4.8l Water Pump and Coolant Transfer Pipe

[jfoj]

So I have a 2008 4.8i X5 with 77k miles on the odometer. I purchased the vehicle in February of this year with 66k miles on the odometer and decided because I have a lot of road trips coming up, this would become my main road warrior.

So far so good, still have a few things to PM on the vehicle, but it was in very good shape when I purchased it.

I replaced the fuel pump before my first 2300 mile road trip in May. I know all too well about BMW fuel pumps and did not want to chance a failure on a 7-8 year old vehicle. The pump was not as cheap as the E46 pumps I deal with on a regular basis and this pump was a rather big PITA to replaced, not the 15 minute job like on the E46/E39. Glad I did this on my schedule and not the cars schedule.

After monitoring the engine coolant temperature, I decided that these engines run way too hot, even more so because the engine coolant temperature sensor is not in the output of the cylinder head, but at the thermostat. So in installed a 90C thermostat. So far not MAP thermostat errors and everything seems to be running fine, much more comfortable with the engine coolant temps always below 100C! So far I think I have seen 95C in traffic on a pretty warm day, but things cool off quickly once air is moving over the front of the vehicle.

Things have been going pretty well, I have put 11k mile on in 6 months!

Went to take a 2300 mile road trip a few weeks ago, 2 days before I had to leave, start the engine and I hear a faint knocking that I knew was NOT GOOD. Of course, 2 days before I need to leave and drive 2300 miles in August! Listen to the noise, do not spend much time on it and decide it is either a belt idler pulley (which one of the 3?) or the water pump, but clearly a bearing on the accessory belt.

So I order from my local dealer that is a very large stocking dealer and assume they will have the 4.8l pump in stock, but NO, they have to order the parts. Well I have to leave, no parts, no repair, what do I do?? Do I abandoned driving the X5 or do I chance it? The knock was faint, but I knew it was a problem, just not exactly what the problem was and how long I could survive.

So I said to myself, damn the torpedoes, I could stress out about it, or I could be aware that this could fail on my while traveling and then just deal with the failure. So I sucked it up, knew if the temperature started to climb or I suddenly lost steering and charging, I would be quickly be pulling off to the side of the road.

Well as luck had it, I drove the first 1150 miles of the trip and made it, BUT the noise was no longer a faint knock, it was starting to sound clearly like a bad bearing/coffee grinder, but it seemed to settle down a bit at higher engine RPM. Still a bit nervous, but without parts and 1150 more miles to drive, what do you do. Well I drive straight through 1150 miles with an average speed of 72 MPH and made it home. The good news is the bearing was noisy, but never did the water pump seal start to leak coolant to any degree. After dis-assembly there were some small coolant stains on the inside of the water pump pulley, but these were due to light seepage.

Picked up my parts the following day, then realized the 4.8l has some funny 3 inch pipe without replaceable O-rings that I should get along with replacing the plastic water pump pulley because it is 8 years old and plastic. So I order a few more parts. Then I start thinking, yes this is not good.

The old coolant transfer pipe leak on the N62 V8 engines! So I knew of a few options, but not sure I wanted to tear the upper intake off and get this far into the engine for a PM on the coolant transfer pipe.

After a bit of research, I found a possible coolant transfer pipe solution that I thought I should consider. For $199, the BimmerFix coolant pipe stent looked pretty promising. Only the water pump needed to be removed to install this stent and I had the water pump off the engine. So I ordered the BimmerFix coolant pipe stent and installed this as a PM on my engine.

Not a hard job, a bit tricky with the sanding of the water pump lower casting bump and just had to keep the coolant transfer pipe clean of debris. Overall I am very glad I did this for the piece of mind and hopefully I will never have a coolant transfer pipe leak.

Moral of the story, not sure how long the average N62 water pumps last, but suggest a PM replacement around 75k mile or 8 years and consider the BimmerFix coolant pipe repair stent as well as the 90C thermostat.

Make sure you order the stub pipe that connects to the rear of the water pump and I was actually able to remove the pump and re-install it without removing the crankshaft pulley. Not so easy for those with larger fingers and less patience.

Suggest a new pump from BMW rather than an off brand unit, I did not really look at all the options, but felt a pump from BMW would be a bit better route in the long run.

So I am happy to say that I have the piece of mind that I hopefully will not have a problem with the coolant transfer pipe seal leaking anytime in the near future.

Not sure what kind of time/mileage people are getting out of their water pumps, it would be interesting to hear from others how long their pumps are lasting.

[truckedup]

Hey jfoj, replaced my water pump at about 100k km. Made the same rattle/knocking noise you described coming from the front of the engine. It took about 1000km to go from a faint rattle to a sounds like something is about to blow up. You are spot on saying water pump PM replacement should be around 60k-70k miles.

If our climate wasnt so cold in the winter I think I would consider a lower operating temp thermostat. What brand of thermostat did you put in?

[jfoj]

Thanks for the reply.

After removing the pump I could see the front seal must have leaked slightly and this probably cause the bearing failure and/or the bearing cage broke up.

Luckily the water pump bearing held together for a long time, would have been very bad if it had failed during my trip. I am thinking that the higher, sustainted, RPM may have actually helped things a bit because it probably caused the bearing to be more evenly distributed on the shaft.

But when I came to stop and go traffic, it made me NERVOUS!

I installed a Hamburg Tech thermostat from ECS tuning, but I did not like the Hamburg Tech housing, so I carefully moved the thermostat element from the Hamburg Tech housing to the original OEM housing.

Personally I would like the stat to be be closer to 95C than 90C, this would make me happier. I have been looking at other applications to see if I can find a thermostat element that would fit the N62 housing, but I have yet to find on.

I figured I could always restrict the radiator this Winter if needed with cardboard or swap the original stat back in for the Winter if needed.

But even 90C does not seem too bad so far.

Still was able to average 23 MPG on a 1100 Mile road trip averaging 72 MPH for the entire 1100 miles.