Mercedes-Benz Forum banner

1 - 15 of 15 Posts

·
Registered
2000 S500
Joined
·
15 Posts
Discussion Starter #1
So I posted about 4 months ago and no one was really able to help, so I'll try again and see if anyone has any thoughts. I will start off by saying that all the cooling system components have been replaced. Beginning from a cold start, at idle, the coolant temp is 90C. During low speed driving up to 40-45mph, the coolant temp rises to 99C. If I continue to drive the car, the coolant temp continues to climb to around 114C and will slowly climb from there if I keep driving at that speed. When driving on the highway at speeds 70+mph, the car heats up to around 100C initially, then slowly cools down to around 90C. However, upon returning to 40-45mph, the coolant temp rises again as mentioned above. Once I arrive home after the car has been warmed up, while at idle the coolant temp stays between 96-97C as the fan comes on and off. On the scan tool, the fans are working at 30% speed at the temp. At 105C, the fan controller says its output is 99%. The previous time I posted, I was told to do an exhaust gas test, which I did, and it came back negative. The temperature here is around 55F, so I see no reason for the car to be getting this hot. Any help would be great as i have spent around 4K and still have a car I cannot drive.
 

·
Registered
2005 S600
Joined
·
533 Posts
Did you vacuum bleed the system?

Did you verify that the dash gauge is reading accurately?
 

·
Registered
2000 S500
Joined
·
15 Posts
Discussion Starter #3
I have vacuum-filled the system each time, and the readings I'm giving you are from the scan tool not the dash gauge.
 

·
Registered
Too many to list
Joined
·
8,732 Posts
Have you ever experienced boil over ? The coolant temp sensor may be giving faulty Reading and it may be cooler than it’s indicating .

have you changed the radiator ? They become inefficient with age
 

·
Registered
2005 S600
Joined
·
533 Posts
I see three possibilities:

1. bad gauge reading

2. blocked (internally) radiator

3. water pump impeller bad (no circulation)

You say “all cooling system components replaced”, so, did you do the water pump? The radiator? And with what brand parts?
 

·
Registered
2000 S500
Joined
·
15 Posts
Discussion Starter #6
New Nissens Radiator
New Coolant Temp Sensor
Meyle Water Pump
BorgWarner Thermostat
Víctor Reinz Head Gasket Set( Did this anyway even though I never had the fluid change color , had the heads milled at machine shop)
Mercedes Duo Valve (New Unit)
Rein Upper and Lower Hoses
 

·
Registered
2000 S430, 2003 S430, 2000 S500, 2003 S600 TT, and 2005 E320 CDI
Joined
·
4,558 Posts
Wife's 2000 S500 was having similar symptoms as to yours. Fixed in 2018.

Nissens, they're said to be good. They're made in Slovakia, I think. Got a Nissens fan assembly on the wife's car, and it seems to be doing a fine job. Hers is an early 2000 S500, with the belt drive and the electrical plug in a different spot from later cars.

Meyle, forget them, they're "Chinesium" junk. I know that from experience. Go with either Genuine-MB themselves (it's not that expensive at MBOemParts), or Graf, which is also good; it's made in Italy. I have a Graf unit on the wife's 2000 S500, and that's actually what solved my overheating problem.


Victor Reinz valve cover gasket set, that's also made in China. Better to go with either Genuine-MB or Elring (Elring is the actual OEM for MB).

Rein hoses, that's good stuff, generally made in Germany.

What's the brand of the coolant temp sensor?
 

·
Registered
2000 S500
Joined
·
15 Posts
Discussion Starter #8
I had an oem water pump originally, but I had the issue still so I replaced it again. This would be the third water pump on the car.... So I don't think that's the issue. When I removed both old water pumps, the impellers were intact and had no play on the water pump shaft. This last time I replaced it again out of sheer frustration,
Code:
also I do not know the brand of the temp sensor, but again, I had an oem sensor on there and both have given me the same temperature readings over the same driving conditions. Everything that I listed above has been replaced more than once with the exception of the head gasket. I've also cleaned my condenser while I had the radiator out, and I can see through it, still no change. This entire time it's had genuine MB coolant in the system.
Also i read through your post and your issue was different than mine, at idle my car doesn't overheat, it also doesn't overheat on the interstate, only in town driving
 

·
Registered
2005 S600
Joined
·
533 Posts
Then I think we’re down to the fan.
Because if it stays cool on the highway, but overheats in town, then it’s usually the fan...
 

·
Registered
Too many to list
Joined
·
8,732 Posts
It may be running but not running properly. Have you done the newspaper test where you carefully put a rolled up newspaper into the fan blades to see if it stops the fan , or if the fan shreds the paper ? It may be a running but weak fan
 

·
Registered
2005 S600
Joined
·
533 Posts
So, in addition to the cooling system parts, the heads were removed?

And new gaskets installed?

who did the work?

was the engine overheating prior to the head work?
 

·
Registered
2000 S500
Joined
·
15 Posts
Discussion Starter #14 (Edited)
I did the work, and yes I had the same issues prior to replacing the head gaskets. While I had the heads removed, I had them milled, they took off .006" and .008". And they were pressure tested for cracks and passed with no cracks in either head, nor any leakage past any valve seats. When putting everything back together, I had new head bolts,new cam sprocket bolts, new rocker arm assembly bolts, and new head gaskets. Yes, everything was torqued to spec with an electronic torque wrench, not the cheapo 70$ from sears.

Earlier you mentioned perhaps the temperature reading was inaccurate so I went and took various temp readings. I had my probe on the housing of the coolant temp sensor, as close as possible to the element that gets heated, and consistently was reading about 6-10 degrees Celsius lower than what the ECU read from the sensor. At the hot side of the radiator I measured in between the fins located closest to the inlet for the upper radiator hose, and my temp readings matched what the temp sensor reading was on the scan tool. At the cold side of the radiator, I measured nearest the lower hose in between the fins and had temp readings 20C cooler than the hot side. Granted I realize these won't be perfect since I can't actually measure the coolant itself at the various points but this is what I found.
 

·
W220 Moderator
Joined
·
6,146 Posts
Meyle Water Pump
3. water pump impeller bad (no circulation)
Meyle, forget them, they're "Chinesium" junk. I know that from experience. Go with either Genuine-MB themselves (it's not that expensive at MBOemParts), or Graf, which is also good; it's made in Italy. I have a Graf unit on the wife's 2000 S500, and that's actually what solved my overheating problem.
/\ /\ /\ This !!

I'd want to look very closely at that Pump ;)

HTH,
 
1 - 15 of 15 Posts
Top