2006 BMW 540i, N62 coolant leak

[Chrisblob 3]

Hi all, my 2006 540i with the N62B40TU V8 has sprung a coolant leak. I'm needing to top-up around 1L of a 50:50 BMW blue/DI water mix weekly. I got a repair shop to take a quick look under the car to see where it leaks out (it spills off near the rear of the drip tray when I turn or drive up/down an incline), but they said they couldn't really see other than it was from somewhere near the rear of the block where the transmission bolts on. I've bought a cheap borescope, removed the engine cover, air filter and throttle body, then had a poke around with the borescope around the front part of the top of the valley pan - found a potential leak in a Y splitter on one of the coolant lines leading out of the reservoir, behind where the throttle body valve sits, image below. There was some coolant on the top of the valley pan near and around the area beneath that Y fitting, but not a huge amount, nor could I see how what coolant had ponded there would eventually make its way to and drain out at the back of the engine. Has anyone else with an N62 V8 struck a leak with that Y fitting? I read they're a bit prone to premature failure. If that was the fitting that failed for you, was the coolant falling out at the back of the block for you also? I guess there is no harm replacing the leaking crappy plastic part with a bronze one as other N62 folks have done, but I'm not convinced that is the primary source of the coolant I'm losing.

Cheers, Chris W, Chch

[Eagle 1514]

You really need to have the cooling system pressure tested to see exactly where it's coming from

[Chrisblob 3]

46 minutes ago, Eagle said:

You really need to have the cooling system pressure tested to see exactly where it's coming from

The workshop who checked it for me (while they were also doing it's WOF) did pressure test, and confirmed it was leaking, but said that they'd need to spend time (and more money) pulling bits off the underside to find where the coolant was coming from. They're not BMW specialists, and while they did fix a significant oil leak for me a year ago (for much less $$$ than I expected), I get the feeling they're not enthusiastic about costing me money just to diagnose the leak location. Unfortunately I cant get under the car in my single garage at home as I don't have any jacks or ramps, so removing the drip tray and getting in under there myself to see things up close is not an option. I'll talk to some BMW/European specialists about getting a diagnosis, but will do my best to diagnose it myself to save any money I can on what I fear will become an expensive repair. If it's the dreaded coolant transfer pipe I'll definitely force the repairer to use the AGA expandable pipe, but first things first - find the source of the leak.

Cheers,

Chris W, Chch

[Eagle 1514]

Yeah hard to diagnose these things without tools and ability to get car in air. Did they take the tray off?

[Spinner99 53]

I have a 2007 N62B48 and had a coolant leak that I first spotted as a trail of water coming out about 1 foot behind the drivers side front wheel (first photo attached).  When looking up from under the car the coolant was coming down the exhaust and dripping to the floor from there.  I was was looking for a coolant hose around the bank of the engine leaking but I couldn't find the source at the back of the engine and eventually took the intake manifold off to get a better look.  I felt quite silly when I found it was the Y connector way up the front of the engine that was leaking.  I replaced it with a brass one from supercheap.   Here's some pictures in case they help

1.  The first sign of the leak,  coming out behind the drivers side front wheel.

2.  A photo with the Intake Manifold off,  there's coolant everywhere, but I put some arrows  in the photo to show where and which direction it was going to get out the back of the engine.  The leak was filling up the channels either side of the valley (but mainly the Cylinder 1-4 side) and was overflowing down the back onto the exhaust.  

3.  The photo is a bit dark but hopefully you can see I just wiggled the hose and the y connector snapped clean off leaving part of itself inside the small hose attached to the Cylinder 1-4 bank.

If you have the throttle body off you should be able to replace the Y connector from there, there's no need to take the intake manifold off if you don't want to.  I thought I was looking for something up the back of the engine and wasn't having much luck with an inspection camera so was trying to get more visibility by removing it.  It never occurred to me the leak could be way up the front of the engine when it was coming out way down the back.

Worst case scenario it can't hurt to replace the Y connector you've eliminated that as a future problem.  The plastic was super brittle so it's just a matter of time.

 

 

[Spinner99 53]

Just adding a bonus photo for you of the Y connector I took out (it literally came out in pieces) sitting next to a new one that's in one piece

 

[Chrisblob 3]

On 8/8/2022 at 7:48 PM, Spinner99 said:

I have a 2007 N62B48 and had a coolant leak that I first spotted as a trail of water coming out about 1 foot behind the drivers side front wheel (first photo attached).  When looking up from under the car the coolant was coming down the exhaust and dripping to the floor from there.  I was was looking for a coolant hose around the bank of the engine leaking but I couldn't find the source at the back of the engine and eventually took the intake manifold off to get a better look.  I felt quite silly when I found it was the Y connector way up the front of the engine that was leaking.  I replaced it with a brass one from supercheap.   Here's some pictures in case they help

1.  The first sign of the leak,  coming out behind the drivers side front wheel.

2.  A photo with the Intake Manifold off,  there's coolant everywhere, but I put some arrows  in the photo to show where and which direction it was going to get out the back of the engine.  The leak was filling up the channels either side of the valley (but mainly the Cylinder 1-4 side) and was overflowing down the back onto the exhaust.  

3.  The photo is a bit dark but hopefully you can see I just wiggled the hose and the y connector snapped clean off leaving part of itself inside the small hose attached to the Cylinder 1-4 bank.

If you have the throttle body off you should be able to replace the Y connector from there, there's no need to take the intake manifold off if you don't want to.  I thought I was looking for something up the back of the engine and wasn't having much luck with an inspection camera so was trying to get more visibility by removing it.  It never occurred to me the leak could be way up the front of the engine when it was coming out way down the back.

Worst case scenario it can't hurt to replace the Y connector you've eliminated that as a future problem.  The plastic was super brittle so it's just a matter of time.

Cheers for all that, I've not taken the intake manifold off but with the borecam I've now followed the route you've outlined in red arrows and can confirm there is coolant all the way along the channels along bank 1-4 right to the back of the engine where it drips down. I'll find a replacement Y fitting, hopefully a brass one, and see how it goes.

Cheers,

Chris W, Chch.

[Chrisblob 3]

Success! I removed the Y fitting yesterday, and it was munted - the connectors on 2 of the 3 ports of the fitting were mush and disintegrated when I tried to remove the hoses from them, and bits of those 2 broken ends I couldn't remove from the hoses, so I replaced the 2 hoses that run from bank 1-4 to the fitting and from bank 5-8 to the fitting, with suitable grade coolant hose - I replaced all the crimp hose clamps with screw hose clamps. The only thing I'm not 100% certain about is the fitting I used - the SCA branch I went to didn't have Y fittings, only T fittings, and in brass ones they didn't have the correct size, so I ended up with a plastic T fitting. I'll source a correct size brass Y fitting from somewhere, but for now the car hasn't leaked a drop after 24 hours and 100km of driving so I'll take the win for now but ensure I replace the plastic T with a more hardy and better for reducing flow turbulence brass Y 😃

[Spinner99 53]

Nice, good to hear it's all sorted!  Was it possible for you to do everything with the Intake Manifold still in place or did you need to remove it in the end?

[Chrisblob 3]

14 hours ago, Spinner99 said:

Nice, good to hear it's all sorted!  Was it possible for you to do everything with the Intake Manifold still in place or did you need to remove it in the end?

Cheers, the intake manifold stayed on. Was a bit tight especially on the passenger side due to the air intake purge valve off the side of the intake, but I unclipped the valve and once that was out of the way it was a bit easier to get a tool around the hose to pry it off - it was a fricking stubborn one but a few choice words and some brute force later and it relented. I will make a point of replacing the replaced hoses before too long with stronger twin ply silicone stuff (I used cheaper rubber single wall for now), and also source a brass Y fitting instead of the plastic T that was available, but the car is running without leaks for now - I wish the E60 had visible oil /coolant/engine temps on the dash or via iDrive to see if the T fitting has made the flow efficiency and hence cooling performance worse, but after more than 100km of running including some spirited bursts out near Chch airport the engine is smelling like it's operating normally and not getting too hot. Fingers crossed it's all good 🤞🙂

[Spinner99 53]

I wouldn't be too worried about the Y (or T) valve inhibiting cooling performance.  Those hoses are fairly small and they return to the expansion tank so my guess is their purpose is to act as an escape/bleed for air trapped at the top of the heads rather than cooling of the engine.

 

[Chrisblob 3]

On 8/15/2022 at 3:00 PM, Spinner99 said:

I wouldn't be too worried about the Y (or T) valve inhibiting cooling performance.  Those hoses are fairly small and they return to the expansion tank so my guess is their purpose is to act as an escape/bleed for air trapped at the top of the heads rather than cooling of the engine.

 

In any case by the time those new bits of hose and the fitting start to degrade and cause further leaks I'll probably have had to deal with some of the other leaks the N62 is famous for. For now however the car is leak free apart from somewhere in the window washer system - I can live with that, because that won't overheat the engine or leave coolant or oil anywhere, just bird kak on the screen 💩