Need to replace radiator. Should I flush/clean?

[Factory6speed]

For the m54, get the aluminum thermostat housing over the plastic one. Also the sensor on the lower radiator hose has a small o-ring that tends to leak very often. Order a few of those o-rings.

The plastic tanks can be a mixed bag, I had to send one back that was leaking, but this one has been good.

You can drain the block out, there's a 13 mm plug on the exhaust side of the block near cylinder two. You can get to it from the top but it's blind, it's a little tricky. Underneath isn't much easier. The small quarter inch ratchet works. If you decide to open it order a replacement plug and washer. Another solid gallon and a half a coolant will come out and it will drip everywhere, either a lot of time with the rag or pressure wash is needed. If you have a big enough drain pan you can get most of it in there. But cover the floor with as much cardboard as you can find before you start, even the radiator is hard to get clean.

I never did a flush on these cars, just a good drain and vacuum fill with distilled water. Drive it for a few days. Drain again. Repeat two or three times until it comes out clear. Then fill with the nice blue before it gets cold outside.

I used to do a flush on the Honda, just put in the garden hose up to the thermostat housing and lett it gush out of the upper hose. You could probably do that, but you still would want to run with water for a few days I think. You would also have to jump the connector for the heater valve to ensure that's opened. But you wouldn't have to drain the block.

[ThreeGermans]

Originally Posted by X5chemist

Transmission oil cooler part number: 171101439140 BMW
Transmission oil thermostat: VEM-V20991274
Water pump: Dayco DP269 with warranty for 125k miles, metal impeller
Engine thermostat: Mahle Behr 11537509227

Thank you!!

FYI The first item (oil cooler seals) has a typo (17101439140)

The Vemo Trans oil t-stat PN you listed and the BMW one are both around $80+ and I'm inclined to buy the BMW one unless you know the Vemo one is better?

[ThreeGermans]

Thanks for pointing out the block drain, I didn't know about it. Looks hard to find.

Do you know who makes the aluminum thermostat housing and their PN? All the ones I found at FCP look like they are plastic.

Do you have a PN for the O-ring seal on the sensor on the lower radiator hose?

Thank you!

Originally Posted by Factory6speed

For the m54, get the aluminum thermostat housing over the plastic one. Also the sensor on the lower radiator hose has a small o-ring that tends to leak very often. Order a few of those o-rings.

The plastic tanks can be a mixed bag, I had to send one back that was leaking, but this one has been good.

You can drain the block out, there's a 13 mm plug on the exhaust side of the block near cylinder two. You can get to it from the top but it's blind, it's a little tricky. Underneath isn't much easier. The small quarter inch ratchet works. If you decide to open it order a replacement plug and washer. Another solid gallon and a half a coolant will come out and it will drip everywhere, either a lot of time with the rag or pressure wash is needed. If you have a big enough drain pan you can get most of it in there. But cover the floor with as much cardboard as you can find before you start, even the radiator is hard to get clean.

I never did a flush on these cars, just a good drain and vacuum fill with distilled water. Drive it for a few days. Drain again. Repeat two or three times until it comes out clear. Then fill with the nice blue before it gets cold outside.

I used to do a flush on the Honda, just put in the garden hose up to the thermostat housing and lett it gush out of the upper hose. You could probably do that, but you still would want to run with water for a few days I think. You would also have to jump the connector for the heater valve to ensure that's opened. But you wouldn't have to drain the block.

[X5chemist]

BMW dealers sell VEM-V20991274.
The thermostat housing has an integrated sensor. It's easy to replace. I didn't find an aluminum housing when searching for an M54. I copied and pasted from an excel spreadsheet. I'll correct the oil thermostat number.

For O-rings, I bought a kit off eBay. I carry O-rings in a bag. Most O-rings can be replaced in a parking lot if needed. Most hoses fail because the metal hose ring fails to seal over time.

[80stech]

You don't need the aluminum thermostat housing. You can put a few wraps of teflon tape around the o-ring on the sensor that goes in the lower hose and it will be good forever. As far as the expansion tank, the OE one was a problem and I don't think BMW improved them, so a good after market one will be as good or better than OE in this case unless someone knows different ? Same with the trans thermostat and coolant sensor, I've never heard anything about the ones that come with a good aftermarket expansion tank give problems ??

I have a thread about the second Standard Automotive tank that I put on my wifes E83 (same tank but thread might be in E83 forum) that was missing the groove for the lower retaining ring. If you look at how that is all put together, the upper hose holds everything together. There needs to be some movement somewhere because the radiator is going to expand at a different rate than the expansion tank and if everything is solid there will a lot of force put on the lower plate. IF there is enough movement in that lower tank connection even with the retaining ring then everything is fine but I don't think there is because people always have trouble pushing that connection together, never checked it myself though. Just saying, interesting

[Factory6speed]

Here is the tstat housing. https://racegerman.com/products/m52t...mostat-housing

13621433077 for the little o-ring. The Teflon tape isn't a bad idea.

[ThreeGermans]

Thank you!
Just in case anyone is reading this in the future, that PN is for the aux fan switch temperature sensor itself, but that gave me enough information to find the O-ring PN, which is: 091158010.

That aluminum t-stat looks cool, comes with the seal and sensor, and is less than half the cost of the BMW part. I was thinking of going for it but I found some conflicting information online.

Originally Posted by Factory6speed

Here is the tstat housing. https://racegerman.com/products/m52t...mostat-housing

13621433077 for the little o-ring. The Teflon tape isn't a bad idea.

[ThreeGermans]

Thank you!

I wasn't planning on replacing the expansion tank (just the "retainer"; part number 17111438819; https://www.fcpeuro.com/products/bmw...x5-17111438819 because it came with the radiator kit).
Should I replace the expansion tank?
What was wrong with the original BMW one and what should I look for in a replacement to make sure the design flaw is addressed?

Are you saying the original BMW trans cooler thermostat is also flawed and should be replaced with something other than BMW (like the Vemo one X5Chemist recommended)?

Originally Posted by 80stech

You don't need the aluminum thermostat housing. You can put a few wraps of teflon tape around the o-ring on the sensor that goes in the lower hose and it will be good forever. As far as the expansion tank, the OE one was a problem and I don't think BMW improved them, so a good after market one will be as good or better than OE in this case unless someone knows different ? Same with the trans thermostat and coolant sensor, I've never heard anything about the ones that come with a good aftermarket expansion tank give problems ??

I have a thread about the second Standard Automotive tank that I put on my wifes E83 (same tank but thread might be in E83 forum) that was missing the groove for the lower retaining ring. If you look at how that is all put together, the upper hose holds everything together. There needs to be some movement somewhere because the radiator is going to expand at a different rate than the expansion tank and if everything is solid there will a lot of force put on the lower plate. IF there is enough movement in that lower tank connection even with the retaining ring then everything is fine but I don't think there is because people always have trouble pushing that connection together, never checked it myself though. Just saying, interesting

[ThreeGermans]

Thank you!

Are you saying the BMW part is flawed and I should avoid it?
I do see the Vemo one on FCP Euro but not from the BMW dealer (at least not the one I'm ordering parts from).

I'd be concerned with Ebay O-rings given you can't be sure of the rubber/composite composition or quality, and dimensions might look close enough but not be quite right.

Originally Posted by X5chemist

BMW dealers sell VEM-V20991274.
The thermostat housing has an integrated sensor. It's easy to replace. I didn't find an aluminum housing when searching for an M54. I copied and pasted from an excel spreadsheet. I'll correct the oil thermostat number.

For O-rings, I bought a kit off eBay. I carry O-rings in a bag. Most O-rings can be replaced in a parking lot if needed. Most hoses fail because the metal hose ring fails to seal over time.

[80stech]

The expansion tank is a huge issue and there is tons of information on that, but yes, it will crack or even explode at some point. AFAIK BMW never made any improvements in the replacement tank but I could be wrong. The OE trans coolers seem to fall apart when you remove them and I don't think the reasonable quality after market ones are any worse than the OE and in some cases maybe better unless maybe somebody knows different ?? Again, just do some searching there are LOTS of threads about those items. As far as thermostats, I think there a couple of brands like Mahle and a few others that have been proven to be good if the OE one is a crazy price, again lots of threads about that.

As far as the o-ring for the sensor in the lower hose I think think the problem there is more that the plastic housing is not perfect and/or ends up distorting a bit so the teflon tape even around the original o-ring might be a better fix than replacing it.