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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 12-17-2011, 09:45 PM   #1
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Join Date: Jan 2009
Location: USA
Posts: 11
My Ride: '02 BMW 325i
Post $-DIY E46 Radiator leak FIX!-$

OK! First off I want to say I took a lot of pictures, maybe too many...
They say a picture is worth a 1000 words so maybe a 1000 pictures is worth a million words?

Anyway this little FIX only addresses the specific leak problem I ran into when swapping out a radiator.

A little American ingenuity & a $4 expandable freeze plug saved me buying a $600 Radiator (dealer price)

On Manual Transmission models the design of the left radiator tank leaves an opening to the cavity of the radiator tank near the bottom that is only blocked by a plastic stem with an O-ring. ONLY this seal keeps your antifreeze from just running out of the radiator tank onto the ground!
This circular opening resides on the driverside radiator tank just above the draincock. This opening is where I had coolant leaking out of!
(See Green arrow in pictures below).

When I installed my replacement radiator tank I had bought some time ago coolant poured back out onto the ground!
Now It was a working salvage I had got on the cheap. The guy was parting out a BMW cause his son had gotten T-Boned in it.
The front of this car was immacualte & I watched him drain the A.freeze & Remove the Radiator... So I know it was a good one!
Immediately I get online and start researching the problem. Apparently I am not the only one who has experienced leak problems that involve the Radiator Adjustment Screw. Under no circumstances ever turn the HEX that holds the blue drainplug! If you, or a Mechanic trying to flush you system has done this, then this repair will not address your problem I have not turned this! Still Worried Tho! Because from what I've read even if you replace that part called the Radiator Adjustment screw. It still leaks! Turning it seems to break something! I confirmed this on my old radiator.

Then I realize the Bimmer I got the Radiator from must have been an automatic. Looking at all the Images of Automatic and Manual Radiator Adj Screws. The one for the Automatic is longer. The Manual one is Short like I took out of my origional old radiator. AhHa! I dont have a trans. cooler and the replacement radiator has the Long Radiator Adj Screw. If you look at the pictures you will see the problem. With that configuration there is a channel open to that part of the tank where that hole resides for a cooler! I gotta PLUG that HOLE! And thats exactly what I did! Worked like a charm!

BTW the dealer tells me this is not fixable,,, come buy a new radiator.
My BMW Dealer parts guy also tried to tell me about BMW spending millions of dollars R&D and that design is there for a reason and the radiator needs to breath or something Come On! Its a closed system! if it breathes from the bottom your antifreeze will be on the ground. period! Even he did not realize what the actual problem was.

NOW I took my old radiator apart to see how it was designed! You'll see this in the pictures.

PLEASE NOTE I never removed the tank on the good radiator! Nor the Radiator Adj Screw! But I am convinced it has the Long Ver. of the Adj.Screw

This fix will not work if you have the short Adj Screw! The short one has no bottom seal! What a stupid design!

Some of the pictures are for providing insight into how the tank is designed.

See pictures below.

Due to problems uploading so many pictures I'm gonna put the bulk of them on Photobucket!

http://www.photobucket.com/bmwradiatorsleak Click view as Slideshow
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Last edited by RajunCajun; 12-21-2011 at 06:54 PM.
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Old 12-17-2011, 09:46 PM   #2
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Join Date: Jan 2009
Location: USA
Posts: 11
My Ride: '02 BMW 325i
By now you should have viewed about 40 pictures.

To sum a few things up. I plugged a potential leak point on the E46 radiator left by the Manufacturer!

Now in the picture showing it installed back into the car when finished - Please note I spilled a lot of antifreeze bleeding the air out of the system!
The green drops everywhere are from the bleeding process but you will note that the Effected Repair is Bone Dry!

The plug was longer than I liked so I modified it shortning it by approx 1/4 inch. Making it nearly flush when bottomed out in the hole against the stem of the Radiator Adjustment Screw.

Also at first I tried to use RTV Hi Temp Red Permatex when installing and tightning the plug... Dont Do this it makes everything so slikery that you absolutely cannot keep the plug in the hole and tighten it down. It would actually squeeze itself back up out of the hole. Funny to watch but irritating as hell. Must have friction to tighten and hold in hole so i had to clean it all back off and then it worked like a charm!

Do not over tighten. I was afraid of busting out the side of the hole. So I was modest when tightening this up. Use your best judgement. Dont go Nuts here!

I noticed on some other posts about the E46 radiator that BEHR makes an aftermarket radiator for this car with no hole or even drain plug in this spot. So I see no problem doing this to my radiator! Looks like im not the only one that feels that was a stupid design!

The rubber part of the plug cuts much easier than I thouht it would, so be carefull just dont cut yourself!

O' and yes thats a New OEM BMW Coolant Reservoir. $87 w Tax from the dealer. I found cheaper online but not in town.
Also replaced VCGasket, Oil Filter Housing Gasket, Idler, Tensioner, Alternator bearings, New belt, New Filter & FullSyn OIL,New NGK's,
Air Filter, Powersteering tank Cap O-Ring,,,, and Cleaned Motor.. FEW!
Back on the road and No More Leaks! Holding Normal Operating Temp!

Thank God thats over! Did all the work myself after work and on weekend! The dealer would have cost me Thousands to do all this! I'd say I spent approx $350-$400 dollars I havent added it all up but thats close! She is much quieter with the noisy bearings in the belt drive systems replaced too, No more cutting the car off at drive up windows because of embarrasing noises! I've got that new car sound again!
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Last edited by RajunCajun; 12-21-2011 at 07:01 PM.
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Old 06-01-2012, 11:11 AM   #3
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Join Date: Mar 2011
Location: U.S.A
Posts: 235
My Ride: 04 E46 330i sport
this is what happened. Now how do i fix it?
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Old 05-19-2014, 11:43 AM   #4
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Join Date: Jun 2007
Location: Auburn
Posts: 93
My Ride: BMW 323i
I know this tread is old but I had the exact same problem with a brand new radiator and it had the correct radiator adjustment screw so I have to put a plastic plug in that hole and problem solved. I totally agree that this is a such a stupid design, they should make a no hole radiator for manual and a hole radiator for automatic and bye bye radiator adjustment screw. Also a full aluminum would make this last longer... anyway...
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