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Old 11-29-2010, 12:15 AM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
Radiator autopsy

I first looked closely at the entire radiator in order to find where it had failed.

It was not easy to see any flaws, which was surprising to me since I had seen water leak out of the driver's side, below the hose, about midway or just above midway on the plastic side. (In hindsight, I should have looked harder while the engine was running; but I just assumed a major leak based on the volume of spray coming out.)

To help me find the flaws, I rubbed chalk over any imperfection I could find.

About the only place on the radiator I could find a flaw was this apparently slight crack on the PASSENGER side (note that it appeared that the driver side was where the leak lay, although there was some liquid at the expansion tank side of the radiator but it could have been thrown there by the fan).

I noticed the only thing holding the plastic side panels in place were an evenly spaced series of crimps. With a pry bar, I easily pushed up the soft aluminum crimps to free the passenger-side panel containing the alleged crack.

Soon the passenger-side plastic panel popped free, along with a rubber gasket along the edge.

I repeated the effort on the drivers side aluminum crimps, which, with experience, came off easier than I had expected.

Soon I had both plastic side panels in my hand. Amazingly, the purported crack I saw from the outside did not appear to extend to the inside of the radiator. I was perplexed. In fact, there were NO CRACKS apparent looking at the inside of the radiator.

At this point I wondered if the failure was on the driver side hose itself, or in the expansion tank. However, I re-used the hose (that hose had been recently replaced with the alternator only a month ago due to my clumsy destruction of the plastic bleed screw during bleeding); and a later post will show no apparent cracks in the expansion tank.

Looking closely at the bottom of the drivers side panel, near the drain screw, I noticed a bit of gray clayish gunk. Not much. But a little gritty stuff around the screw itself.

I noticed the same very thin fine gray paste on the corresponding passenger side panel. (Any idea what this is? Is it aluminum dust?)

After looking the two panels over for fifteen minutes, I finally gave up trying to identify the flaw that caused the coolant leak. Whatever it was, it was minute if it existed in the radiator at all.

As it's important to be able to remove the nipple from the drivers side of the radiator, I took a look at how that nipple socket is constructed. This, in the future, may be useful because we don't yet have a cn90-patented technique for removing the nipple intact, so as to make a radiator shroud removal a dry affair, without the need to replace the expansion tank overflow hose radiator nipple hose clamp in the future.

It's hard to tell here, but it is worthy of note that this radiator nipple was "saved" during removal. This is a Behr nipple bought at the BMW dealership because the original nipple broke when it was removed during an alternator repair a few months back. While the new Behr nipple went in place at that time without problem, it was nearly impossible to remove that radiator nipple without destroying the two tabs on the radiator holding that nipple in place.

What we need is a better mechanism for removing this nipple intact, to facilitate shroud removals that do not require cutting off the original BMW hose clamps.
- WANTED: An ingenious method of removing radiator nipple

It is also important to note that the new Nissens nipple, which came with the new radiator, was much larger in diameter at the bulb end, necessitating a larger hose clamp than was initially expected, and further necessitating a trip to the auto parts store to find a larger solid hose clamp. The initial replacement hose clamp for the Behr replacement nipple was 11-13 mm solid band. The parts store was missing the size in between; they only had the 14-16mm size. The Nissens bulb end needed something in between (lesson learned). I had to grease and tug and pull and coerce the smaller clamp onto the larger Nissens bulb.

I also took a look at how the drain screw works. It appears to snap into place to lock in the closed position. If leverage is required, a small Phillips screwdriver can be inserted into the hole to turn the drain 90 degrees to open it up to the flow of coolant. This appeared to be working correctly.

Lastly, I took a long hard look at the radiator metal itself. I was shocked at how clean and pristine looking the inner flat tubes appeared to the naked eye. They were amazingly clean, considering the car was built in late 2001 and 91K miles had been driven on this OEM radiator (date code verified).

In the future, an enterprising individual who comes up with a method for re-crimping new plastic (or better yet, aluminum) side panels, will be a very rich person!
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Last edited by bluebee; 11-30-2010 at 04:15 AM.
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