DIY - Replacing lower radiator hose and temp sensor
 

(Replacing lower radiator hose and temp sensor on 2005 3.0i)

I took some pictures while I was doing this work, and thought I should put together this simple DIY for those who prefer to see how it is done before they start on their own.

Working on a cold engine:

- I took off the plastic undercover/dirt shield under the engine. This was as easy as removing ten or so 8mm and 10mm bolts.

- Drain the coolant from the radiator. (open the blue color drain plug on the driver side of the radiator, and open cap so air can get in.)

- Looking down on the passenger side, you can see the electrical connector on top of the temp sensor:

http://i263.photobucket.com/albums/i...nsorbefore.jpg



- remove the electrical connector by pushing in on the metal clip and pulling the connector directly upward

http://i263.photobucket.com/albums/i...nnectoroff.jpg


- remove the temp sensor by pushing in on its side clips and pulling/wiggling it directly upward:

http://i263.photobucket.com/albums/i...psensoroff.jpg

- both ends of the hose have metal clips that help lock it in place. These clips must be pulled off half way to release (using a needle nose pliers or flat screw driver), and then the hose comes off by pulling it directly away from its connection point.

I started with the top part (thermostat side) first. This was no problem and the hose came off easily after the metal clip was released.

http://i263.photobucket.com/albums/i...upper_part.jpg

On the bottom part (radiator side), that was a different story. The hose seemed to have been baked into the radiator... after releasing the metal clip, no amount of pulling/wiggling on it worked. I finally went from the bottom side, and used a couple of screw drivers as levers to pull the damn thing off, all the while worried that I might be damaging the radiator or some other plastic part around it.

http://i263.photobucket.com/albums/i...ottom_part.jpg


Here are the new parts:

http://i263.photobucket.com/albums/i..._001Custom.jpg


I applied a little bit of fresh coolant to the orings inside the hose, and first connected the top part (thermostat side), followed by the bottom part (radiator side).

Pulled the metal clips half way out, then slide the hose all the way in, then push the metal clip back in to lock.

http://i263.photobucket.com/albums/i...thermostat.jpg



With both ends of the hose connected, I applied a bit of coolant to the oring of the new temp sensor and put it in. Then plugged in its electrical connector.


http://i263.photobucket.com/albums/i...mpsensorin.jpg

http://i263.photobucket.com/albums/i...hosebottom.jpg


I tried to reach the engine block's coolant drain plug, but I did not have a long enough extension to reach this plug. For now, I settled for just replacing the coolant that is in the radiator (not optimal, I know), until perhaps the next oil change where I will do a complete flush/refill. Anyhow, since some people in other threads had mentioned they couldn't see/find this plug, here is a picture of it and its location:

http://i263.photobucket.com/albums/i...drainplug2.jpg

http://i263.photobucket.com/albums/i...edrainplug.jpg

To refill the radiator, I used a mixture of 50/50 of BMW coolant and distilled water ($1.xx per gallon). As per instructions found in other threads on this site:

- turn ignition on to 2 (engine not running)
- set inside temperature to MAX (this opens up valves to heater core apparently), start the fan (speed set to low)
- open the bleeding screw located on the upper hose
- start filling with 50/50 solution until no air from bleeding screw
(this spit out and wasted a lot of coolant.)
-close bleeding screw and complete the fill up as needed.
- turn ignition off

- and of course, put the bottom under cover/ shield back on.


I went for a drive and it was all good. No leaks, no overheating. I will check the coolant level tomorrow morning to make sure it is at the right level.

Hope this helps someone out there.

Many thanks to Weasel and youry for various inputs to my questions in these threads ( pointers and fan shroud/leak )

Well done. I have been sitting on the parts for this for months. Thanks for the clear and concise write up. With any luck I can get to this this weekend.

Thanks.

Even though it is a pretty straight forward DIY, I always feel better myself if I have seen some pictures before starting any work. The whole thing including drain and refill should not take more than an hour start to finish.

Faz so you had a coolant leak? I see how did you manage to locate?was it visible without taking the cover off the front of the radiator?I have a mystery leak too , very gradual though half a mug aevery 1000 miles...not located it yet

Good write up. Thanks for sharing your experience

Please see the link that I posted in my top post (this one:http://www.xoutpost.com/bmw-sav-foru...-rad-hose.html) to see how I saw the leak. No need to take any covers off or anything.

If it is a leak through that sensor, it is very little and sometimes hard to see. One way to see it if you drive around until it gets hot, then stop (say for lunch) and when you get back to the car, check that location. You should see some fluid on the bottom side of the hose (right below the sensor). At least that was the scenario in my case.

Thanks faz so I should be able to do a visual inspection of my temp sensor by easily removing the plastic panel under the radiator?excellen post by the way and am hoping it maybe the solution to my mystery coolant loss

Faz have you got a 4.4? mine is a 3.0d so may not be the same..is it part 5 in the pic?

the level sensor?ta

Sorry I edited the top post to specify this is for a 2005 3.0i.

Looking at the realoem diagram for 3.0d, it seems like lower hose is different. (item 3-4-5)

http://www.realoem.com/bmw/diagrams/u/x/111.png

sos
 

i was getting ready to follow your amazing diy. then i ran into this piece as i removed the dirt cover. looking up from the front on the passenger side, i think i located the origin. please tell me anything you can and advise next steps to take. thanks a mil

Thanks very much for this DIY. I was having trouble pulling the coolant temp sensor connector off, as I was pulling on it, rather than pushing, as was pointed out in this DIY.

Tried doing this today. Lower end is also baked on. Took the pan off, pried like all hell, and still couldn't get it off. Having a buddy come by and help later. :(

Try to use the heat gun or hair dryer and heat up the connector to the radiator. This will make the o-ring softer an you should remove it easily. I heated my up to about 200 degree F bottom first then top. I did all my hoses last weekend when doing valley pan, valve covers, CCV, etc. Be patient and carefully with Radiator Connector as you could break it and will cost $$ to replace with radiator.

Cool idea, bt carefully applied brute force won out. Now, however, I think I should have bought a new temp sensor as I might be leaking from there... are BMWs engineered to keep you from re-using old parts that are still working? :P

Now those are going to be a set of dirty nails!

BMW are engineered to keep people from fixing their own cars. Why do you think they have coding for replacement parts?

LOL... ah well at least a new sensor isn't expensive.

A new O-ring should actually do it. You need to know the dimensions for it. The OEM O-ring is green, and will shrink in time. There are aftermarket O-rings (black in color) made out of Viton I believe, and these will NOT leak even after years of use. The "Fanatics" have put together a post with interchangeable parts (you have to search for it - the title I believe has the words "BMW interchangeable parts" in it), and also the "Festers" have this O-ring issue documented, but again you have to search. For this one it's a thread by "Bluebee" I believe and you have to search "coolant sensor" or similar.
No need to buy a new sensor if it's working OK. Just use some 2000 grit sandpaper maybe and clean the brass element from deposits, if any.

- 2004 X3 2.5i with 84K miles...

- Both Upper and Lower Rad Hoses look fine, zero leaks, but I want to be proactive...

- Does anyone have any recommendation of when (years/mileage) to replace the hoses?

- If anyone has had a burst hose: when did it happen?

I think most of the time it is only the sensor o-ring that is leaking. Both of mine where leaking when I bought the vehicles at about 190k. Both vehicles had water pumps and thermostats replaced because they overheated before they where sold to me and neither shop noticed/fixed the leaky coolant sensor!

I've always been told once you see the hoses starting to turn brown from aged rubber it is a good time to replace them - Mine are about 7-8 years old and I may do them again proactively, along with the tank, and maybe the water pump and pulley (will go with EMP Stewart pump and OEM pulley)

If you want replace them proactively, I would say 100k miles would be good time because I do see horror stories on hose bursting on e46fanatics.
Having said that, at 100k, if you don't have previous maintenance records, I would do whole cooling system refresh including water pump, thermostat, expansion tank, hoses.

The 2006 X5 M54 had a partial cooling overhaul in 2015 @ 116K miles.

It is now at 142,500 miles.
The 2 radiator hoses are still fine.
But I may replace them soon.

BMW hose: ~ $85.
Rein Hose (made in Germany) ~ $26.

I replaced upper and lower hoses shortly after I bought the car at around 200k km and at least one of them were Rein and still good many years later at 500k km. That being said the originals didn't look bad either and I actually kept them thinking that if the Rein hose(s) didn't work out I would put them back on!