35d worsening gas mileage - solved- thermostat/fan/EGR cooler - DIY with pics

[POBEP]

first and foremost - big thanks to the community for the extremely valuable knowledge base.
For being a C- home mechanic with the experience of repairing Lada's in late 90’s, this has been on the edge of my comfort zone.

Detailed report.

Cross bar removal
Watch out for small electrical connector attached on the passenger side.
I broke mine - mounting clips separated with very light force.

Black charge air pipe mounting bracket fell down during disassembly.
You can reach it from the power steering / coolant reservoirs side.

Fan removal was super easy. On vehicles with Adaptive Drive there is somewhat less space at the bottom (due to additional AD piping). Bottom coolant hose attached to fan in the center cannot be easily removed from bracket. Instead you can unclip its mounting bracket from the radiator. I spent some time on this one, eventually realizing that BMW mechanics never locked hose in its mounting bracket during past repairs.

Coolant Drain.
I am not a big fan of spilling liquids (probably because I do it anyways).
Diagram here https://www.realoem.com/bmw/enUS/sho...diagId=17_0481
I disconnected coolant pipes #13 and #15 (bottom passenger side) - got 7L coolant out.
If you planning to replace TC thermostat, you should also disconnect line #6 and #9 from TC radiator.
Separating lines #10 and #12 will drain auxiliary radiator at bottom driver side (this is not required).

EGR Cooler removal.
Huge thanks to sgrice for the blue masking tape advise and Shaman electrical connectors disassembly tip.
I disconnected vacuum line and electrical connector from the EGR Cooler switch - it allowed me to remove EGR cooler and set it at work bench.
Ironically, for me this was fastest and easiest major step.

Main thermostat removal
In addition to the rigid pipe mounting bolt I had to remove EGR support bracket (which was held by the same bolt).

Transmission cooler thermostat
Have new part ready to be placed. Consider ordering new nuts - mine were rusted.
I disconnected TC thermostat coolant hose #6 - 0.5-1.0L of coolant came out. cleaned thermostat and TC radiator (IMO, this was important).
Then, slowly lifted TC thermostat on the coolant opening side - another 0.5L of coolant came our from TC radiator (since I missed line #9 drain)
Next, I removed TC thermostat - transmission oil start to poor out from the radiator opening (this was scary, minor panic).
I had my new TC thermostat in my other hand, quickly wiped ports and put new one in, bolted.
I hope my transmission oil not contaminated - it does not mix with coolant and oil was pushed out from the opening (not sucked in)

I finally hit a snag - the bottom EGR cooler plastic hose became extremely loose on the engine side. same issue as reported in post #254. At first, I thought the retaining clip came out and fell somewhere behind one of the pulleys. After some panic time, I realized that clip was still where it suppose to be. I was able to disconnect the hose from the engine - it required light, mirror, curly pick and lots of cursing. Closeup hose inspection revealed that its built-in gasket failed.

I’ll resume in a few days when replacement EGR Cooler hoses arrive.

[captpilly]

Was able to get the boost pipe back on the following day - push up with right hand while pulling down with left hand. You will hear it click in.... total pain in the arse...

Temp is running solid 88-91 now - back in action.

[bfeng]

I haven't had time to do this on mine (73k miles). I tried a kludge for a 200 mile trip I took on Saturday where the ambient temps were around 15-20 degrees. I put thin cardboard over the radiator, leaving the center mounted ATF cooler exposed (and about 3" of the main radiator exposed). Even with this much blocked off temps never went over 74, which is 2-3 degrees above the without-cardboard situation. The efficiency of the cooling system is pretty impressive, eh? Anyway I remove the blockage and I just need to find a free Saturday to do the real fix. Just need some decent weather.

[daytonatrbo]

I have my parts on order to do mine. Coolant temps dipping as low as 65°C while driving in mild weather on the interstate.


Does someone have the torque spec for the aluminum water pump bolts????

[Dieseldonkey]

After change
My mpg up from 21.5 to 24.2!
This will pay for itself

[daytonatrbo]

Originally Posted by Dieseldonkey

After change
My mpg up from 21.5 to 24.2!
This will pay for itself

Where did you get your torque values for the water pump bolts? I don't see them in the OP and I don't have a working gt1 at the moment.

[daytonatrbo]

Originally Posted by Dieseldonkey

After change
My mpg up from 21.5 to 24.2!
This will pay for itself

Mine (preliminary) went from 18.6 to 25!!

[Stockx5]

Mine would not rise above 68c
Few distinctions that might be of interest:

1. Instead of the OEM I bought Beck/Arnley 143-0904 Thermostat Housing. from ebay member 3wardist for $44.67. housing is identical except for the serials and bmw logo. the internals are not the same. you can see oem on the left here and the Arnley on the right.
mainly the Arnley has a bigger copper core, and the springs have a lot less travel than OEM. Which one is a better part not sure but I will be happy to post when it fails.




2. 2 of my t-45 torx nuts on the egr cooler had already been replaced by regular nuts presumably by the dealer. After dropping the non magnetic flange bolts 3 times and finally losing one of them I went to home depot and bought the identical length/thread bolts. this is the size in case someone is wondering.


3.I noticed the EGR valve which had been replaced 18k miles ago by dealer with the updated part was completely caked up in soot. So was the throttle valve and so was the intake manifold.




This is what came of the EGR valve alone


Id be interested to see others egr valves to see if this is normal caking up procedure for diesel engines or if this was caused by the failed thermostat or if this is just what egr cooler does to our egines the car has 103k miles.

Either way it seems a glow plug/injector/EGRvalve/catalitic converter/dpf filter/engine would not last long if this contamination was being constantly pumped in.

[daytonatrbo]

Originally Posted by Stockx5

Mine would not rise above 68c
Few distinctions that might be of interest:

1. Instead of the OEM I bought Beck/Arnley 143-0904 Thermostat Housing. from ebay member 3wardist for $44.67. housing is identical except for the serials and bmw logo. the internals are not the same. you can see oem on the left here and the Arnley on the right.
mainly the Arnley has a bigger copper core, and the springs have a lot less travel than OEM. Which one is a better part not sure but I will be happy to post when it fails.




2. 2 of my t-45 torx nuts on the egr cooler had already been replaced by regular nuts presumably by the dealer. After dropping the non magnetic flange bolts 3 times and finally losing one of them I went to home depot and bought the identical length/thread bolts. this is the size in case someone is wondering.


3.I noticed the EGR valve which had been replaced 18k miles ago by dealer with the updated part was completely caked up in soot. So was the throttle valve and so was the intake manifold.


This is what came of the EGR valve alone

Id be interested to see others egr valves to see if this is normal caking up procedure for diesel engines or if this was caused by the failed thermostat or if this is just what egr cooler does to our egines the car has 103k miles.

Either way it seems a glow plug/injector/EGRvalve/catalitic converter/dpf filter/engine would not last long if this contamination was being constantly pumped in.

One of my EGR cooler flange bolts had been traded for a standard steel bolt. I found the original torx bolt laying in the plastic belly pan. I didn't find it until the job was done. So I have it in my tool box for the next time I have it all apart.


Your soot/cbu looks severe for only 18k miles. But that may be attributable to the cold running engine. The engine is made to run rich when not at temperature, and that makes a lot more soot.

If not for the dpf and catalysts, we would likely have a visual warning that there was an issue because the exhaust would be come darker.


I still can't believe how many of these diesels have failed thermostats and the dealer techs and private specialists still seem unaware of the issue or to check for it.

[CleanIsFast]

I'll be checking my thermostat temps this weekend while the wife is gone. EGR Cooler was already replaced under warranty about 13k miles ago (@41k). Wife drives a lot around town for work and I noticed yesterday her avg mpg was only around 20mpg. I'll reset it this weekend, take a nice drive on the hwy and around town and see what my average is. Compare figures and see if it's just her lead foot or if the t-stat temps aren't getting up to normal operating temperature.

Funny I noticed my mpg in the E39 M5 drop to around 15, and thermostat is replacement is in order (81k miles on original).