HI. My car is a 87 300d with the #14 Head.
I've put 13,000 miles on it since I bought it. Changed the oil from dino to 15w-50 mobile 1. Maybe used a qt in 5,000 miles. I also put a new thermostat and flushed the coolant system because I wasn't getting any heat. Didn't fix it but a new radiator cap did. Now anytime I open the coolant tank cap there is a "sshhh" of pressure releasing. I don't lose any noticeable amount of coolant. I did not lose any in the last 2,000 miles.

I know if the top radiator hose is hard in the morning that can be a sign of a cracked head. My top hose isn't really hard. I can squeeze the top hose sides together. **But if I open the cap on the coolant tank it goes SSHH and realease some pressure. Is this an early sign of the head being cracked?

Example: I drove it about 11 hrs straight on Friday. Got home turned it off at 10pm and at 8am it had a little sshhh of pressure released in the morning with temps staying around 45-50 degrees all night and day.

I drove it for 6 straight hrs saturday - got home at 5 and this morning it was slightly leaking a little coolant from the top radiator hose at the radiator. The temps dropped around here from 45 yesterday to the low 20's.

Thanks in advance and sorry for the long post