My E46 Expansion Tank Mini DIY

If you're interested, there's a Behr expansion tank autopsy here:
- Behr radiator and Behr expansion (aka surge) tank autopsy (1) (2) & request for another autopsy (1)

Starless - My ET started leaking from a hairline crack. I want to replace it but not not all the components yet, I plan on doing those in 2 months. And next weekend I'll be taking the z out.....

I have a '01 Auto 325i. You emptied the ET --> how much coolant did you need to fill it back up after the install?

Thanks

- Sud

Originally Posted by Saranaz4

Starless - My ET started leaking from a hairline crack. I want to replace it but not not all the components yet, I plan on doing those in 2 months. And next weekend I'll be taking the z out.....

I have a '01 Auto 325i. You emptied the ET --> how much coolant did you need to fill it back up after the install?

Thanks

- Sud

I do not remember exactly Just buy a gallon of bmw coolant ($20) - you'll need it later anyway, and use whatever the amount will go in...Mix may be a 1/4 gallon 50/50 with water first and see if it's going to be enough, if not - mix another 1/4...It's been awhile, I forgot...

I know this is old thread. It is a very useful DIY for E46 with AT. I am going to replace the ET this weekend for my 325i 2001 AT. It starts to leak now.

This DIY starts with unplugging the transmission cooler. But my car also has a blue plug. Should I loose this plug first to let the most coolant out? Other DIY I read often mention two blue plugs. My guess is those two blue plugs are for MT cars. For AT cars, it has one blue plug and the cooler to get rid the coolant. Am I correct? If this is correct, can I replace the ET without unplugging the cooler? Thanks.

Originally Posted by harryhchen

I know this is old thread. It is a very useful DIY for E46 with AT. I am going to replace the ET this weekend for my 325i 2001 AT. It starts to leak now.

This DIY starts with unplugging the transmission cooler. But my car also has a blue plug. Should I loose this plug first to let the most coolant out? Other DIY I read often mention two blue plugs. My guess is those two blue plugs are for MT cars. For AT cars, it has one blue plug and the cooler to get rid the coolant. Am I correct? If this is correct, can I replace the ET without unplugging the cooler? Thanks.

No, removal of cooler drains the tank. One blue plug drains the radiator. If you unscrew just the plug, your ET will still be full of coolant. On MT there is the 2nd plug that drains the tank. On AT you need to remove the cooler to do it. It takes 10 seconds to remove it, but be careful, the plastic of the radiator is brittle, do not force it out or you can damage the plastic part of the radiator where the cooler attaches.

And do not worry about bumping "old" threads, that's what these threads are for...

Thanks Alex for your explanation. Now everything is disconnected and out, except the tank. Looking at the big O-ring at the bottom of my new ET, I know I will need a lot of force to push it out. A lot of force but gentle enough not to break the thermometer!

Use gentle leverage to pry it out, works like a champ. Pry bars are your friend. eric

Which part do you pry at?

I read that one fellow put the ET cap on and use it to pry to get it out. It worked for him but not me :-(

Originally Posted by harryhchen

Which part do you pry at?

I read that one fellow put the ET cap on and use it to pry to get it out. It worked for him but not me :-(

It has been a long time since I did this (early '11) and since then I am fighting cancer and am on chemo (today was a chemo day) so I really don't remember, but with all due respect use your common sense when you look at it, you will figure it out.

First you need a complete set of swap meet pry bars then be patient and study the entire layout of the problem from every angle. I am a mechanical engineer by education and common sence but that is not my practice - I am a salesman.

Just be gentle and LISTEN for creeks, tweeks, binding and least of all cracks - take it slowly. When you use leverage you must move slowly because your angle ratios are compounded and movement happens really fast. After the first one popps off and you have that success it will all click for you and it will become second nature.

Good luck and be patient.
eric
sorry no pix of actual prying word applications....

Originally Posted by harryhchen

Which part do you pry at?

I read that one fellow put the ET cap on and use it to pry to get it out. It worked for him but not me :-(

Actually Smolck does it by lifting the car, positioning a jack stand under the expansion tank and GENTLY and CAREFULLY lowering the car just a little allowing the jack stand push the ET out. I've never tried it myself but it makes sense to me. But please be careful if you try this method.

When I did it, I used prying, using a screwdriver and a hammer, pulling from top, etc...Just being creative I guess for like 20 minutes and the tank came out. I did damage it a little when removing by hammering on the screwdriver but I was not going to reuse it anyway, so it did not matter to me...

Good luck!

I am sorry you are ill, bernoccoZHP. Best wishes from me and hope you will recover from it soon.

Thanks Alex. I guess I will try out all the approaches to see which will work for me. Maybe I will put up a quick summary for it. Luckily, I don't need the car for my daily driving.

Hi Alex,

I managed to remove the tank. see my link: http://www.bimmerfest.com/forums/sho...d.php?t=588883

But the thermometer cover tilted towards left (see the picture). Is it normal or should I resit it? Do you know how to remove it? thanks.

What is a expansion tank.

Thank you! Great photos so if i cannot get a guy who knows what to do, i can do it myself. My car has over 100,000 miles so i guess the leaking problem should be expected. Thank you, again...

To answer your question....the expansion tank is where the extra fluid goes when the system builds up pressure as it gets hot

with your car cold, turn it on. take the coolant fill cap off. when the car warms up SOME you will see the fluid rise and want to spill out of the filler hole..this is the pressure build up that forces fluid into the expansion tank when the system is sealed....put the cap back on before it spills out too much. DO NOT DO THIS WITH CAR WARM....IT CAN/WILL BURN YOU SEVERELY

in a sealed system, where is this coolant that wants to spill out going to go? its sealed so it has to go somewhere or it creates problems in hoses leaking from the pressure buildup. The fluid goes into a tank next to the radiator.....which is the expansion tank.....as the car cools, the pressure created from the heat when the car warms up turns into vacuum and pulls the fluid back into the radiator and out of the expansion tank.....This is much more simple and reliable on cars dating back to the first cars ever produced all the way up to most cars even now. bmw way over engineered this system so they could sell you parts later...like every 100,000 miles....no cooling system ever has to be designed this complicated

on all my muscle cars...with the old system. They break.......never... my 79 trans am's expansion tank is a killians mini keg with a hose going to a nipple under the radiator cap....its really that simple of a system....if you want to find out what it does....there should be a simple diagram online. unless you were joking with the question....but good for a noob

Tank came right off with a few taps from below. BUT, I noticed that the plastic cap that holds the thermostat and spring on broke the ears it holds onto, not the cap, but the Plastic piece the springs sits in and cap "twists" onto. Is this considered the thermostat or is it called something different?

Thanks in advance,

Robbie

Thanks Starless for the DIY post!!! It was very useful and the pictures made replacing the expansion tank a breeze.

My tank busted on the way up to a camping trip this weekend. I had my car towed home and had to rent a car to salvage the remainder of the trip (BMW was closed on the weekend). Then on Monday I got the job done in a short while. I took about 3 hrs becasue I took my time as I didn't want to break anything and I'm not savy with the mechanical skills.

Something I would like to add is a trick my buddy (BMW tech) shared with me. When you put the new tank back in, use silicone paste lubricant on the radiator and new tank fittings. The hoses and clips easily snap into place. He said this is how they do it in the shop to prevent breaking things or rolling the o rings. It just makes it easier to snap everything back into place.

The exact lubricant he uses is below:

http://www.amazon.com/3M-Silcone-Pas...Silicone+Paste

Brown fern, thank you for the link, looks nice a really nice product!

This is a great DIY, I just had Indy do complete coolant refresh on my mine in Feb this year. Have 71 k now. I now have a coolant leak somewhere. Seem to have white powder on top of ET just under hose or it may be the tank itself. It's good to know that I can just drain tank instead of the radiator to replace tank and upper hose to hopefully fix this small leak.

It's definitely not the cap since there was no white residue on the neck.

I have one question I see there's o rings on auto cooler , did you replace those? Tks!

Edwagon, I actually replaced those o rings but it's funny cause the cooler sprang a leak with the new ones so I put back the new ones and no leak. Makes no sense but sometimes this is how things are :-)

Correction: put back the Old ones

Ill have to see if the Bentley manual has as good of a description of this job

I have coolant leak on my 2000 BMW 323i. I pulled out the expansion tank today following the posts on this forum. However, I don't see the transmission thermstat that I've read about, that mounts at the bottom of the expansion tank. When searching on the Internet, I can only find "automatic transmission Thermostat".

My question is, does the manual shift 323i have a thermostat?

Thanks for your answers in advance. -Frank

I had an equally tough time getting the old tank out. No amount of pulling from above and banging from below budged it. What I finally did was to wrap a loop of baling wire around the tank, careful to go underneath hoses. I put a 2 X 4 across the radiator support and slipped a crowbar under the baling wire. With plenty of leverage, I jiggled and pulled for about two minutes and the tank slipped right out.