jstluise

1987 22RE

I've been curious about my coolant system and if it is holding pressure. When I would remove the cap after the the truck sat for a while (after driving), you wouldn't hear the 'pop' of the pressure releasing.

So, I got a leakdown tester today and hooked it up. I pumped it up to 14 psi and it does have a slow leak. I timed it and it dropped 3 psi in 20 minutes.

The cap is brand new, and it tested good. I also clamped off the hose to the overflow just to make sure it wasn't leaking there.

The radiator was replaced about a year ago with a plastic/aluminum radiator. I have heard complaints about the radiators with the plastic caps. Since I replaced the radiator, I had to top off the coolant once...but I don't know if it was due to loosing coolant or not.

So the best case scenario is that the leak is somewhere in the radiator, then I can just get a replacement since its under warranty. Worst case: leaking into the cylinder. The head was replaced a year and half ago after I blew a radiator hose and overheated. The head is new, not rebuilt.

So, now what? I think it is going to be tough to locate this leak...

Also, what is the typical leakdown specs? Psi/hr?

TNRabbit

You should be listening for the leak while it's leaking down. I can't imagine that small of a leak isn't coming from the tester itself. If you had even a SLIGHTLY significant leak, you'd hear it escaping.

jstluise

Okay, well first off I'm an idiot. I tested the system when the water was still warm. So....just the cooling of the water itself explains the drop in pressure.

I waited until it was all the way cool and re-tested. This time, it dropped just under 1 psi in 1 hour (instead of 3psi/20min). And the best part is I spotted a puddle of coolant on the ground. It looks like my lower radiator hose connection (radiator side) is leaking just a little bit. Under 14 psi, it was enough for it to push some water out.

I am going to conclude that the slight pressure drop was from the leaky connection, and that after snugging up my hose clamp I should be good to go.

Makes me feel better...I've been paranoid about cooling ever since I overheated cracked the head!

scope103

This page http://personal.utulsa.edu/~nathan-b...47descript.pdf says the coolant cap is supposed to open when the pressure exceeds 8.5-14.9psi. In other words, you pressurized it right up to or past the limit. (and no leak-down spec is given).

I agree that 3psi in 20 minutes sounds pretty good. I assume that you have no visible leaks (so the radiator is not leaking below the fill line, which is within the top 1/2 inch of the radiator). Do you have any symptoms of leaking into a cylinder? (White smoke that feels damp, not oily, and persists past the first 60 seconds of running; one (or two ...) really clean spark plugs with no carbon at all, ...)

When you tested the cap, did it go all the way up to 15 psi? (8.5 is still w/i limits http://personal.utulsa.edu/~nathan-b...53services.pdf) Did you leave the cap on the tester for the 20 minutes?