Hey all, been awhile since I've been on here. Hope everyone's good. I've got a 90 300, and until the thermostat opens, the upper hose gets super stiff. I had to replace the rad due to a leak, thats when I noticed this. I thought maybe I put the new thermostat in backwards, took it out again, it was fine. Re-installed a new thermostat, thinking maybe the new/old one was defective, same thing. As far as I can tell, the hose is full of water, but I haven't burped the sysem. (Don't know how.) I'd imagine that would have happened naturally by now. It's actually moving the hose off the rad and thermo housing, the pressure is so high. Any ideas? Talk to ya' later, Peace, Dave.

 

Sounds like a bad radiator cap. What PSI cap do you have?
It should keep the pressure in the system at that pressure.

 

Hey subford, thanks for the idea, I went out today at lunch and checked it. I've got a 13# cap on there, just what was on it when I changed it. I did notice, however, that when I turned the cap over and looked at the rubber, the imprint from the rad outlet wasn't centered on the post of the cap. Turning the rubber showed the post turning off center. I don't know if maybe that would be enough to cause the cap not to operate properly or not, but I did put the old one back on. (Had it as a spare on the heater core box.) I'll post back and let you know what happens. Thanks again, Peace, Dave.

 

Hey subford, I feel like a dunce. I was imagining everything that could be wrong with it, instead of the one thing it probably was. The reservoir would fill and drain, so I figured the cap was fine. Tonight when I got home from work, I popped the hood and gave the hose a squeeze, and there was a little give to it. Hopefully problem solved. My thanks to you. Peace, Dave.