Now that the weather is getting colder here, I keep getting the P0128 CEL. Scantool doesn't tell what the error is, but it seems to be regarding the coolant not getting up to temp. Since I installed the bigger HE, pump, modified t-stat, couple bottles of water wetter, and about a 80/20 water/antifreeze mix, my temps have been amazing! Not so good for the cold however. I'm not worried about freezing temps and the need to run more antifreeze and don't really want to have to put the stock t-stat back in for the winter months if I don't have too.

It seems as though the mfg wants our engines to run around 87c or 90c in very cold weather. I'm running a max of 82c right now on my short (12 mile) drive to work.

Cause for concern or just keep clearing the codes and roll with it?

What T-stat do you have? I have installed PTE 180* T-stat this summer and when October rolled around, I also got P0128 3 times. Cleared it all 3 times and has been fine since even though it is already December. I think that the ECU will adopt up to a certain point. How many times have you cleared the codes? Also, try switching to 50/50 coolant in the winter.

Yep... I had a whole thread on this issue I turned my heater on when the car was cold in teh bay area and it wasnt able to heat up

Oddly, my heater still blows warm air after a couple minutes. I'm using the TVT t-stat, which was the first on the market. PTE didn't have his until some time later. The simple fix would be to put the stock t-stat back in, but if it's not going to damage the engine, I'm fine just clearing the codes. So far it's thrown a cell for that 3 times.
I just did an entire coolant flush less than 5 months ago and don't want to go with 50/50 unless I have too. Since freezing isn't an issue here, I'm planning on leaving it. If I have to do anything, it will be putting the stock t-stat back.

Let er roll. Running too cool is not going to damage anything. If you get it shortly after start, thats because its not allowing the cats to heat up enough. Its an emissions thing with MB. I have the 180 T stat in a box and have not yet installed it, BUT in Chicago in the winter, I really dont need it either. I plan on doing all of my cooling mods this winter for spring "cool running."

There is a concern you should be aware of and this situation could potentially destroy your engine. While your motor is cooler than normal the block and the piston won't have heated up properly and the proper running clearances will not have been reached. The problem is if you make a hard run with a cold motor (and the situation is worse with a supercharger) the piston is going to see a lot of heat all of a sudden and expand very quickly which could cause a ring to stick in the bore for a milli-second. The block or cylinders still being cold and having so mcuh more mass will respond to this large input of heat much more slowly and so the expansion rate will be much slower.

The differnetial in expansion between the piston and the cylinder could cause the problem above. If you do stick a ring for a milli-second you are going to suffer lots of pressure loss in the cylinder during combustion and lose 10 Hp to 50 Hp or worse.

Jeff

if the ecu thinks your car's engine is really cold, won't the ecu throw more fuel to prevent detonation? If you run rich for long periods of time, it'll kill your cats. OEM cats are insanely priced...some thing to keep in mind.

Wouldn't this be true regardless of what thermostat you are using? Like on cold mornings?
I just made a 150 mile trip at 78 MPH average. The ambient temp was 42* F. Once the ECT got to 156* F, it more or less stayed there (156 -160).

All valid points. This morning on the way to work it threw another CEL (same code). Just before I pulled into my parking spot the engine got up to normal operating temps. Tonight I'm going to cut out a couple cardboard pieces and cover the front of the HE some. Hoping this will get me up to temp quicker without having to make any additional changes. Obviously the cardboard will just be a quick temp. fix/test and I'll be monitoring the temps closely in case I block too much air flow.

running a blocker on the rad has been done for decades on diesel engines. just dont block to much. its a qiuck fix and when you need the cooling it goes bye bye!
you dont need to cover the h/e you need to block some of the rad so the engine heats up

LOL Yes, I meant the radiator, not the HE. Good catch.

You looking to sell your PTE T-stat? Shoot me a pm if you want to work something out.

looks like reading these threads can be hazardous!! now i have the same code!
got any spare cardboard?

What t-stat are you running? I was told the PTE t-stat remains closed until the engine gets up to 180F, which should eliminate the code. Then again, with all the super cooling mods, it still may take longer than the car thinks it should take to heat up still throwing the code....

At the risk of being flamed to death I'm going to add to this thread. AMG didn't design these cars to just go get eggs at the store, they were thrashed and abused beyond what anyone on here will do to them. Engines do NEED to get to between 180-200 degrees to work efficiently and it's really a big deal if the oil isn't up to temp. We being Americans often operate from the "more is better" mind set and it is rarely a good thing. If the car is only tracked, then maybe it could use water wetter. Has the car had problems with over heating while driving? If the answer is no, the temp stays stable, then you may be "fixing" something that shouldn't be fixed. Colder intake air is one thing, over cooling an engine is really a bad thing. If it were mine, I would put the stock thermostat and coolant back in and enjoy the car..............it'll probably run better too.

Should be no risk of getting flamed, it's a good post.
I did have serious heat issues running through stop and go traffic in the middle of summer here. With my cooling mods, the car ran like a champ the rest of the summer and I haven't had any issues since...until now when the weather has gotten cooler. It is very hot and humid down here for most of the year and I suspect that within another month or two tops, the ambient temps will be high enough to justify my cooling setup again. I'm also not thrashing the car while the temp is below 180f. Hopefully covering the radiator will patch me up till the weather warms up in a few months (or days around here).
If I was farther north, then without a doubt using two bottles of water wetter (they had a buy one-get one deal and is the only reason I used both lol) and darn near straight water would be "overkill".

i have the pte 180 tstat. never had any issues with my mods as im in the heat belt just like you. now the temps are in the low 40's and its running cool. my temps are running around 70* C and tossed a cel. once i get it to warm up the temps stay around 80 but the cel is on regarless. i reset it and am going to see if the ecu will adapt. this is a weekender car so im not real worried about it. she can stay in the gagrge under her blankie until spring if needed!

Phil,
I will not argue with you as to what the range for the Normal Operating Temperature should be, but logic of "if it's designed by AMG then it must be correct" is wrong. My cams problem comes to mind. The 2002 cams were replaced with a new part number with a message in EPC not to use the old part number. Or all the transmission jerk problems. Or the radiator issues. And the list goes on.
I'm using PTE 180* T-stat myself and got a P0128 code this morning. My ECT this morning for the 30 min. commute was 153* F. So, I don't know what I will do about this myself but I still feel strongly about what I said regarding AMG. I guess what I'm saying is "Trust but Verify".

Yeah, I'm not saying these things can't be improved, MB and AMG have a tight set of guidelines to work within. (Fed emmisions etc.) They have laid a few eggs along the way too, but something as basic as cooling I tend to believe they can do that. I mean if the cooling systems are truely marginal, the thing would have completely overheated the first time they took one out on a track. I'm not saying they're perfect, but a lot of design and engineering goes into these cars. Still, overcooling an engine is a bad thing.

No, it would be called enginekill since it isn't antifreeze and you hope the freeze plugs popped. It was 12 degrees here this morning, I hate this ****. Maybe you could hit some middle ground like stock thermostat and waterwetter. Just a thought.

Touche'.lol I grew up in northern MN and was stationed in Grand Forks, ND for 7 years. I'm all too familiar with the cold and need to "winterize" vehicles. 50s down here is "cold".

+1, exactly, the ML 55 with the new DMV-1 Blizzaks comes put to play now, so I really dont care if the 32 or the 55 come out at all right now!! (plus, I really dont like the salt on the roads!!)

Silver - would it be possible to let the car idle a bit (3-5 mins max should do it, I'd think) to get up to temp before you start your brief commute? Might prevent the CELs, might not - but maybe worth a shot.

Excellent point, and one that you would think would be fairly obvious. I keep the car in a heated/cooled garage and generally let the car idle for 2-3 minutes. My thought was that since the garage was warm, it would take less time to warm the engine. I'll let it idle longer the next cold day we have and see what that does. Can't hurt!

Tonight as I was driving home the ambient temp was 67 degrees. Tomorrow is supposed to get into the mid 70s. Couple days ago we had snow just a few miles north of us. The weather around here is . This is why I don't want to go crazy changing coolant or putting the stock t-stat back in. Coolant temps were 195f on the way home tonight. By contrast, coolant was 175f when I pulled into the office this morning. Crazy.

That sounds odd to me, in moderate outside temperature to have that big of a swing (175-195) almost sounds like there is some other issue. Really, you're just driving to work and once the thermostat opens your temps should be very stable, unless of course you're sitting still in heavy traffic for a long time.