Dreaded N62 (4.8i)Coolant Leak - Merry Christmas

[jeremym]

Originally Posted by TwinTurboGTR

All N62 motors are susceptible to the Valley Coolant Pipe leak. Why it was made to be unserviceable is beyond me. As for coolant changes every 2 years doesn't necessarily make you bullet proof against a leak. It's just a matter of odds.

I agree with your last two statements. The *only* thing coolant changes would do is ensure (but still not 100%) that contaminants are out of the system and flushed with new fluid. However, I still don't think that matters as much as the odds, as you say.

[x5745li]

Originally Posted by jeremym

I agree with your last two statements. The *only* thing coolant changes would do is ensure (but still not 100%) that contaminants are out of the system and flushed with new fluid. However, I still don't think that matters as much as the odds, as you say.

The coolant pipe problem occurs because the end of the pipe has a rubber gasket fused onto an aluminum alloy pipe. When coolant is not serviced the ph of the cooling system becomes more caustic. This causes the pipe decay and thus the leak to happen.

[jeremym]

Originally Posted by x5745li

The coolant pipe problem occurs because the end of the pipe has a rubber gasket fused onto an aluminum alloy pipe. When coolant is not serviced the ph of the cooling system becomes more caustic. This causes the pipe decay and thus the leak to happen.

So you're telling me the amount of heat cycles, coolant movement, weather (humidity, temperatures, corrosion, etc.), ambient temp, and other factors don't have anything to do with the issue and that coolant flushes every two years will almost guarantee you never see this issue? I'm sorry, call me a cynic, but I don't buy it.

[x5745li]

Originally Posted by jeremym

So you're telling me the amount of heat cycles, coolant movement, weather (humidity, temperatures, corrosion, etc.), ambient temp, and other factors don't have anything to do with the issue and that coolant flushes every two years will almost guarantee you never see this issue? I'm sorry, call me a cynic, but I don't buy it.

Have you seen what the pipe looks like when it falls apart?
I fixed two of my friends cars with the dreaded pipe problem and
decay of the metal is what caused the failure. Both of them did
zero maintenance on the cooling systems, which is what most people tend
to do on the system.

[TerminatorX5]

subscribed

[gregg3gs]

Sounds like I will be joining the club soon. Six months into this thing and I had to top off the cooling reservoure three times.

Does any one know what parts need to remove to get to this thing (pipe), and whats the best way to confirm this a 100%?

[x5745li]

Make sure you pressure test system when cold (cold shrinks all seals). Could be hoses under intake manifold, Pressure cape, water pump, ....

[Blue4.8is]

Curious as to what happens after the coolant leaks into the valley pan, where does the water go after that?

[95wildtt]

When mine was leaking a year ago, the coolant would pool in the valley pan and only occassionally did it get to a high enough level to run down the back of the engine. There were some stains/traces of the fluid left as evidence.

When it did this, it would usually get boiled off by the heat/exhaust and never made it to the ground. So, I never had a puddle under my SAV, but could smell the coolant after driving...

It's a slow leak, as has been mentioned previously.

[Alamento]

I figured I'd post some info regarding the replacement of the valley pan and coolant pipe on my 2007 BMW X5 4.8i. 125,000 KM.

Last winter the vehicle started to lose coolant. It wasn't showing up as puddles in the garage, but the coolant level warning came on a couple of times. When it did, we took it to the dealer and then topped up the coolant at no charge, and said it was common for these car in the winter. I'm in Canada. The car was in a heated garage both at home and at work, but it gets cold here.

This past summer some puddles started showing up on the driveway. They increased until a couple of months ago, when it started to really pour out.

The dealer's diagnosis was "Upper cap and seal". They quoted me 40 hours labor, parts not included. More if the pipe was leaking.

I decided to buy the AllGermanAuto expanding coolant pipe and a new valley pan and do the repair myself. It cost me approx $1000 US, which is $9000 less than the dealer quote.

The attached image shows my engine with the intake manifold off. My valley pan was leaking. The green arrows show where the coolant pooled at the sides. If I parked on a slope, or when the leak overflowed the grooves beside the pan, it just spills down the back of engine, to the skid plate, and then to the ground.

It didn't appear that the coolant pipe was leaking, but if rubber seals on the valley pan were failing, I figured the seals on the pipe were probably heading in the same direction. When I cut and removed the pipe, the front seal just crumbled away and the pipe was corroded underneath the seal. The instructions that came with the pipe were easy to follow. It took approx 8 hrs from start to finish. I restore vintage (50's) air cooled Porsche/VW as a hobby, and do general maintenance/repairs on the BMW and Audi I own.

Here are some tips for those who want to DIY.

1) The intake manifold is plastic and very light. If it takes effort to lift it, something is in the way. There are 3 plastic electrical connections on the back of the manifold. You'll need to disconnect them after you've lifted the manifold a little bit. They are not long enough to lift the manifold completely off while connected. There's a ground wire going from the block to the fuel rail on each side. Find them and disconnect before trying to lift the manifold. There is also a metal bracket off the driver's side rear stud that needs to come off before the manifold can come off smoothly. This may be corroded and require some convincing.

2) Make sure the manifold comes off the studs vertically and clears them. The injectors are right at the base of the manifold. It would be easy to damage one if the manifold were to drop down in the wrong orientation on the studs.

2) When replacing the valley pan, have a new set of bolts ready (12). The old ones were corroded, and new ones are less than $1 each.

3) The thin pipe marked with the blue dashes carries coolant to the thermostat housing. It's held in place by the bolts that secure the valley pan. This pipe has to be moved from the housing when replacing the valley pan. Replace the 0-ring that seals the front of the pipe before re-assembly. This o-ring comes with the AllGermanAuto expanded kit.

4) When ordering your parts, consider adding an extra coolant drain plug to your order. They're blue, plastic, and incredibly brittle when they get old. It'll cost you ~ $5.