300SDL Running Hotter than Normal - PeachParts Mercedes-Benz Forum

wgilmore · #1 02-05-2009, 05:28 PM

My 300SDL finally back on the road , is running hotter today on a nice cool 70* day than in the middle of summer on a 100* day with the A/C on.
I replaced the fan clutch, fan blade and thermostat about 2 years ago.
Just finished replacing the head gasket, added coolant through the coolant tank.
Went through the process of filing , and adding more , running the heater, adding more coolant until the system I think is filled.
Yet , out on a drive down the freeway after 10 minutes, with no A/C on, I'm at
95 + degrees, then come to a stop and nearly hits 100* .
Did not do the fill through the upper radiator hose.
Checked the fan clutch at about 90* on the gauge and the fan free wheels for a few seconds after shutting the engine off.
Any ideas?
Thanks

oldsinner111 · #2 02-05-2009, 05:33 PM

Maybe a good flushing is needed.I know these guys will start crap over this,but I flush with thermo out driving car a hour with 50/50 water,an vinegar. always works for me.With a aluminum head you will need it to cool down before draining and flushing with water hose.I've used it for years.Besure and have heat on to flush heater core.

sixto · #3 02-05-2009, 10:52 PM

Did you clean the radiator and evaporator cores? How old is the radiator?

Sixto
87 300D

Brian Carlton · #4 02-05-2009, 11:05 PM

Quote:

Originally Posted by wgilmore

Did not do the fill through the upper radiator hose.

Any ideas?

Thanks

Asked

Answered

You're welcome.

wgilmore · #5 02-06-2009, 01:54 AM

Quote:

Originally Posted by sixto

Did you clean the radiator and evaporator cores? How old is the radiator?

Sixto
87 300D

No I didn't clean the radiator or heater core, since the system was cooling fine over the summer and into fall. The car has been under repair since September.
The radiator age is unknown , but it is not the original OEM, it was replaced with a MB radiator by the previous owner.
Makes no sense to me that the car cooled fine until September when I removed the head and various other things, put everything back together - correctly.. now it runs at 100 degrees in winter.

wgilmore · #6 02-06-2009, 01:54 AM

Quote:

Originally Posted by Brian Carlton

Asked

Answered

You're welcome.

Meaningless. Thank you.

Brian Carlton · #7 02-06-2009, 02:03 AM

Quote:

Originally Posted by wgilmore

Meaningless. Thank you.

You stated that you did not fill through the upper radiator hose.

You then asked if we had any ideas. Clearly, you had doubts about your procedure.

You asked a question and answered it yourself. Your problem is the failure to properly fill the head with coolant. The thermostat blocks the capability to fill the head until the thermostat opens. Then, all the trapped air must slowly escape via the expansion tank. It's a very inefficient way to bleed the system.

If you fill the upper hose, the coolant goes right to the head and the air in the head is immediately displaced. The engine will then run at the proper temperature immediately.

wgilmore · #8 02-06-2009, 02:26 AM

Quote:

Originally Posted by Brian Carlton

You stated that you did not fill through the upper radiator hose.

You then asked if we had any ideas. Clearly, you had doubts about your procedure.

You asked a question and answered it yourself. Your problem is the failure to properly fill the head with coolant. The thermostat blocks the capability to fill the head until the thermostat opens. Then, all the trapped air must slowly escape via the expansion tank. It's a very inefficient way to bleed the system.

If you fill the upper hose, the coolant goes right to the head and the air in the head is immediately displaced. The engine will then run at the proper temperature immediately.

Thanks...
I just tested my thermostat per a not so well informed friend and of course it is fine at 185-190 degrees. Opens nearly 1/2" - promptly and closes etc..
This same person indicated that I did not need to fill the cooling system via the upper radiator hose .. that this was absurd.
Same person says the 2 year old OE fan clutch would be the next suspect.
I don't think so though. I don't think enough coolant is flowing to raise the
radiator temp to fully engage the fan.
From your comments and others it appears that it is critical to fill the head first.
I will refill the coolant by filling the head and then fill the expansion tank.
Thanks again , didn't mean to get snippy... this has been a very long and painful project ...
I will post my results, though I guess everyone on the forum has already been down this road and would probably be a waste of storage.

t walgamuth · #9 02-06-2009, 06:04 AM

Brian is right. Clearly the car cooled fine before you removed the head. Just sitting there did not affect your car's cooling ability. Its most likely a large bubble of air trapped in your system.

Brian Carlton · #10 02-06-2009, 09:58 AM

Quote:

Originally Posted by wgilmore

I will refill the coolant by filling the head and then fill the expansion tank.
Thanks again , didn't mean to get snippy... this has been a very long and painful project ...
I will post my results, though I guess everyone on the forum has already been down this road and would probably be a waste of storage.

You don't need to drain anything. Just pull the upper hose.........pour in coolant slowly until it's totally full..........and reconnect hose quickly to radiator (try not to lose any coolant).

The only thing you wish to do is to fill the head and displace the air.

Please post your results...........the more data we get.........the better we get at fixing by wire.

Oh, and with regard to "friends"..........unless they actually own one of these vehicles and have worked on them..........don't take any advice.

wgilmore · #11 02-06-2009, 02:06 PM

Quote:

Originally Posted by t walgamuth

Brian is right. Clearly the car cooled fine before you removed the head. Just sitting there did not affect your car's cooling ability. Its most likely a large bubble of air trapped in your system.

Yes, you are right. I agree . There is no other reason for the SDL not to cool correctly. Radiator still has a new looking inventory code sticker on it from MB.
New fan clutch and fan, new thermostat that is functioning correctly and yes,, it did cool well last time it ran. Passages in the head are all very clean, just don't have the build up of crud in the cooling passages.
I hope that the temperature on the gauge was correct and did not indicate a temperature lower than the actual temperature due to the air space in the head. My concern is that if the air pocket was sufficiently large, it may have reduced the liquid contact area on the sensor and give a false low reading.
The sensor for the temperature gauge is in the head and the sensor in the upper radiator hose neck is for the EDS .

Brian Carlton · #12 02-06-2009, 02:11 PM

Quote:

Originally Posted by wgilmore

I hope that the temperature on the gauge was correct and did not indicate a temperature lower than the actual temperature due to the air space in the head. My concern is that if the air pocket was sufficiently large, it may have reduced the liquid contact area on the sensor and give a false low reading.
The sensor for the temperature gauge is in the water neck of the upper radiator hose and think the sensor in the head is for the EDS .

The sending unit provided the proper temperature of the coolant at the location of the sending unit. If air is trapped in the head, the temperature of the aluminum at the location of the trapped air is significantly higher than the temperature at the location of the sending unit.

wgilmore · #13 02-06-2009, 02:14 PM

Quote:

Originally Posted by Brian Carlton

You don't need to drain anything. Just pull the upper hose.........pour in coolant slowly until it's totally full..........and reconnect hose quickly to radiator (try not to lose any coolant).

I understand that I didn't need to dump the coolant, but I had already done that to test the thermostat.

Quote:

Please post your results...........the more data we get.........the better we get at fixing by wire.

Yes , absolutely will do.

Quote:

Oh, and with regard to "friends"..........unless they actually own one of these vehicles and have worked on them..........don't take any advice.

Yes , you are painfully correct, as I am learning over time, the SDL is a unique machine. The best intentions / knowledge of those who lack direct and long term experience is often a trip down the road of "do over".

Brian Carlton · #14 02-06-2009, 02:21 PM

Quote:

Originally Posted by wgilmore

Yes , you are painfully correct, as I am learning over time, the SDL is a unique machine. The best intentions / knowledge of those who lack direct and long term experience is often a trip down the road of "do over".

When you need advice.........you come here.........and you read the posts from the members who own one of these vehicles (an SDL). From an engine standpoint, you can also take the advice of those with a W124 that has the same engine (603).

compu_85 · #15 02-06-2009, 02:34 PM

I don't understand why people are so against filling from the upper hose. It's so simple to do, and I found I had an air lock on my car until I filled from that location.

It is possible for the factory manual to be wrong, ya know......

-J