87 300d: Changed thermostat, over heating worse - PeachParts Mercedes-Benz Forum

Sbucha · #1 08-25-2011, 05:47 PM

Before i put the new one in I dropped the old and new into water on the stove to check operation. New one opened sooner and stayed open longer and opened at right temp. I put the new one in and the car overhears really fast, before it was drivable just got hot on long hills in second gear. I put it in facing the same way as the old which was with the large spring and valve facing away from the water pump, opening away from the water pump. Is this wrong, if not what else could explain this rapid change?

1975300D · #2 08-25-2011, 06:04 PM

Normally, the side with the spring goes down into the housing. Is that how you have it?

Sbucha · #3 08-25-2011, 06:29 PM

I put the t-stat with the spring inside the housing. The housing attaches to the water pump, so the spring and valve face/open away from the water pump and into the housing.

1975300D · #4 08-25-2011, 06:35 PM

Sounds right. My 115 was overheating so I had to elevate the front end, disconnect the heater hose that goes into the firewall, and let the air bubbles escape out the rad cap while adding more coolant down the hose.

I'm sure other posters with your car can help you better.

Brian Carlton · #5 08-25-2011, 06:48 PM

Put the vehicle on an uphill incline or on ramps.

Disconnect the radiator hose at the radiator and fill the hose with coolant right to the end of the hose.

Quickly reinstall the hose onto the radiator...........losing as little coolant as possible (the uphill thing works great).

Drive it and check the temperature.

winmutt · #6 08-25-2011, 07:13 PM

They are supposed to be self purging. When you refilled with water and engine running did you turn on the heat, drive around and top off?

If the radiator is old I would replace on principal. The last thing you want is overheating on a 603.

Brian Carlton · #7 08-25-2011, 07:17 PM

Quote:

Originally Posted by winmutt

They are supposed to be self purging.

I'd sure like to see how the air gets purged from the head if the system is filled via the expansion tank (the fluid goes down to the bottom of the radiator and creates a massive airlock in the head.

Although it might purge once the thermostat opens, the head could easily cook before that happens...........and hence the reason for the very high gauge temperature.

Sbucha · #8 08-25-2011, 07:20 PM

I did turn the heat on and drive around and refill. I'll try purging the air when I get home.

winmutt · #9 08-25-2011, 07:27 PM

Quote:

Originally Posted by Brian Carlton

I'd sure like to see how the air gets purged from the head if the system is filled via the expansion tank (the fluid goes down to the bottom of the radiator and creates a massive airlock in the head.

Although it might purge once the thermostat opens, the head could easily cook before that happens...........and hence the reason for the very high gauge temperature.

FSM specifies that when engine reaches 60-70*c to close off the filler tube from the expansion tank (I guess they mean pinch it off). This probably forces water into head?

You make a very good point of course.

sixto · #10 08-25-2011, 07:27 PM

Is it sufficient to remove one of the temp sensors on the upper radiator hose fitting while filling through the reservoir?

Sixto
87 300D

Brian Carlton · #11 08-25-2011, 07:43 PM

Quote:

Originally Posted by winmutt

FSM specifies that when engine reaches 60-70*c to close off the filler tube from the expansion tank (I guess they mean pinch it off). This probably forces water into head?

Until the thermostat opens, the radiator and the expansion tank are isolated from the cooling system.

I'm not grasping how pinching the hose would force coolant into the head prior to any thermostat operation...............??

winmutt · #12 08-25-2011, 08:08 PM

Quote:

Originally Posted by Brian Carlton

Until the thermostat opens, the radiator and the expansion tank are isolated from the cooling system.

I'm not grasping how pinching the hose would force coolant into the head prior to any thermostat operation...............??

Im just repeating the good book. Maybe this is why heads crack

winmutt · #13 08-26-2011, 04:35 AM

Quote:

Originally Posted by Brian Carlton

Until the thermostat opens, the radiator and the expansion tank are isolated from the cooling system.

Ah duh, there is a hole in the stat for venting air! Forgot about that.

ds190 · #14 08-27-2011, 06:43 PM

[QUOTE=winmutt;2778465]FSM specifies that when engine reaches 60-70*c to close off the filler tube from the expansion tank (I guess they mean pinch it off). This probably forces water into head?/QUOTE]

You misread that Note. Attached is FSM "Draining and Pouring in Coolant" to clarify.

winmutt · #15 08-28-2011, 04:07 PM

"Close filler connection at expansion tank from a coolant temperature of approx 60-70C"

What exactly is the filler connection?