg.
It was a real PITA to get the old one out of there as the bent part had overcome the bottom security latch and was bushing against the inside of the part...
Anyway I managed to get the piece out and replace it.
I started refilling with coolant and surprise surprise the side tube was leaking. It was then that I realized that there must be an internal O ring that is now missing...
I have a set of various sizes of those at home so I found a similar size match but not the exact one (20x3 original, 20x2 mine).
At first I thought I was OK as the tube gave me some resistance going in but I was once more wrong.
The resistance was due to the fact , as I found out later, that the O ring does not stay in place when the tube is bushed in but it gets out of its place and of course it is ruined.
Silicon grease gave the solution to that problem. I resumed the refilling process and no leaks this time.
With the system full of fresh coolant I started the engine and waited to get worm in order to release the air from the valve, but for my surprise once more, I had tons of vapor coming out instead of air or coolant stream.
It was then that I realized there must be something else that doesn't work properly.
The day after I decided to restart the possess but with the help of my handheld scanner this time so that I can monitor both temperatures (engine and radiator outlet).
This time I was able to see the temp rising over 100 degrees but the electric fan did not engage !!!!
resetting the plug solved the issue but it was then that I realized that probably because the fan had stopped functioning the engine while at school had created a lot of vapor inside the engine that created so much pressure and caused the explosion of the expansion tank!!!
Unfortunately there was no warning, no overheating nothing that could have prevented this, so my advise is to regularly check that the fan is engaging from time to time, as the contacts with the age might become loose....

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