Specific Query regarding Water Pump DIY on M54 engines

Hi all, I'm planning on replacing my water pump (as well as installing metal pulleys) on Friday before a 2000 mile round trip to Italy on Saturday and I really want to replace them before I leave. Car has done 114,000 miles and WP was last replaced with a metal impeller by an indie garage between 60-70k miles.

The pulleys aren't going to be an issue, and so far I've never done any DIYs that involved any sort of refilling & bleeding of coolant system, but I've done all my reading up on it and feel pretty confident, so don't anticipate any problems there.

HOWEVER I dont wanna remove my splash guard/ undertray as I've only just got it fitted securely with cable ties last week whilst the car was on ramps (dont ask, essentially cause I have M3 rep bumper). And also new coolant was only just put in approx 6 months ago. So to my QUESTION, approx how much coolant is going to spill out when i remove the water pump if i dont drain any coolant from the radiator drain plug? Is it going to be a flood of a few litres or are we talking just a small loss? Either way I'll be topping up and bleeding, but just would like to know how much I'll be expecting and how much coolant to buy as I wanna make sure I have about a bottle of coolant spare to keep in the trunk for the trip.

ps FYI thermostat was done in april as it was failing (slow to close so car ran cooler), both tensioners and belts were done by me a few wks ago, expansion tank looks good, although I've got one to take with me on the trip in case it was to fail, as well as a few other bits and pieces.

you'll lose about two quarts of fluid since it is above the block and most of the radiator, but they only sell anti-freeze by the gallon state side so sounds like you have other options over the pond.

This is stupid to not drain from the bottom before you pull a pump out.
Imagine that coolant flowing all over the pulleys and belts before the water pump cavity. Not to mention the pools you'll get on the top of the shield.
Sticky and slippery is not good here. Stop trying to reinvent the wheel.

Originally Posted by QAfred

you'll lose about two quarts of fluid since it is above the block and most of the radiator, but they only sell anti-freeze by the gallon state side so sounds like you have other options over the pond.

Thanks for that, 2 litres I can about deal with, I'm guessing the fluid will initially come out slowly as water pump is coming out, i can rig a container with a funnel. Here in the UK we get coolant in 1.5 litre bottles.

Originally Posted by GoForthFast

This is stupid to not drain from the bottom before you pull a pump out.
Imagine that coolant flowing all over the pulleys and belts before the water pump cavity. Not to mention the pools you'll get on the top of the shield.
Sticky and slippery is not good here. Stop trying to reinvent the wheel.

In order to remove the pulley, belts will have to come off, and tensioners & pulleys could be easily covered, the same as you ought to cover the alternator any time coolant is likely to spill down. But in my case less of an issue as some pulleys getting replaced, so doesnt have to be a great drama

You can't buy less than a gallon of coolant. Buy one. And a gallon of distilled water. Drain the rad, yank the pump and refill. This isn't rocket science.

Originally Posted by Scott ZHP

You can't buy less than a gallon of coolant. Buy one. And a gallon of distilled water. Drain the rad, yank the pump and refill. This isn't rocket science.

Like I already said, BMW coolant is sold in 1.5 litre (or quart) bottles in the UK, I've bought 3 litres, plus another litre left over from when thermostat was replaced. And like I already said its going to be PITA getting my under tray off & on again properly, and I'm only going to have the friday to do it and various other stuff, including packing for the 2 week trip to italy

Will siphon off as much coolant as i can from Exp Tank prior to water pump removal. Will post back how i get on.

I do wish you good luck and your precautions will give you a better shot.
Come back with tips if you are satisfied with your method.

Originally Posted by GoForthFast

I do wish you good luck and your precautions will give you a better shot.
Come back with tips if you are satisfied with your method.

Thanks, I'm hoping to video & take pics of what i do, as i have an idea to minimise spillage when water pump comes out.

One question about bleeding the system once all done, that I've not seen mentioned in nay DIYs. When i do start bleeding the system to finish off, I know to put the heat on max & low blower setting, BUT do i switch on the AC?

AC is unrelated to what you're doing, so to answer your question, it doesn't matter if it's off or on. It helps to have the front of the car a little raised while bleeding, even just on a slight hill or something.

I have replaced half a dozen E46 water pumps; you do not need to remove the belly pan.
If you are concerned about the mess, just stuff an old towel between the pan and the bottom of the block.

Originally Posted by Scott ZHP

I have replaced half a dozen E46 water pumps; you do not need to remove the belly pan.
If you are concerned about the mess, just stuff an old towel between the pan and the bottom of the block.

Thats a good tip. In the end I took so long to get the power steering pulley off to replace with a URO metal pulley, that I didnt have time to change the water pump as it started raining!

I was going to replace the water pump pulley with a URO metal pulley from pelican parts, but on installing it there was a noticable wobble when i put it on to the old water pump, much less noticeable when i stuck on the old plastic pulley back on. But when i put on the metal URO pulley on to the new OE water pump, to my eye as it looked ok when i rotated it. I shall investigate more thoroughly on returning from my trip

So over 900 miles later in Italy and all is good so far, brought along the OE water pump incase it did happen to fail during the trip.

In general I'd not recommend URO in any way shape or form!
Many bad reviews read along the way as I recall.

Originally Posted by GoForthFast

In general I'd not recommend URO in any way shape or form!
Many bad reviews read along the way as I recall.

+1. Sort of like the part of last resort to me.