[335dsleeper]

A few weeks ago I installed an external wastegate. The gate uses the EGR coolers flange on the exhaust manifold. I opted to connect the EGR coolant hose together as the cooler is no longer installed. Over the last few days I've been watching coolant temps and they're 173-178* while driving and will creep up to 183-185* if left idling for a while. I feel the temps are low. I've read the operating temp should be 88-92c (190-197*f)

So, it's obviously running cooler than it should. I also read that the EGR thermostat allows coolant to bypass the main t-stat. Since I don't have a cooler any longer, I wonder if connecting the hoses together is essentially bypassing the main t-stat and causing the lower temp. Or maybe the main t-stat is bad or maybe a combination of both.

Should I just plug the EGR lines as tdiwyse did with his?

[ice rckt]

How is this external gate plumbed? Has its own dump under the engine splash pan?

[BB_cuda]

Sleeper, I also have no cooler and running a bypass. First of all, our cooler doesn't have a T/S. I was running down at 77C (171F). I changed the thermostat and now run 85-86C. We are a little cooler due to no heat added in from EGR cooler but only a small decrease. If I let car sit in garage idling, it might hit 87C but that's about it. Go get a new T/S and you will be fine. Whether running my bypass or TDI's plugs, we are not seeing a huge difference. I just wanted to go with something I knew wouldn't leak but it's way overbuilt.

[335dsleeper]

Originally Posted by BB_cuda

Sleeper, I also have no cooler and running a bypass. First of all, our cooler doesn't have a T/S. I was running down at 77C (171F). I changed the thermostat and now run 85-86C. We are a little cooler due to no heat added in from EGR cooler but only a small decrease. If I let car sit in garage idling, it might hit 87C but that's about it. Go get a new T/S and you will be fine. Whether running my bypass or TDI's plugs, we are not seeing a huge difference. I just wanted to go with something I knew wouldn't leak but it's way overbuilt.

Ah, our cooler doesn't have a t-stat. I wasn't sure. I never really looked at it. Just removed and put it on the floor next to the dpf and def tank.

I'll swap the T-stat and recheck!

Thanks

[335dsleeper]

Originally Posted by ice rckt

How is this external gate plumbed? Has its own dump under the engine splash pan?

Yes, there's a dump for now. Will re-route to the exhaust as soon as everything's installed and fine tuned.

[TDIwyse]

Originally Posted by 335dsleeper

A few weeks ago I installed an external wastegate. The gate uses the EGR coolers flange on the exhaust manifold. I opted to connect the EGR coolant hose together as the cooler is no longer installed. Over the last few days I've been watching coolant temps and they're 173-178* while driving and will creep up to 183-185* if left idling for a while. I feel the temps are low. I've read the operating temp should be 88-92c (190-197*f)

So, it's obviously running cooler than it should. I also read that the EGR thermostat allows coolant to bypass the main t-stat. Since I don't have a cooler any longer, I wonder if connecting the hoses together is essentially bypassing the main t-stat and causing the lower temp. Or maybe the main t-stat is bad or maybe a combination of both.

Should I just plug the EGR lines as tdiwyse did with his?

Hey. After running a bypass and then finally plugging that line, I didn't see any difference in coolant temps. My thermostat is likely a little weak and I tend to run cooler coolant temps like you're seeing. My 04 Dodge Cummins (no EGR from the factory) is similar in this respect. If I don't load either engine, they're efficient enough that there's not much waste heat to keep the coolant temps "hot". Especially in the 335d after all the deletes...

Here's some good info on coolant temps and engine performance/efficiency for a direct injected diesel.

http://people.bath.ac.uk/enscjb/ch4.pdf

"Figure 4.12 shows the variation of BSFC with water temperature. One of the key advantages of the Diesel engine is apparent in this illustration. It can be seen that BSFC is relatively insensitive to water temperature except at very low power outputs. This is due to the nature of the fuel preparation mechanism and the minimal heat losses in a DI engine. The equivalent data for an SI petrol engine would show a more marked drop in fuel economy at low temperatures. It can also be seen that the major part of the operating map is relatively flat, showing the more uniform characteristics of the engine when compared to an SI engine. The relative insensitivity to coolant temperature and flat characteristic of the DI Diesel are important factors in achieving good all round performance as discussed by Charbonnier (1993). "

I've tracked every fill up from day 1, and after deleting the EGR cooler I noticed much longer warm up periods and lower coolant temps, but no decrease in mpg's for my commute (actually a small increase), which is mostly rural highway at ~55-60 mph. Also no reduction in highway mpg's when driving at 70+ mph. Due to the measured data, I haven't been in any hurry to replace my tstat.

[335dsleeper]

^ I'm not sure. I just want to get it operating within manufactures specs. I don't need the DDE targeting a different load/ fuel/ boost table if it's not seeing operating temp. Might be totally fine but, I'm gonna swap it.

[TDIwyse]

Originally Posted by 335dsleeper

^ I'm not sure. I just want to get it operating within manufactures specs. I don't need the DDE targeting a different load/ fuel/ boost table if it's not seeing operating temp. Might be totally fine but, I'm gonna swap it.

Let us know how that works out.

I've read several followup accounts of the new thermostat helping temps initially, but it doesn't seem to take too long before it weakens and coolant temps get a little low again (more of a problem on deleted cars). But the number of people who post followups months later is very low.

[335dsleeper]

Seems like the euro 335d's take a pretty big hit to their mpg when the engine doesn't reach the desired 88-92c. There's a fair amount of failed T-stats in the UK section. Low MPG, which seems to be corrected when replacing the T-stat. Maybe the DDE software has more on an impact on the euro version. Or maybe your tune is set up differently. Not sure.

[kydiesel35]

Originally Posted by 335dsleeper

Seems like the euro 335d's take a pretty big hit to their mpg when the engine doesn't reach the desired 88-92c. There's a fair amount of failed T-stats in the UK section. Low MPG, which seems to be corrected when replacing the T-stat. Maybe the DDE software has more on an impact on the euro version. Or maybe your tune is set up differently. Not sure.

Interesting. Mine runs at the same temps you stated as well.

[Dazza335iC]

Even my brand-new thermo runs at 84-86C, so OP your temps really aren't off. And as TDIwyse pointed out, diesels aren't very sensitive to small changes in engine temps. Changing it out won't make any difference except lightening your wallet by $50 or so.

[335dsleeper]

Originally Posted by Dazza335iC

Even my brand-new thermo runs at 84-86C, so OP your temps really aren't off. And as TDIwyse pointed out, diesels aren't very sensitive to small changes in engine temps. Changing it out won't make any difference except lightening your wallet by $50 or so.

I'm not concerned with MPG. I want to ensure the DDE is receiving the correct input.

[Dazza335iC]

I didn't say anything about MPG...

Your temps are well within operating specs, and the DDE has broad deadband zones around the operating temp in which it will operate exactly the same. The only time these engines will creep up to the low 90s is when going through a DPF regen. Again, your temps are fine. But feel free to change it if you want, just don't expect the car to behave any differently, because it won't.

[335dsleeper]

Originally Posted by Dazza335iC

I didn't say anything about MPG...

Your temps are well within operating specs, and the DDE has broad deadband zones around the operating temp in which it will operate exactly the same. The only time these engines will creep up to the low 90s is when going through a DPF regen. Again, your temps are fine. But feel free to change it if you want, just don't expect the car to behave any differently, because it won't.

Where are you getting the operating specs? Can you explain the deadband zone you're referring too? Can you post a pic of the coolant table?

[BB_cuda]

I saw 91C when I had my original T/S and no DPF on board. I was stuck in traffic jam in Baton Rouge (September 2015) on I-10. I thought I saw steam coming from under the hood. It turned out to be the catch can plumbing leaking oil vapors. That was the only time I ever saw a high temp. I turned A/C on because fan wasn't running and it cooled the temp down to mid 80s.

I started watching closely after this and routinely saw 77C when running and fully warmed up. After installing new T/S, as I stated above, I run at 85-86C. While bleeding the system of air, I got the radiator fan to self activate which was a relief. Perhaps I had air in the system before T/S switch out. Changing T/S is a lot easier if you aren't running the EGR cooler in the first place. Yet another reason .......

[TDIwyse]

Originally Posted by 335dsleeper

Where are you getting the operating specs? Can you explain the deadband zone you're referring too? Can you post a pic of the coolant table?

As a data point... having taken lots of power data over several winters and summers, I don't measure any power reduction at coolant temps as low as ~170F *. I have no data to compare below that point, as I've arbitrarily chosen that as my "minimum" coolant temp that I will use for doing full power measurements.

*This behavior may be specific to peculiarities of my system configuration and make no claim that it is universal to other modified configurations.

[335dsleeper]

Originally Posted by BB_cuda

I saw 91C when I had my original T/S and no DPF on board. I was stuck in traffic jam in Baton Rouge (September 2015) on I-10. I thought I saw steam coming from under the hood. It turned out to be the catch can plumbing leaking oil vapors. That was the only time I ever saw a high temp. I turned A/C on because fan wasn't running and it cooled the temp down to mid 80s.

I started watching closely after this and routinely saw 77C when running and fully warmed up. After installing new T/S, as I stated above, I run at 85-86C. While bleeding the system of air, I got the radiator fan to self activate which was a relief. Perhaps I had air in the system before T/S switch out. Changing T/S is a lot easier if you aren't running the EGR cooler in the first place. Yet another reason .......

That's a good point. I'm going to try and re-bleed the system to see if it influences temp. I've had the thermostat bolts lose when I was fabbing up the wastegate, it's pretty easy to get to.

[BB_cuda]

my bleed procedure requires only time and perhaps a beer to sip upon. Start car with reservoir cap off and let run for 30 minutes. A fine stream of coolant "pees" back into the reservoir. I saw gaps in the stream early on. I'm not sure it will help your lower temp thing though. Several here switched T/S and got higher temps. TDI did other cooling system work and insured he didn't have air in his system and has already told you he runs cooler.

My BMW tech friend that works at dealer taught me this method. Castle, he works at Advantage Clear Lake

[335dsleeper]

After speaking with a very knowledgeable person regarding M57 coolant enrichment maps... the OEM DDE programing will adjust Quality of injection based on coolant temp. Tuned, it will not (tuner dependent), with OEM programing, coolant temp effects things.

I just ordered an OEM stat from Husker for $62.00.

[TDIwyse]

Originally Posted by 335dsleeper

After speaking with a very knowledgeable person regarding M57 coolant enrichment maps... the OEM DDE programing will adjust Quality of injection based on coolant temp. Tuned, it will not (tuner dependent), with OEM programing, coolant temp effects things...

You should be able to see this in logs of AFR when comparing boost/MAF flow. Also, you can log fuel injection rate directly to see if fuel is being pulled.

I haven't done that at temps below ~170 F to see where that starts happening. If anyone has logs comparing this it would be interesting to see the fuel affects at various coolant temps.

[335dsleeper]

^ I don't have stock programing.

[335dsleeper]

Originally Posted by Dazza335iC

Even my brand-new thermo runs at 84-86C, so OP your temps really aren't off. And as TDIwyse pointed out, diesels aren't very sensitive to small changes in engine temps. Changing it out won't make any difference except lightening your wallet by $50 or so.

Oem thermostat is an 88c as I confirmed yesterday when I pulled my original BMW stat. 88c stamped on the stat.