1985 R Model with Anti-Freeze leaks

[Mack458]

I have a 1985 R Model Mack with a Swab rescue body that is my hobby truck. It has a Mack EM6T285 motor. I have had the truck 11 years, and it has always been kept inside.

About 7 years ago I removed the radiator to have it cleaned and tested although it was not having any issues. Last summer while going to an event it started to leak a small bit of radiator fluid at the firewall. I replaced all of the heater hoses and clamps and have had no leaks. All in all, I have had zero issues with the cooling system - until now.

The truck now stays in a pole barn that stays in the 30's without heat. 

A few weeks ago, I took the truck out for a ride, made sure it reached temperature, and put it away. I went into the pole barn about a week later and found a puddle of radiator fluid under it with no indication where the fluid leaked from. I removed the radiator cap, which still had pressure on it, and filled the system with 50/50 mix of fluid. Took another ride to temperature, put the truck away and checked it over for leaks - nothing. Three days later I have fluid leaking out of the pole barn doors. This time I found the leak from a hose clap on a tube the sits vertically near the water pump. Clamp was tight but I gave it a small tighten to stop the leak. Again, found pressure on the cap. Refilled system.

Las week I took the truck for another ride to temperature and put the truck away. Monitored for leaks - none. Three days later found leaks at two different hose clamp locations. Checked back today and the block was wet on the left side of the engine, with evidence on the floor of additional leaking. Removed cap and found that to still have pressure on it.

I checked the coolant today and it reads good to -10 degrees. Can anyone shed some light on what is going on and what I need to do to repair or diagnose this issue?

Many thanks in advance, Mark

[Joey Mack]

Have you used a coolant pressure testing tool ? You can test it cold and save a ton of time. It sounds like you have a few cold water leaks. I would wash the engine off and do your best to wash the anti freeze trails off the engine so you you dont chase old leaks.. Harbor Freight has a decent set for cheap money.  Lets see what the dog pound says on this one... Jojo

[Joseph Cummings]

51 minutes ago, Mack458 said:

Swab rescue body

Had to look that up lol

[tjc transport]

first thing that comes to mind is release the pressure from the coolant system after shutdown  when parking. this would reduce coolant being pressure forced out of the system. 
then as Joey said, do a cold engine coolant pressure test on the clean engine to see if you can find any leaks. 

[JoeH]

I bet it's leaking on the water manifold hose (left side). There's a hose that bridges the manifold from one head to the manifold on the other head. It can be hard to keep this tight.  Likely in the colder temps the metal is shrinking. One of our trucks has done this. No leaks in the summer, then minor weeping in the winter.

Edited 9 hours ago by JoeH

[Mack458]

Thanks, gents, for the suggestions. I will hit Harbor Freight tomorrow. There have been several leaks at hoses and never the same one twice.

I'll let you know what I find out.