M103 running warm on freeway, water pump? - Page 4 - PeachParts Mercedes-Benz Forum

MCallahan · #46 06-20-2018, 08:26 AM

If the problem was drag related, ot would tend to get hot at high speed. That's not generally the issue. Drag increases as the square of speed, so slowing down would cool it off. That's not happening.

As for a cooler thermostat, it's not going to change the max temp, just the lower limit. I'll know later this afternoon if the thermostat change has made a significant difference. If not, I'm going to start playing with one of these thermostats to see if I can change this.

tjts1 · #47 06-20-2018, 05:35 PM

Quote:

Originally Posted by MCallahan

If the problem was drag related, ot would tend to get hot at high speed. That's not generally the issue. Drag increases as the square of speed, so slowing down would cool it off. That's not happening.

The OP is driving in 110f. Slowing down isn't going to help with the m103s inadequite cooling system.

ps2cho · #48 06-20-2018, 06:57 PM

Well if the 87C thermostat doesn’t open all the way until 105C then cooling will max out at where the thermostat allows for maximum water pump fluid change through the radiator. That’s my “tag” on theory here...
If the 79C opens 100% at lets say 95C now all of a sudden cooling performance is drastically improved. In lower ambient temps it wouldn’t matter because the engine is able to cool off enough without maximizing the water pumps ability to circulate fluid.

I think soon we can at least eliminate that theory, which is my only going idea right now to help!

MCallahan · #49 06-21-2018, 08:22 AM

Well, so much for that theory... left work and got stopped in construction on the way home (lane rural highway, 60mph to a dead stop for 3 mins). Never moved the needle. Headed to town (70mph rural 4 lane), no problem, even at stop lights. Got into town traffic and there it goes again. Never got much over 110C, but still don't like it.

Two things... it takes at least a 30 minute drive to get it to this point in 95F ambient temps. Also, it seems if it ever gets over the 100C mark, it just never can get caught back up.

Busy this weekend, but when I get some time I'm going to drill some holes in the cap of one of these thermostats and see if it makes a difference. I could live with having a summer and winter thermostat, if needed.

As for full opening temp, all the other vehicles I have ever owned never varied more than a few degrees no matter the ambient. Tells me start to full open temp is probably a range of 5-7C.

MCallahan · #50 06-21-2018, 08:32 AM

Ok, just glancing at some boiling point info... 50/50 coolant mix is good for 106C at no pressure. 15psi cap bumps that up to 125C. I guess technically we are safe at 110C, but I still don't like it. Too many folks saying their car used to hold 85C all the time and doesn't anymore.

tyl604 · #51 06-21-2018, 08:56 AM

Interesting that you say most folks report their cars always held at 85. That's exactly the same for my '81 300SD until recently. For the last couple of weeks it has been settling at about 100 or just a bit over. So I knew something was not normal.

Just replaced my viscous fan and everything seems to be back to normal. The old one was original 37 years old.

ps2cho · #52 06-21-2018, 09:01 AM

Quote:

Originally Posted by MCallahan

Well, so much for that theory... left work and got stopped in construction on the way home (lane rural highway, 60mph to a dead stop for 3 mins). Never moved the needle. Headed to town (70mph rural 4 lane), no problem, even at stop lights. Got into town traffic and there it goes again. Never got much over 110C, but still don't like it.

Two things... it takes at least a 30 minute drive to get it to this point in 95F ambient temps. Also, it seems if it ever gets over the 100C mark, it just never can get caught back up.

Busy this weekend, but when I get some time I'm going to drill some holes in the cap of one of these thermostats and see if it makes a difference. I could live with having a summer and winter thermostat, if needed.

As for full opening temp, all the other vehicles I have ever owned never varied more than a few degrees no matter the ambient. Tells me start to full open temp is probably a range of 5-7C.

Thinking like this? 2/3rds way down
Thermostat Replacement and modification

MCallahan · #53 06-21-2018, 08:18 PM

Yup, exactly what I had in mind.

ps2cho · #54 06-21-2018, 08:53 PM

Accident driving home today...ambient on dash said 114F and was stuck not moving. Was almost at 120C and even with A/C off it wasn't going down so had to dump some heat through heater on max which brought it down to ~105C. I ordered the 79C thermostat and I'll report back soon if that helps at all. This car would run like a dream in anywhere less than 100F LOL! Blows 51F out of the vents in 114F with R134a as long as I'm cruising at 75mph. In under 100F ambient its spitting out 45F.

lorainfurniture · #55 06-21-2018, 09:12 PM

Quote:

Originally Posted by MCallahan

Just a curiosity, what kind of fuel mileage are you guys getting? I'm absolutely dead on 20mpg in the wagon no matter what.

I get 15-20 depending on weather, mostly city driving and my car is a 4matic.

tjts1 · #56 06-21-2018, 11:23 PM

Quote:

Originally Posted by ps2cho

Accident driving home today...ambient on dash said 114F and was stuck not moving. Was almost at 120C and even with A/C off it wasn't going down so had to dump some heat through heater on max which brought it down to ~105C.

Nightmare fuel.

MCallahan · #57 06-22-2018, 08:20 AM

Was curious on the mileage. I actually found a mileage site that graphed out 20mpg as the solid average. Was starting to wonder if maybe clogged catalytic converters were a culprit, but guess not. I have seen a clogged converter cause both poor mileage and slow overheating.

Hit Man X · #58 06-25-2018, 12:14 PM

Does the TE have a front sound panel like my old 89 300E did? The SDL and 300SEL do, I run without them in the summer and run with them in the winter.

ps2cho · #59 06-25-2018, 02:00 PM

Well I installed the 79C thermostat last night. Went to unscrew the bleed port and threads came out! This was a junkyard housing I found a decade ago to replace the plastic one mine came with and I don’t think I’ve ever opened that screw!

Managed to find a slightly larger bolt that I screwed in right enough, but can’t bleed the air out yet. Drive this morning in 90F showed 82C max on freeway, however the drive home tonight should hopefully show improvement - I’ll report back.

ps2cho · #60 06-25-2018, 10:00 PM

Definite improvement. Only peaked just over the image below. This is WITH A/C ON the entire time in 109F. First pic is in traffic around 10-25mph stop and go. Second is back above 65mph. Maybe my old thermostat was tired and no longer was opening, but having it open early definitely seems to give it an advantage in that it gives the engine more time to cool off at speed, and longer to heat up.

When compared to page 1 photos, I am getting the same coolant temp at slow speeds than what I had at highway speeds before. Far more comfortable at this coolant temp now!