MAF issue

[bhonok]

Thanks Oigle. Extremely valuable points and now I see the bigger picture. I will get thermostat A.S.A.P.

 

[bhonok]

Hi folks. I have DIY some modifications to my ML270 CDI .
I completely removed swirl flaps and servomotor, ( shunts were installed before) I removed EGR cooler and piece that connects it to a EGR mixer, I blocked EGR mixer where it connects to a cooler and completely blocked exhaust gases at the flange where I removed EGR cooler.
I reconnected coolant lines and installed new thermostat.
I am back after SCAN. it wasn't Star scanner ,but Bosch. Good news - no fault codes except P1636- radiator fan and P1192- engine oil level sensor.
I will be looking for solutions for fan and sensor, but for now I am very pleased with results of my work, which wouldn't be possible without advise and knowledge that I got from this forum and especially guys like Alex Crow, Oigle and others. I am very grateful. Happy Easter to all.

 

[mattkh]

......Thirdly, the thermo controls the rate of flow of the coolant. Ian.

Hi
Please elaborate as to how the thermostat controls the rate of flow.

 

[oigle]

Hi
Please elaborate as to how the thermostat controls the rate of flow.

If you look at the thermostat, you will see that, even when fully open, the area through which the water flows is much less than what would be the case with no thermostat in place. The thermo is rarely fully open anyway which further impedes the flow of coolant. The whole concept of having a thermo is to control the volume of water flowing through - from none to suitable maximum.
Cheers
Ian.

 

[Alex Crow]

If you look at the thermostat, you will see that, even when fully open, the area through which the water flows is much less than what would be the case with no thermostat in place. The thermo is rarely fully open anyway which further impedes the flow of coolant. The whole concept of having a thermo is to control the volume of water flowing through - from none to suitable maximum.
Cheers
Ian.

And to add to that...

The thermostat will cause as big a restriction as it can, with respect to ECTs.
In doing so it will cause a pressure build up between the pump and the thermostat - this includes the vital cylinder head part of the system.
Thus it will resist higher peak cylinder head temps, as it can go to higher temp without boiling, due to the (significantly) increased pressure (add on cooling system pressure).
This effect is greater at higher engine speeds.

 

[oigle]

Good point Alex. Thermostats are really a vital part of the system in many ways.

 

[mattkh]

......The whole concept of having a thermo is to control the volume of water flowing through - from none to suitable maximum.Ian.

Hi
Thanks. All I want to know, now, is
Does it open from closed to fully open in one second so to speak, or
does it take say 5 minutes, opening 1mm every minute.

 

[television]

The thermostat slowing opens and closes to suit the running conditions, you can count the seconds it takes to go from fully open to fully closed, they can be tested up a cup of water and heating it.

As been said so many time Mercedes stats are very poor and do not last as long as most other makes. My CL is the same year as my V70R and the same mileage, and the CL thermo failed in the CL, the V70R is still perfect.

I do not see how the design of the engine can come into it as the Mercedes versions fail all across the whole range

 

[oigle]

Hi
Thanks. All I want to know, now, is
Does it open from closed to fully open in one second so to speak, or
does it take say 5 minutes, opening 1mm every minute.

It would never open fully in seconds in your engine. It is not time related. It would rarely ever be fully open in Britain. The percentage of opening is related to the temp of the water coursing through. As you reach 85°, it cracks open, allowing a small flow. If the temp then gets to say 87°, it will open further and so on until it is fully open around 95° and then the electric fan (if fitted) usually cuts in to try to keep it from going higher.

 

[mattkh]

......The percentage of opening is related to the temp of the water coursing through.

Hi
So, first thing on a morning, it will be closed fully and No water will be coursing through. Hence the temperature of the water will be picked up by conduction.
This might explain why they misperform.
I think the engine designers should start thinking of electronic temperature sensors to control electrically opening valves.

 

[rpe2]

Hi

I think the engine designers should start thinking of electronic temperature sensors to control electrically opening valves.

What like the heater valve on the 211? That never gave any trouble...

...oh, hang on.....

 

[oigle]

Hi
So, first thing on a morning, it will be closed fully and No water will be coursing through. Hence the temperature of the water will be picked up by conduction.
This might explain why they misperform.
I think the engine designers should start thinking of electronic temperature sensors to control electrically opening valves.

Not quite. Not sure of the Benz ones, but most thermostats have a small bleed hole to allow a very small amount of coolant to flow past the thermo so it can sense the temp of the coolant in the head.

 

[Alex Crow]

Hi
So, first thing on a morning, it will be closed fully and No water will be coursing through. Hence the temperature of the water will be picked up by conduction.
This might explain why they misperform.
I think the engine designers should start thinking of electronic temperature sensors to control electrically opening valves.

As said above, all will have a bleed, allowing a certain amount of water flow at any temperature.
Generally, the thermostat design works very well, as it has for many years.
Yes, we see some failures, but almost never causing overheating...


The electronic 'stat has been partially tried on eg the 272 engine, and I have seen 2x of these fail already.

 

[bhonok]

Can somebody explain function of temperature sensor on thermostat housing.? It doesn't control stat, it is mechanical . Does it control electric engine cooling fan? And if so,does it send a signal to ECU or directly to a fan through some fan controlling module ? Where is this module on ML270 CDI?
Thanks

 

[rpe2]

It tells the gauge on the dashboard how hot the engine is.

 

[oigle]

Boris is having trouble working out what makes his rad fan work. Both temp above 95 will trigger it and also a signal from the aircon when cooling is required.
He needs to know how he can trace these signals - where are they sent from? His electrics have been butchered and the fan works all the time.
Any help would be appreciated by him.

 

[mattkh]

5 volts is the max used in this system, so that is Ok

Hi
In that case, where is the step-down transformer located ?

 

[bhonok]

Hi
In that case, where is the step-down transformer located ?

The MAF itself serves as step-down transformer. It gets activated by 12V power supply from ECU and sends 5v. reference signal and variable voltage signal back to ECU.