I'm losing 3/4 cup of coolant (maybe less) each day (60+ miles), and seeing a trail of dried coolant coming from the driver's side, above the trans somewhere. There are splash marks above the starter, so I have a hunch it might be the housing or thermostat or adjacent hoses. Can you help confirm just by looking at the photo? If so, what hoses do I need to purchase? And is the thermostat part of the housing? Thanks so much guys!

 

Thermostat is an integral part of the housing and it's quite common for the housing / gasket to leak. If yours hasn't been changed yet, that's most likely your problem --- I can't determine cause from your photo. While you're changing the housing, it's advisable to also replace the hard pipe between the housing and pump --- it gets brittle and the ends tend to crumble away. Examine the housing hoses closely and replace any that appear defective. Use NewTIS.info for torque specs and procedure.

 

Thanks for your help! Do you have a parts link to the hard pipe in question, mostly so I can see what it looks like?

 

Between the NewTIS site (procedures) and https://www.realoem.com/bmw/enUS/select (illustrated parts lists), there's not much else we need except tools and money.

 

Did you see this post? https://www.northamericanmotoring.co...9-r56-jcw.html Look on top of the transmission first for the pooling of coolant.

 

Thanks all for your advice; the NewTIS is the resource I've been looking for. The fluid seems like is pooling on the transmission housing. And I can definitely hear a hissing in that general area upon engine shutdown.

 

Ok, welcome and glad to help.

 

UPDATE: Replaced the thermostat housing (a technically easy job, but made too complicated by the confined spaces and limited visibility); hoses did not need to be replaced. I bled the system and over 1.5 days had to top it up probably 0.5 cups a couple more times. The coolant level held steady for another 1.5 days... until today. I was backing into the driveway when I saw a long wet trail on the surface I had parked and I went, "Oh crap, what now?" Checked the expansion tank - it was below the minimum level. I'm waiting for the day to warm up a little before I check underneath, but I really hope it's not a leaky water pump now. It's odd (as you can see from the photo above) that the leak was coming from the thermostat area. But what I am saying? This is an R56, so it SHOULDN'T be odd. This could possible get from feeling frustrated (with the thermostat) to pissed off.

 

So I removed the air box/intake and tried to wiggle the water pump return pipe (from thermostat) and couldn't feel or hear any creaking/cracking that might indicate a cracked or broken seal on the WP end; it's not scientific, but I thought I'd give that a try. Checked underneath and it was WET down there, which makes it hard to tell if it's actually the water pump leaking or the seal where the pipe (from thermostat) plugs into the WP. Would really appreciate y'all's input. I have another observation: The expansion tank was pretty much empty from the time I noticed (in my last post) that the coolant was right below the minimum level indicator to the point when I did my latest inspection, which was roughly 1 hour later - do WPs leak that quickly? Or could it be indicative of a crack in the pipe?

TIA!

 

I just went throught this over the past weekend,your water pipe is probably leaking where it inserts into the backside of the waterpump,when you removed the thermostat housing more than likely it cracked around the flange,like mine did ,it seemed ok and did not leak before hand what I gather is it it was only because I disturbed that pipe and seal when replacing that thermostat housing.I did not even pull it out, but it probably had moved sideways causing it to crack and leak,plastic gets brittle from all the heat cycles and the seal gets hard.Here is some advise when installing the new water pipe,use really good plumbers grease not anything else,its tough to pull out the pipe and even harder to put back in especially if you do not remove the intake manifold, it's very easy to remove the intake, when intalling that pipe put it in at a level angle slightly cocked towards the engine block,make sure after its installed that the rubber o ring did not roll on you and get pinched,in my case the first two times it rolled destroying both seals,my sugestion would be as much of a pain in the A!! it is use the old rubber seal and practice inserting the pipe once you get the idea of how it will go in use the new seal and send it home, the first time the seal rolled on me getting pinched on the outside of the pipe and the second time it got pinched on the water pump impeller side,the second time there is no way to tell if the seal gets pinched, untell you fill it up and leaks like mine did. so be cautious seems simple enough but with limited room to work with things break and do not go together as planned ,also be sure not to get the 2 vacuum lines stuffed between to the thermostat houng and waterpipe, make sure all lines cables are out of the way,also make sure you do not disturb andy of the electrical conections, if they are bent over 90 degresse and tight they may cause your car to pop codes.
also one more thing after installing the water pipe into the backside of the waterpump housing, make sure the second step is to install the thermostat housing to the waterpipe and then put the clip on, once the clip is on make sure its in the grove,once confimed then proced with installing the thermostat to head starting with the top bolt but only start the bolt 1/2 way, those bolts are fun!