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

[Shaman]

Originally Posted by sgrice

3) Just to state the obvious, the water pump is separate from the original thermostat repair (though I would not disagree with replacing the water pump at roughly 100,000 miles as preventative maintenance if you need to do the thermostat anyway).

Thank you, Stephen!
Regarding changing water pump - I had recently broken bolt under one of the pulley, so serpentine belt came off and I had a chance to check water pump for any damage and backlash. And it has very little one. So I think once I will be there - I will replace it.

Igor

[diegoX]

Originally Posted by Shaman

diegoX and sgrice, do I need order water pump gasket separately or it goes with water pump?
I assume you did complete coolant flush, how much coolant do I need to order?
and off-topic question: where are you usually shopping for parts?
thanks!!!

Shaman, I got my parts from the dealership (BMW Roxbury NJ). They were the only dealership in my area giving 25% off on parts. Other AEM parts I get from rockauto.com

[ZetaTre]

I think I was one of the first people around here to replace thermostat in my X5 35d.

I don't have the record with me, but it was about 2 years and some 30K to 40K miles ago.

I've noticed most recently that the temperature is starting to get twitchy again: when I commute to work I do notice that there's a certain downhill section along the freeway where the temepreture gets in the low 80s.

The thermostat is slowly degrading just like the old one and I suspect that coming winter time I'll replace it again.

Given that the ones available new appear to be just as bad as the one that was originally fitted (i.e. doesn't seem like nothing has changed) I'll probably not buy an OEM anymore.

I'm not entirely sure who makes it, but looking at pictures it doesn't seem to be Mahle, Febi/Bilstein or Gates.

Notice how in these 2 the center disk is attached differently.

Here's the BMW OEM from down below:



Here's the Gates:



I'll give Gates a try on my next one see if it's any better. The cross reference part number is TH35488G1

[dalecan]

Given all these faulty thermostat readings, I decided to check mine and of course it was faulty. I had planned on changing this when my work schedule got a bit quieter. Interestingly, I called BMW Seattle today to book my X5 in to get the faulty DeNox reading fixed (hopefully under CA emissions) and to my surprise the lady on the phone said my vehicle had an open recall on a faulty thermostat. Mine is a 2012 X5d. Maybe some of you have the same open recall. I was very relieved to say the least.

[josiahg52]

Sounds like the woes we E39 M5 owners experience. No idea the failure mode except the thermostat seems to rub on the seal and over time the spring can't overcome the drag. Could be the seal doesn't sit right or the thermostat sits crooked. Who knows what the problem is with the X5's thermostat.

Knock on wood, my thermostat at 90k+ miles seems to be functioning well. 84C+ even in cold weather. The only time it's lower is sometimes when it's really cold but I never see it below 80C unless I'm coasting down a long hill and it's cold out. Sometimes it takes a while when it's really cold.

I'm going to start paying closer attention.

I've calculated over 32 mpg in the right conditions, maybe 28 mpg in the real deep winter highway driving.

[vetaldj]

Finally was able to change my thermostat today.

It took me exactly 4.5 hours from start to finish. Not that hard with help of this thread! Great job OP!!!

About that white connector you mentioned (that connects EGR cooler to some other connector) - you pull white thing back and firmly push it down, I used pliers but was able to repeat by hands as well. Tricky connector I must say. You need to do it in two steps.

All other very close to what was described but I did not take off air hose coming from the intercooler to the throttle/EGR valve (big one on driver side with metal springs), I just undid top part and move it to the left so it clear way to take off shroud. Also, I did not take off intake muffler, it looks like you did that to fight with that stubborn connector. I did not find why else you need to take that off.

All the rest as in DIY.

[Tuesday]

I think mine stuck shut for a while.Hit 204*F when I shut it off. I noticed exhaust was really hot.So I hopped back in to see gauge .Ive never seen it past 188-190*F ,usually 184 tops.Went for a ride and shot back up to 197*F then cooled to about 190*F for a few miles.Still higher than usual.I bought a ScanGuard after reading this thread to keep my eye on temps.I don't think it has EGT.Do you think it's the thermostat?

[josiahg52]

Do you mean ScanGauge? It has limited use with the X5d but I'm working with the company to get more commands working like EGT, transmission temperature, oil temperature, etc. and fully compatible firmware. Water temperature works great.

You didn't say what the outside temperature was or what you were doing but I've seen 210F before for brief periods on the hottest days and after hitting traffic or having stopped after a cruising period. Driving around,180-195F is pretty standard for me whether it's winter or summer.

[Tuesday]

Yes scangauge.It was only 80* out with a steady 45mph of the last 5 miles before shutting car off.I restarted car to see the 204* after noticing the hot exhaust tings.It was 15* cooler out and car temp 20* higher than normal.Funny thing is I've tried to get car hot,191* tops and only for a brief second.Thanks for your reply j52

[Tuesday]

The dealer recommend not using my Scangauge.Said a lot of codes tripped at one time.Lots of random codes that's didn't go together.Must have been when car cut out for split second and dash lit up on highway.Said I'd buy a new thermostat because they didn't change it because of no code?He said it isn't just a swap it had to be reprogrammed when swapped?