More coolant spew
 

When my 86 300E idles for 10 minutes, it starts spewing coolant from the overflow tank. Driving around, this doesn't happen. The hose that goes to the thermostat is rock hard and the hose going to the overflow tank is squishy and limp. I replaced the thermostat last week thinking that was the problem, but obviously that was wrong. Could something be plugged and why only when I am idleing in park? And you don't need to say "don't idle your car dumbass".

Sounds like it's boiling over. check the condition of your radiator cap? If questionable, replace.

Probably has all kinds of air in the system as well.

x2 on the radiator cap.

Also make sure thermostat is in the housing correctly. Sounds like the system is not flowing through the bypass/radiator and building up backpressure. But I work on diesels, so what do I know?

How do i get the air out of the system

Joe, no doubt you realize the spring-loaded side of the thermostat faces into the thermostat housing. Position the thermostat so the air bleed valve is at the highest point ... typically toward the firewall.

It's possible the new thermostat is defective. Hopefully you bought a high quality thermostat - Behr or Wahler.

I always take and drill a 1/8 hole in thermostat to bleed air better.

Top off the coolant tank, turn the Heater to full hot, start car with cap on 1st notch, not screwed on all the way, let it warm up- maybe drive it around the block a few times.

Eventually as the thermostat warms up and starts to open the system farts out the bubble, and the water level will drop in recovery tank. Top it off again, and then tighten cap.

Check levels again in a few days and top off if needed. This may go on for a few days.

Also check the obvious- your fan / fan clutch is working. I would check the lower hose on the radiator while it's running to see if you have adequate pressure coming out.

There should be a considerable difference in temp between the upper and lower hose. If the lower house is still hot, or has low pressure could be a clogged radiator or simply no airflow thanks to a dead fan.

Temp gauge should read accordingly high as well. However if its puking into the tank it's boiling over and it should be in the "red" zone if that happens.

I tried what you all suggested but it keeps boiling over. I checked the thermostat it is a Behr brand and it is in correctly. I ran the car for 10 minutes in park with the overflow cap off and some bubbles came out then it boiled over. About 3 quarters worth of a gallon. Possible bad thermostat still? Or should I try to clean the radiator and how do I do that? Also the interior smells like coolant, so I'm guessing bad heater core, could that be the problem?

yep, heater core. YOu are losing coolant pressure through it, and that's causing your boilover.

Thanks randy. Do you know of any tutorials on how to replace the heater core. I have done this on a Volvo 240 and a Volvo S80, is there much difference on a 300E?:)

apart from the disassembly of the car pain?

Not that I'm aware of- good luck.

PS get the system pressure checked as one last step while you are at it- could be a failing HG as well....

Look up evaporator replacement for a W124.
Best be sitting down.....

BTDT

Jim

By HG, do you mean head gasket?