Car runs hotter with new thermostst and water pump? - Page 2 - PeachParts Mercedes-Benz Forum

TheV12pwr · #16 07-03-2005, 05:39 PM

Quote:

Originally Posted by Ali Al-Chalabi

Cooler is not necessarily better. Mercedes designs there cars to run at a certain temperature for a reason. If they wanted the car to run at 80C and cooler, they would have put an 80C or cooler thermostat in the car.

On my car, whenever it starts running at 82C or less, I change the thermostat.

Another mistake!!!

Moneypit SEL · #17 07-03-2005, 07:40 PM

TheV12pwr,

I don't know why you're yelling about mistakes and misinformation. I can assure you that thermostats can and do fail in such a way as to prevent the engine from reaching operating temperature. They can also fail by refusing to open. I've seen both. Apparently, you have not.

TheV12pwr · #18 07-04-2005, 02:06 PM

I didn't mean to sound 'yelling',was refering to the guy who staes that 87C +/- 2C fully opens at 102C and will restrict coolant at any temp.below that.
To me this is missleading info.
The guy who started the treath have no complains with overheating or slowly reaching the operating temp.so faulty termostat is not an issue here(do not know why do you even mention it).
My point being, that engine running at 80-85C is better than 90-95C.
I am not sure that this helps anybody,but it's sertently not bad to read different opinions on same issue.
Pls don't kill me for my believes

Arthur Dalton · #19 07-04-2005, 02:26 PM

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HFM-SFI engine management systems run much better at the higher temp. They are lean burn engines by design and that is why the thermo is 87C at open.
If any engine I know of that runs better at higher temps [ read injector duration times] , it is the HFM 104s...the ECU is mapped for it and lower temps actually decrease perfomance on this system.

ksing44 · #20 12-24-2005, 05:33 AM

The dealer found that my fluid was a bit low when I returned for a follow-up visit. They suspected that there might have been some air trapped in the system after the water pump was replaced, all of the hoses were replaced, and the coolant system was flushed. They simply topped it off and now my car runs at 87C. I prefer having the needle just below the midpoint between 80C and 100C, rather than above midpoint and getting closer to 100C. I just think too much heat can’t be a good thing. Now it is back to the way it was before they “fixed” it. That makes me feel much better.

stephenson · #21 12-27-2005, 09:32 PM

Glad got to the real story ... 95 C sounds high relative to what I have seen in the thousands of threads at this site. Most common numbers are mid 80s at normal highway speeds without fans running.

Anyone ever thought how weird it is to have computers running fuel, ignition, etc at multiple cycles per second, with a slow moving analog device like a thermostat controlling the water temp? Guess it means water temp, within a relative broad range, is satisfactory to the far more capable digital control systems ... does anyone have opinion (:-)) on what result would be if the water temp were regulated tightly? (I suspect imperceptible changes in efficiency - unless, the temp could be elevated and safely maintained much higher)

Thanks!

Bio300TDTdriver · #22 02-09-2006, 01:05 AM

I have a 1987 300TDT. My temp gauge says 60c. It ran at this temp before and after I had a new head installed. It has had 3 new thermostats installed. The fan clutch has also been replaced. I also had a new water pump installed when the head was done. Anyone have any ideas? Could it be a faulty gauge?

Thanks,

Strife · #23 02-09-2006, 03:16 AM

Quote:

Originally Posted by stephenson

Glad got to the real story ... 95 C sounds high relative to what I have seen in the thousands of threads at this site. Most common numbers are mid 80s at normal highway speeds without fans running.

Anyone ever thought how weird it is to have computers running fuel, ignition, etc at multiple cycles per second, with a slow moving analog device like a thermostat controlling the water temp? Guess it means water temp, within a relative broad range, is satisfactory to the far more capable digital control systems ... does anyone have opinion (:-)) on what result would be if the water temp were regulated tightly? (I suspect imperceptible changes in efficiency - unless, the temp could be elevated and safely maintained much higher)

Thanks!

Well, the analog (seems to be a dirty word these days) system has built-in hysteresis (slow to react to change), which is actually a good thing in many cases, including this one. Analog closed-loop systems had been around for years and work well. The thermostat has a relatively predicatable lifetime and (generally) fails in a safe mode - open.

Digital closed-loop systems are actually "analogues" of analog systems!

I suspect that the variations that we see in thermostats is not in the closed and open temperatures, but instead in the "gray" area between completely closed and completely open - and these are caused by manufacturing variations in the thermostat. Maybe the real advantage of digital systems is the elimination of manuracturing variations in systems (of course, a digital temperature sensor has an analog signal and an analog to digital converter, both of which have their own pecularities...)

I like to point out to people that old technology is not necessarily bad. For example, the old-fashioned ignition systems failed in a predictable time frame, mostly from the wear of the points, cap, and rotor. With electronic systems, the switching transistor could last 500 years or it might poop out the next time it is called into action to produce a spark pulse - you don't know, and there is no nondestructive way other than statisically to predict it's failure. People laughed at the FAA for using computers with tubes - same thing. Tubes, once past infant mortality, fail in a predicatable time frame, and can be replaced proactively. Transistors might work for 1000 years, or they might fail at the next switching transition.

86560SEL · #24 02-09-2006, 10:46 PM

My 380SE fluctuates. On cold days (below 45-50*F), it usually runs at 65-75*C, sometimes it may approach 80*C in town, but when I get back on the highway or freeway, it goes back down to about 60-70*C, sometimes less if it is below 40*F outside, which is not that often.

I have only owned the car since December and the warmest day since I have had it was in the lower 70s. That day it went to about 90-92*C in city driving and when I stopped at a market, it was pushing coolant out of the tank- where the cap is. It has only did this once, but there was one day after I had driven it, I was removing the cowl cover to clean it out. The reservoir was making a noise and the tank was filling up, but did not overflow. However, my seal on my reservoir cap is broken. I think this was the cause for this, as well as my fluctuating temperatures. If not, I hate to see what my temperature will go to in the summer in city traffic when temperatures are 85-95*F.

At any rate, I am going to install a new cap and see what happens.

Duke2.6 · #25 02-09-2006, 11:25 PM

Well, I know how a thermostats work, and I agree with Ali.

On M103s, in particular, old thermostats appear to "drift" to a lower opening temperature.

When new mine typically ran at about 90 at speed on the highway in all weather, but now it typically runs about 80 on the highway unless the ambient temperature is over about 70F, and since I only drive it from about November to April, it rarely sees much over 70F ambient.

The lower temp is okay by me as it gives a little more time before it gets up to 100C or more in traffic.

I'll sacrifice the possible slight decrease in fuel efficiency for the longer hose life that 80C will yield. Automotive elastomer life decreases exponentially with higher temperature.

Duke

Ali Al-Chalabi · #26 02-10-2006, 01:04 AM

Quote:

Originally Posted by Bio300TDTdriver

I have a 1987 300TDT. My temp gauge says 60c. It ran at this temp before and after I had a new head installed. It has had 3 new thermostats installed. The fan clutch has also been replaced. I also had a new water pump installed when the head was done. Anyone have any ideas? Could it be a faulty gauge?

Thanks,

Running at 60C after 3 thermostat changes. I would seriously investigate the possibility of a faulty temp gauge. If you have access to an infrared thermometer, you can get a good approximation of whether or not the temp gauge is accurate.

sailor15015 · #27 02-10-2006, 01:20 AM

I would also say replace the temp sender. I went through a horrific ordeal trying to replace the t-stat on my bimmer because I thought it was running too cool. After replacing the t-stat and no change I picked up a new temp sender and it turns out it was running at the right temp the whole time, with the old t-stat.

haasman · #28 02-10-2006, 03:59 AM

Quote:

Originally Posted by sailor15015

I would also say replace the temp sender. I went through a horrific ordeal trying to replace the t-stat on my bimmer because I thought it was running too cool. After replacing the t-stat and no change I picked up a new temp sender and it turns out it was running at the right temp the whole time, with the old t-stat.

Seth is right. On the 91 300e I chased what I thought was a running too cool problem for several months. It turned out to be a faulty temperature sending unit. The car had been running at the proper temperature the entire time, the sending unit reported too cool.

Haasman

Bio300TDTdriver · #29 02-11-2006, 12:17 AM

Quote:

Originally Posted by sailor15015

I would also say replace the temp sender. I went through a horrific ordeal trying to replace the t-stat on my bimmer because I thought it was running too cool. After replacing the t-stat and no change I picked up a new temp sender and it turns out it was running at the right temp the whole time, with the old t-stat.

I forgot to mention I replaced the temp sender as well. I will have it scanned and see what it reads at the site of the sender.

Bio300TDTdriver · #30 03-19-2006, 02:15 PM

After reading Dave's excellent post (thanks Dave) I figured out that Euro Car Service in Seattle had wired my gauge to the EDS sensor. Once I rewired to the correct sensor and installed a new sensor the temperature gauge reads 83-85°C like it should. My temperatue gauge is fine. Now if I can just figure out why I have a 100-110°C Electric fan & AC protect switch (3 prong).

here are 4 total temp sensors on the 1986/87 OM603:

1) Dash gauge temp sensor (one wire) - This is located on the side of the head, below the injectors and intake manifold, behind the injection pump. Not easy to access.

2) Tranny shift softener sensor (one wire) - This is a round sensor above the thermostat housing. It triggers a solenoid that is supposed to soften tranny shifting when coolant temps are below 50°C. (I have this disabled on my cars, it just makes them flare when cold.)

3) EDS (Electronic Diesel System) sensor (one wire) - This is on the water oulet from the head, where the upper radiator hose connects. It tells the EDS computer what the engine temp is. AFAICT this is only used for EGR and ARV (emissions junk) operation.

4) Electric fan & AC protect switch (3 prong) - This is a dual-temp switch, it triggers the electric fans on high speed at 105°C, and will kill the A/C compressor as a safety when temps get abnormally high (115, 120, or 128°C depending on which engine & model you have). The 105/128 switch used on the 124 is expensive so I used the 105/120 switch from the SDL, which is cheaper, and I never liked the 128 rating anyway. Photo below.

5) The glow plug temp sensor is inside the relay on the 86/87 OM603 cars. Models with afterglow use an external sensor that replaces the 1-wire dash temp gauge senor in the head (#1, above) with a 2-wire sensor, one still goes to the dash gauge, but the other wire goes to the afterglow relay. (I upgraded my car to factory afterglow and have this 2-wire setup on my car. Photos of the parts required are at this link.)