Mercedes Overheating, Poor starts & Mileage R129, W124, W201 Coolant Temperature Sensors, Thermostat
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- Опубліковано 30 вер 2024
- Video shows how to diagnose, test and understand your car's coolant temperature sensors and how your car is kept cool. These sensors (including the thermostat) help keep the engine cool, optimally regulate engine temperature for best performance and fuel economy, and help with cold and warm starts. Video also describes how car's achieve ideal engine operating temperature. Video applicable to most R129 SL, including the 500SL, 300SL, 320) most W124, most w201 and for many other 1980s and 1990s Mercedes-Benz, including those with KE-Jetronic.
Four sensors are discussed in detail:
1. Thermostat (technically not a sensor, but functions on temperature) - coolant flow
2. Coolant temperature sensor (CTS) - ignition and fuel (B8/8 sensor in Benz language),
3. ECT sensor (auxiliary fans) - air conditioning and extreme overheating protection (B10/8),
4. Instrument Cluster engine temperature sensor.
Location of parts shown in the video will vary by model and year of car, but they are there.
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Disclaimer - The content of this video is available for informational and educational purposes only. It is not intended to be a substitute for professional advice. I do my best to provide accurate and complete information, however, I assume no liability for any property or personal damage that may arise from any of the information contained in this video. Due to factors beyond the control of Handy Val, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Handy Val always recommends safe practices.
My engine is quite slow to get up to operating temperature 80-85C so I assume my thermostat is always open. On the summer days it takes 6-7minutes drive to reach 80C and on cold winter days that can be 12-14minute drive. At 3:50 you point out the hose that should be warm fairly quickly after engine is up to temp 85C but if I understand good, if the engine temp is only 75-80C this hose must be stiill cold right?
The hose should be warm even before the thermostat opens, as there is still some coolant that flows through a closed thermostat (I didn’t explain this in the video as it’s only a small flow). It should feel lukewarm and you should be able to keep your hand on the hose without burning your hand. Once the thermostat opens, holding your hand on the hose becomes difficult because as it gets really hot.
To answer your question if the engine temp is 75-80 the hose should be lukewarm.
Overall, given what you shared your thermostat is working well. I hope this helps.
here in iraq some of them they remove this thermostat and some of them put 65 ,75 81 .
Could you tell us what is the normal temperature for Mercedes W140 1992 300 sel
Those cars were originally equipped with 87 Celsius thermostats. It’s common to change the thermostat to a lower one, but I’d be careful not to go too low. 65 or 75 seems low, but I don’t have a lot of your country history. A lower thermostat will take longer for the car to reach operating temperature which would be sub-optimal.
you gave the question that i’m searching 6 months!! God bless u! Thank you from Georgia!!!✌🏽✌🏽✌🏽 🇬🇪
Thank you. I really appreciate it. I’m happy the video helped. I have a few other related videos on cooling that you’ll also find helpful. Please watch those too, you’ll like them.
What are the hash marks on the speedo? i.e. I, II, III, IIII? Also, what are the hash marks between 50 & 60 kph? My SL is 2000 and I don’t have any hash marks.
Good catch. Older Mercedes had such lines and in newer Mercedes those lines were dropped. The four different lines represent the maximum speed in those gears. It doesn't seem intuitive, as the km/h seem too high, but it's true. On my R129, it being a Canadian model, the first two yellow lines seem to closely align with the maximum speed limits (60 km/h for major roadway, and in 1992, 100km/h for highways), so many confuse it to relate to speed limits. The hash mark area is certainly meant to cover speed limits within the major roadways and the 50-60km/h is within the common major roadway maximum around the globe.
Thanks! I had a hunch they were related to max speed in each gear. My 1968 manual transmission VW Beetle had similar hash marks, but that car did not have a tachometer. Thanks again!
Yes of course Val - as you know - my R129 just had all these replaced and MORE😢. BUT all is going well and should have it back next week as I was told yesterday. Take care and blessings to you. Mark🙏
Exciting to hear that your R129 will be back on the road again, looking and operating better than ever!
@@HandyVal me to Val🤗
Very informative
Thank you. The video is packed with a lot of helpful information. Appreciate the feedback.
I did a lot of research on this topic and this video makes it much easier to understand. Thank you very much for the time spent doing this.
Thanks you. Happy to help and clarify.
Hi Val, thanks for the breakdown. My mercedes c-class w202 1996 c200. Whilst driving the car temperature is normal. When i pull up and put my car in Park and put handbrake on the needle on my gauge goes to red.
What could the issue be? I'm not sure if this model has an instrument cluster sensor. Could it be the coolant
temperature sensor?
Thanks in advance.
This doesn’t feel right. I know on the 202 they moved to a single sensor starting in either 1996 or 1997. But nonetheless, we need to be 100% certain it’s a faulty sensor or poor instrument cluster connection. So let’s be 100% certain the car isn’t overheating. To do this, you can use an infrared thermo gun (~$25 on Amazon) and point it to the thermostat cover. If that temperature is less than 100C then we know it’s not overheating…and we can investigate further from there. Does the car have any other problems - poor cold starts? Or poor warm starts? I’m trying to gauge if it’s just easier for you to replace the coolant temperatures sensor with a new one.
Hi Val, thanks for the reply. It doesn't show any other issues and I took it for a long drive today up to higher speeds and in traffic without it going over 85°c. When I pulled up on my drive and applied the handbrake and Park gear, the needle shot up to red and the aux fans came on. The needle isn't erratic, it just glides ride up to red.
It does have one sensor on the thermostat housing with the others capped off.
No issues with cold or warm starts as of yet.
I use a thermal imaging camera at work and will use it on the thermostat on Saturday when I'm next in. I'm guessing I should do it when the car is warmed up?
I think the blue sensor main function is to activate the radiator fan on the engine side, and when aircon is on it will activate the auxiliary fans.
Hi. Thanks for the comment. The radiator fan, also known as the viscous fan, is not controlled by blue sensor. It is operated by the speed of the car and it automatically speeds up when warm. The aux fans main function is to keep the air conditioning system cool. And under extreme heat, the aux fans are also used to keep the engine cool. I hope this helps.
@@HandyVal I was thinking about the electromagnetic clutch for the cars that have that type of engine fan. If it's the viscous then it is as you say.
Xlnt info Val!
Thank you! There's a lot of information in the video that is good to know and very important to know, especially if you encounter those symptoms, like overheating, etc.