4.8is coolant leak take 2
 

After spending a while replacing the radiator and various gaskets I find myself with yet another coolant leak. I guess now that I fixed the weakest point the next weakest points let go.

It doesn't seem to leak when the car is parked on an incline (nose UP) but does so when the car is on flat ground or parked on an incline (nose DOWN).

It's coming out of the hole in the front of the engine. That's the coolant valley pipe right?

There appear to be 2 ways to fix it.

1: BimmerFix Coolant Pipe Repair. This one is about $250 and looks like it allows you to fix it "in-situ" without removing the intake manifolds etc (looks to be considerably less work).

2: MTC Replacement "Collapsible Coolant Pipe"
https://www.amazon.com/11-14-1-439-9.../dp/B00DFANZNG
This its cheaper at $130 but requires substantially more disassembly of the engine plus I'm sure there will be a lot of gaskets etc that need doing if I take it apart so lots of screwing around ordering extra parts and waiting for them.

Leaning strongly towards option 1 - it looks like it'd save a lot of time.

What other stuff (if any) should I replace when I'm in there? Any gaskets etc?

I have no clue which to go with but since I have gotten older I choose the path of least resistance now fixing stuff. I would gladly pay $120 more if it meant not taking all of that apart.

Just did the Uro pipe kit ($300) which meant changing a lot of things. But it looks like a done deal vs a lesser alternative which causes a flow restriction due to decreased diameter.
Plus once you fix the pipe, you could develop the common valley pan leak.

Might as well get to them both.

After that one there is one other possibility, which requires removal of tranny to replace.

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Hoooold on a minute. So even with the more invasive intake removal + replacing the pipe and seals this thing is likely going to spring a leak again from the back? Can this be fixed preemptively while I have it all apart for fixing the current coolant pipe or is this something different altogether?

You may want to poll for those who had to remove the tranny.

But you're original problem of weep hole leaking is a multifaceted problem which is best cared for with the coolant pipe and valley pan.

Then you can rest at ease everything else with the exception of the pan on back of engine is hoses and o-rings.

Good Luck!

Every time I google “N62 major faults” the list of horror stories is over 10 pages long. It looks like there is a part on the back of the engine with a rubber seal around it that fails. It’s jsut above the bell housing and inaccessible without removing the transmission. So far, my 4.8is has had the following work done:

- valve stem seals
- power steering hoses and reservoir
- coolant reservoir
- alternator
- radiator + hoses
- 4wd plastic gear

- and now the coolant transfer pipe.

I’m going to have to think real hard about whether or not I should keep this thing. I wasn’t really expecting this thing to be as reliable as a Jap but this is just absolutely ridiculous.

I did the Bimmerfix coolant pipe repair and it worked like a charm. No need to worry about that $2 gasket failing again since it is completely bypassed. Replaced the water pump since it had to come off anyway.

You are right about the laundry list of problems with the N62 engine. I also had the alternator bracket gasket fail on me with no warning - just started dumping oil on the ground one morning when I pulled into my local Wawa.


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I ran into issues much like yours in the past year. I thought it was the pipe but after much reading, I found that it was the water pump that was bad. It was leaking out of a small hole on the front of the engine. Anyhow, water pump is much nicer job than the coolant pipe. Good luck.


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How did you work out it was the pump? Any visual indicators? Or did you notice it once you took the pump apart? I'd hate to go through all this work to find out that it wasn't even necessary.

I'm 80% positive my water pump has been done recently since this car has already had some major work (valve steam seals) done already.Not sure why they didn't just do the coolant pipe while they were there... I think the pump has been changed because the colour of the metal on the water pump is different to the rest of the engine that it's bolted to so it's definitely not the original unit that would've come with the engine.

At 130,000 miles the upper radiator hose failed. I replaced it. As soon as that was repaired, the expansion tank went and had a new coolant leak. I replaced it. As soon as that was repaired I developed a leak from the front side of the engine. It grew progressively worse over a week. I had convinced myself that it was the coolant pipe in the valley. Just before tear down, I got under the truck right after idling the engine and the coolant was coming out of a hole in the bottom of the water pump. This is a symptom of a bad water pump. And will worsen quickly.
Now, if the coolant is weeping from a hole in the timing cover, that is going to be the coolant pipe.


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