Need to replace radiator. Should I flush/clean?
 

2006 X5 3.0 Radiator has some small leaks, new Nissens radiator on order.

Should I do a flush while I have the system apart anyway? Or a chemical clean?

What products are most highly recommended?

I have read that some of these products are strong acids that need a neutralizer to be put through after.

Others say not to use the chemical cleaners because you may burn through weak parts with the acid and cause more leaks.

Not sure what the best thing to do in this situation. :dunno:b

Are you doing the coolant pipes? It's the most hard to reach parts of a 3.0 coolant system. Definitely worth replacing both coolant pipes. Everything else can be changed out when leaks occur. Use OEM pipes too. Others are too small. I used calipers to measure OEM vs aftermarket. I have two sets of aftermarket pipes sitting in my garage. They were parts from kits. The transmission oil cooler was a headache. I had to seal it twice. I used OEM seals too.

Distilled water and good flush. Upgrade the water pump to a metal impeller.

My coolant system refresh.

Thanks X5Chemist!
I ordered a kit that has the upper and lower hoses - not sure if that is what is meant by cooling pipes. I read somewhere that there were 'hard' (plastic) pipes that bring coolant into the engine but I think they are under the intake, which I wasn't planning on disturbing (just the radiator, hoses, and expansion tank). I did consider changing the water pump but it's been quiet so I will leave it for now. I didn't even get a new thermostat, I suspect that has been changed already (prior owner did dealership service)

If you replace the tank, replace the holding plate. The plate houses a transmission oil thermostat. The thermostat will likely come apart when pulled out. Plus, two seals for the transmission oil cooler. A low coolant sensor is located at the tank bottom.

I should have posted here before ordering parts!

The kit I ordered from FCP (https://www.fcpeuro.com/products/bmw...17107544668kt1) includes something called the Engine Coolant Reservoir Bracket. Is that the holding plate you are referring to? I didn't order a replacement expansion tank.

Some of the parts are original OEM BMW, the radiator itself is Nissens.

I did also order a replacement coolant level sensor (https://www.fcpeuro.com/products/bmw...r-17137553919a), because (despite my slow leak) the sensor seems to occasionally give false readings.

I did watch a video ahead of time and realize that I'd be unplugging the trans cooler, and that there was a thermostat inside it, but I didn't order a replacement... It looked like a little cylinder that just lives in-line in the cooler hose connection, bathed in oil all the time... I didn't think it would be a problem.

Even though the kit comes with Zerex, I also ordered OEM coolant ( https://www.fcpeuro.com/products/bmw...ze-82141467704 https://www.fcpeuro.com/products/bmw...ze-82141467704)

I don't know what the O-rings shown in the kit go with, can you tell by looking at them?

I just came off another job on this car where I bought new parts and that made things worse, so I was trying to just replace the part I know is bad without trying to swap a bunch of stuff 'just because'. Maybe that is not the correct approach in this case?

It sounds like you recommend changing:
- the trans cooler t-stat
- The seals for the trans cooler (Do you know what PNs the trans cooler seals are? )

You also mentioned
-coolant lines (am I correct in thinking those are hard plastic lines under the intake which I won't necessarily be accessing if I just stick to replacing the radiator?)
-Water pump (eek, I guess I could do this as well)

What about the engine t-stat?

Whatever you do, clean the old parts with water then put them in a box in the trunk.
Never know the brand-new part may fail. Now you have the old spare in the trunk.

I wouldnt chemical flush. I did that on the 4.6 and right as we buttoned everything up, the water pump started leaking.

Not saying all chemical flushes will do that, just sharing a con from experience.

If its always been run with coolant, the system should be clean enough that the drain and fill from replacing the rad should get any crud out.

I second the trans thermostat and trans cooler seals. Have had the thermostat break pulling the expansion tank and had trans cooler seals leak.

"Just because" is often recommended for the cooling systems of these trucks and other BMW's of this era. I experienced why.
I've had hoses leak one after the other and after the first few, did all the remaining hoses in one go.

If you want to do a partial cooling system refresh while you're there, I'd add the 2 auxilliary water pump hoses and the expansion tank (OE only for the tank!).

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

Just wondering if anyone has done this: vinegar + distilled water. Run it for 30 min bc vinegar cleans up mineral deposit well.

Then drain, refill with distilled water. Repeat a few cycles then add distilled water + coolant for the final fill?

+1 the trans stat will almost certainly fall apart when you pull it out, look very carefully for the locating tab when you install the new one. Nissens is really good so no problem with that for the radiator. The new coolant sensor usually comes with the expansion tank.

As far as the cooling system flush, back in the day it was usually some combination of corrosion, and silicate in the antifreeze to protect against the corrosion that caused the buildup that needed to be flushed out. These days when the (bmw recommended) antifreeze is silicate free and still protects everything and everything is aluminum I think way less of a problem, unless maybe someone used the wrong antifreeze or added something that shouldn't be in there.