[pa944red]

Good afternoon all. I recently purchased a 2011 335d that was deleted by the previous owner. In true used car fashion it developed a coolant shortly after the purchase at the thermostat housing. I am on my second replacement as the first developed a crack and leaked.

Now that it is getting colder in PA I wanted to see how long it was taking to warmup and have found on days below 70 degrees F the car never fully warmups while monitoring the temps on bimmer-tool.

Can anyone with a deleted car chime on what their coolant temps are in colder weather. I have a 35 mile commute over an hours time and in that time the car never makes it to 180 degrees F and can stay as low as 140 degrees F when coasting down hills. I know this sounds like a faulty thermostat but I'm having a hard time with two defective ones in a row. The first was a BMW unit and the second was a duralast unit.

Unfortunately, I did not log the coolant temps with the original thermostat so I have nothing to compare the new readings to.

Thanks for any help and insight!

[lnxguy]

EGR cooler in place or has that been completely deleted as well? EGR cooler has a thermostat as well, if that fails open you'll never get your vehicle up to temp..

If you're seeing 140f (60c) you've definitely got something going on, and that points towards the thermostat (If in fact the EGR cooler is deleted)

Coolant temps deleted or undeleted are the same, only time you'll get them to really skyrocket is if you're doing a regen on a stock car.

[pa944red]

Thank you for the response. I will verify that the cooler has been completely deleted, but I am fairly confident it has been. I just find it hard to believe I bought two defective thermostats. Is there a source that seems to be better than others for replacements or are there brands to steer clear of?

This is my first diesel and with it being deleted I'm not sure what is "normal".

Thank you!

[Master_Chase]

My dads 335d seem to go through thermostats as well. You could but a cover over the grill during the winter as another option.

[pa944red]

EGR cooler is removed. Just completed a 42 mile drive on country roads that is far from flat and the high temp was 158 and low was 134. Outside temps were around 55 the entire trip.

Car has been running in the driveway for 20 minutes and the temp went from 158 to 171. Sure does sound like another thermostat.

Thanks for the responses.

[BB_cuda]

This is one part where buying the OE part is important. I changed one just last week and went from 77C up to 90C coolant temp (170F to 194F). Just change it again.

[Owen81]

Operating temp is 88°C (190°F) and it should hit this fairly quickly. However I have noticed that on a fully deleted vehicle, around -15°C (5°F) it will take much longer to heat up and below -25°C (-13°F) it may only get up to temperature after 45 minutes or so.

If you can, log your coolant and transmission temps. There is a thermostat in the transmission heat exchanger, and if that is stuck open it will be heating your transmission up before the engine hits operating temps.

[Nadir Point]

I drove mine for probably at least a couple years wondering why the heater seemed weak. Didn't need any measurements to notice how much more quickly the cabin warmed up on cold morning commutes.

[avocet]

Originally Posted by pa944red

I know this sounds like a faulty thermostat but I'm having a hard time with two defective ones in a row.

I have had a brand new(Rein, IIRC) T stat work worse than the one I just replaced. That was before EGR delete.

[pa944red]

Screenshot is after driving for 30 minutes with a 15 minute idle warm up in 33° weather. I would say since my transmission temp is higher than my engine oil and coolant it's definitely the thermostat.

The lowest I saw the coolant temp was 94 after coasting down a hill for anyone that is curious.

All I have to say is holy crap the thermal efficiency of this cooling system is next level.

Once I get the thermostat replaced I'll report back with some temperature readings.

Thank you for the input!

[lnxguy]

Get a OE thermostat if there's not one in the vehicle already.

For shits and gigs can you take the coolant temp with an IR gun on one of the coolant hoses? Wondering if maybe the temp sensor itself is bad?

[Captain Buumer]

OEM thermostat is not good either.

My old one (OEM) lasted only 1 year and then it never reached above 77 degrees.
I did change EGR one to see if it was stuck open but did not improve temps.

~6 months ago i changed thermostat again (OEM). It worked fine - reached 88 degrees as expected but yesterday it's again stuck on 80 degrees.

So thermostats suck especially the OEM ones with BMW stamp on it from my experience. I'm actually looking forward to some aftermarket brand that maybe lasts longer than 1 year.

I even tested the OEM bad thermostats with 99 degree water. It fails to open.

So stupid problem. The price increases but quality is to the crap.

[BB_cuda]

Originally Posted by Captain Buumer

OEM thermostat is not good either.

My old one (OEM) lasted only 1 year and then it never reached above 77 degrees.
I did change EGR one to see if it was stuck open but did not improve temps.

~6 months ago i changed thermostat again (OEM). It worked fine - reached 88 degrees as expected but yesterday it's again stuck on 80 degrees.

So thermostats suck especially the OEM ones with BMW stamp on it from my experience. I'm actually looking forward to some aftermarket brand that maybe lasts longer than 1 year.

I even tested the OEM bad thermostats with 99 degree water. It fails to open.

So stupid problem. The price increases but quality is to the crap.

You put thermostat in water on stove and it didn’t open at 99C?

[Nadir Point]

The one I talked about a few posts back is out again now, BTW. Just a quick vehicular seasonal reminder from BMW. Don't know it until the temps start dropping...

[fsd350]

I will be replacing mine after about 9 years and 30k miles. It originally failed at around 52k when I bought the car in 2015. I think I replaced it with an OE BMW back then. Just took it for a drive the other day. It's not my DD. Temps were between 78 and 81c. I l like Mahle parts, It was like 57 bucks. Not sure why, but these thermostats aren't so robust. Never had any issues with the housings or seals though. My wife's X5d has been replaced a couple times as well. I only do OE manufacturers no Chineseium.

[emanmor345]

Deleted and my coolant temp still goes top to 190F-195F. Keep your engine cover to hold in heat. When youre deleted it takes a lot longer to warm up.

[Shorepower]

The m57n2 is slow&bad at getting up to temp, and even worse when deleted. Our scandinavian winter is tuff for them… I’ve have had two 335d’s and serviced maybe 10 cars with m57n2 engine. In my experience, the only tstats that work are the original ones from BMW, period. And only if both main and egr cooler tstat is replaced at the same time. The BMW main tstat is made in Austria if I recall correctly, all aftermarket tstats have identical made in italy writing stamped in the plastic mold. And all useless. They quit keeping the temp up within weeks or months.

But the trans heat exchanger also has a tstat, which is often overlooked. To replace it, you would have to buy the complete exhanger, you cant get the tstat only. My solution has been a vag dsg thermostat, it’s an inline thermostat with barb hose connectors in both ends, mounted in the coolant return hose from exchanger. It opens at 75C which is the same as the original in the exchanger. Bought this as Mahle aftermarket, p/n TH575. I’ve been installing these by deafult every time I replace the other tstats, and it works perfectly. And always left the old tstat and the exhanger untouched so it’s a 5min additional task.

[Shorepower]

Originally Posted by Shorepower

The m57n2 is slow&bad at getting up to temp, and even worse when deleted. Our scandinavian winter is tuff for them… I’ve have had two 335d’s and serviced maybe 10 cars with m57n2 engine. In my experience, the only tstats that work are the original ones from BMW, period. And only if both main and egr cooler tstat is replaced at the same time. The BMW main tstat is made in Austria if I recall correctly, all aftermarket tstats have identical made in italy writing stamped in the plastic mold. And all useless. They quit keeping the temp up within weeks or months.

But the trans heat exchanger also has a tstat, which is often overlooked. To replace it, you would have to buy the complete exhanger, you cant get the tstat only. My solution has been a vag dsg thermostat, it’s an inline thermostat with barb hose connectors in both ends, mounted in the coolant return hose from exchanger. It opens at 75C which is the same as the original in the exchanger. Bought this as Mahle aftermarket, p/n TH575. I’ve been installing these by deafult every time I replace the other tstats, and it works perfectly. And always left the old tstat and the exhanger untouched so it’s a 5min additional task.

In one of the local groups someone disassbled the original and mahle egr thermostat. Not even remotely the same. Mahle oe quality is a joke nowadays.

Credits the op of pictures!