R129 500sl Overheating in Traffic

[Miro 0606]

Hello everyone.
I'm new to the club.


I'm having an overheating problem with my car when in traffic the temperature goes up to 115.
So far I replaced the water pump, radiator, thermostat, all three switches, viscous fan, belt, tensioner.
I also done the test for CO2.
There's no coolant loss.
There's also cold start problem, for first 2 min the battery light com on, and you can feel misfire.
After couple of minutes the lights gone off.
I swapped the alternator, all fuses and the OVP relay, Battery.
It made no difference.
Does anyone went through this problem?

 

[rifiki]

Over heating, sediment in radiator/engine?

 

[Charles Morgan]

Which car are you talking about?

 

[Miro 0606]

1990 500sl

 

[Miro 0606]

I replaced the radiator and flushed the engine- there's nothing to indicate there's a blockage- wouldn't the car overheats on the long run if there was a blockage?

 

[brucemillar]

Sounds simple.......BUT.

Replace the rad/header cap. A microscopic leak here will allow pressure to blow past as steam, so you will never see it with the bonnet closed (maybe not even with the bonnet open). It it blows past then you will have no coolant pressure so will rapidly overheat when standing still or climbing hills.

Also check the hose from the header tank, to the radiator and any joints at the radiator and the header tank. Same issue with tiny leaks allowing pressure to blow by.

 

[Miro 0606]

Sorry forgot to mention I replaced the radiator cap.

 

[brucemillar]

Sorry forgot to mention I replaced the radiator cap.

Have you had a pressure test?

Have you calibrated the gauge?

How are you reading the overheat? If it is only from the gauge and you have no coolant loss and no visible sign of leakage? The the gauge should be considered suspect.

You should also try an infrared thermometer. That will allow you to see exactly where the temps are at in part of the engine/system at any time.

 

[Miro 0606]

I haven't done the pressure test yet. It is the next thing on my list- never done it before any advice would be appreciated.
The gage reads correct. There's no visible coolant loss.
The car is steaming hot I checked the temperature manually. I will try to check the temperature with infrared Thermometer, what should I look for?
Thanks

 

[brucemillar]

I haven't done the pressure test yet. It is the next thing on my list- never done it before any advice would be appreciated.
The gage reads correct. There's no visible coolant loss.
The car is steaming hot I checked the temperature manually. I will try to check the temperature with infrared Thermometer, what should I look for?
Thanks

Okay.

1) Boil a kettle and point the infrared thermometer into it. It should read 100 Degrees C. But whatever the reading remember to add or subtract the difference when you measure at the engine.

2) Run the car up to 'normal' temp.

3) Point the thermometer at the top hose and read it.

4) Point at the top of the rad.

5) move down the rad going side to side. You are looking for any cold spots that will indicate a blocked or sludged rad.


Basically you should see the temps lower as you go drop lower for the top end to the bottom end. Most cars will sit at around 90c with antifreeze added 50/50.

 

[LvR]

IMO with no coolant loss as stated, all the tests already done and all the parts replaced there can only be one answer ...................

My guess is the engine was run on a pure water diet over the years iso a coolant mix that would prevent rust - the result is that block's internal coolant passages are now covered in rust that is acting as an insulator and all the new stuff in the world will not be able to remove any more heat from those contaminated surfaces.

Plausible?

 

[brucemillar]

IMO with no coolant loss as stated, all the tests already done and all the parts replaced there can only be one answer ...................

My guess is the engine was run on a pure water diet over the years iso a coolant mix that would prevent rust - the result is that block's internal coolant passages are now covered in rust that is acting as an insulator and all the new stuff in the world will not be able to remove any more heat from those contaminated surfaces.

Plausible?

It is plausible, very plausible. A good strong coolant flush left in for a couple of days should clear most of any build up. In my experience most of these issues are simple fixes with some being quite humorous.

* Blocked heater Matrix.
* Rad Cap.
* Viscous or electric fan blade re-fitted back to front.
* Viscous fluid dried out.
* Unseen micro leaks, allow the pressure to escape and lower the boiling point.
* No overheating but a poorly calibrated gauge (this is very common).
* Running AC with hot weather and a lack of fan cooling.
* Debris. between the AC condenser and the Radiator
* Blocked Radiator Core.

A pressure test may/should expose any leaks. You can get a bright dye added to the coolant to spot any leaks. A compression test my highlight leaks around the head.