coolant is leaking

[rwalker]

Originally Posted by NastyBlackx5

my coolant has been leaking like crazy. I jerry rigged it together, but still notice puddles under the car. i am freaking out, has any had this issue or any advice?

I'd been having the same issue with my 2003 4.4i with 60k miles. Over the course of several months the car would eat a gallon or so of coolant. No white smoke, no residue buildup under the hood.

The problem turned out to be a pinhole leak in the plastic tube that wraps around the expansion tank.

I spent weeks isolating the leak. Finally, it got bad enough that I could see it when the thermostat opened, spraying all over side of the expansion tank.

The part that failed is #8 in the attached diagram. The image is copied from realoem.com at:

RealOEM.com BMW E53 X5 4.4i Cooling System Water Hoses

[rwalker]

Today, I had to fix the leak without access to BMW parts. My plan was simple: clean the hose/pipe and duct-tape over the pinhole until a replacement could be had.

Unfortunately, my plan came off the rails about one minute in.

It went like this: I placed a little hand cleaner on a rag, wrapped it around the thin part of #8 and rubbed gently back and forth. While doing so, I heard a bunch of crackling, then suddenly the pipe broke off in my hands.

The plastic part of the input hose had completely disintegrated. It literally crumbled in my hands.

My first reaction was shock, then horror when I looked around the engine bay and found other uses of the same material. Is this car a ticking time bomb? It's like 1 month out of CPO and all these little plastic hoses are shot!?!

After I calmed down, I pulled #8 above and set about fashioning a temporary replacement. The ends of the plastic pipe have little copper (or bronze) inserts to allow the hose clamps that secure the plastic pipe to the rubber ends to do their job.

I formulated a new plan: strip the brittle plastic from their metal end-fittings, re-use the fittings to join the old rubber ends to a new chunk of 1/4" fuel hose (which I had on hand) to fill in the blanks. Attached is a picture of the result.

[rwalker]

There is some possibly good news in all this. Maybe the rest of the plastic piping in the engine bay is ok...

While recovering the metal fittings from the plastic hose, I was surprised to discover some of the plastic was actually in pretty good shape. Whereas the majority of the hose was so fragile I could crush it between thumb and forefinger, the parts of the plastic hose not exposed to coolant were actually still quite tough.

I'm too afraid of failure to squeeze the fuel return line in my fingers, though. Anyone else brave enough?

[rwalker]

The really bad news....

After fashioning my makeshift coolant return line, I unscrewed the expansion tank cap to top up the system.

When I pulled up on the cap, I noticed that the rubber washer on the very bottom of the cap was hanging off slightly. On closer inspection, I found that the plastic of the expansion tank cap had disintegrated. The plastic lip that holds the last rubber washer on the bottom of the cap had mostly (maybe 80%) fallen off!

Since I'd had that cap off maybe 10 times in the last week or so, I had yet another panic attack: those fragments of cap are likely floating around in the water galleries of my motor!

I immediately removed the expansion tank and flushed it out while being careful to collect anything solid that might be rattling around. What my efforts yielded was saddening: only a tiny fraction of what was missing from the cap was found in my tank.

I can only hope the rest of the cap fragments don't clog a critical gallery, or that the water pump pulverized the chunks before they could do any real damage.

Time will tell.

I have #8 above and a new expansion tank cap on order.

Find attached pictures of the disintegrated cap.

Videos of my situation on YouTube:
YouTube - 2003 BMW X5 expansion tank cap falls apart
YouTube - 2003 BMW X5 expansion tank cap falls apart, pieces recovered from tank


Watch your plastics: BMW did not make these cooling systems to last...

[antonnyc]

wow guys seems to be a common problem.......I think I know what to do first...PRessure test comes first!

[Weasel]

Wow rwalker, your first 4 posts are informative ones, including an emergency patch that any of us with the V8 X5 can use when the plastic hose around the expansion tank breaks. (which I mainly see when someone accidentally rests their hand on it/leans on it on accident)



And I wouldn't lose sleep over the plastic bits from the cap... what you see with your cap is perhaps the most common failure of the radiator cap, and I've never seen a problem caused by the tiny bits of plastic. (my guess is they end up in the bottom of the radiator end tanks) But you will want to get a new cap asap as the seals being in place are important for proper cooling system operation. And when it's all done, maybe treat her to a cooling system flush. She likes that about every 3-4 years or so. .

[rwalker]

Originally Posted by Weasel

Wow rwalker, your first 4 posts are informative ones, including an emergency patch that any of us with the V8 X5 can use when the plastic hose around the expansion tank breaks. (which I mainly see when someone accidentally rests their hand on it/leans on it on accident)



And I wouldn't lose sleep over the plastic bits from the cap... what you see with your cap is perhaps the most common failure of the radiator cap, and I've never seen a problem caused by the tiny bits of plastic. (my guess is they end up in the bottom of the radiator end tanks) But you will want to get a new cap asap as the seals being in place are important for proper cooling system operation. And when it's all done, maybe treat her to a cooling system flush. She likes that about every 3-4 years or so. .

Thanks for the comforting words, advice. I will be giving it a flush (even though it's just had one), and the new parts are on order.

[rwalker]

After replacing the expansion tank cap and return line with new parts and flushing the system (the engine block drain was a real pain in the ass!) the car was leak free for almost a month.

Now, the expansion tank has given up the ghost. It's leaking from the seam, spraying coolant all over the engine bay. Sigh.

The car's mileage has also taken a sudden nose dive (from maybe 15mpg to 10mpg). I've run OBD-II diagnostics on the O2 sensors, they seem fine. I think what's happened is a chunk of the radiator cap (see above) has lodged in the thermostat, holding it open, forcing the car to run rich.

BMW apparently designed the cooling system to fail immediately after the warranty expires: brilliant.