Hey y'all

Well, I was convinced I needed a head gasket, now maybe not so much...

I did a series of pressure tests on the coolant system...

Here are my findings:

Cold test, pressure to system 15lbs, no leaks no leakdown after 10 minutes

Tested old radiator cap, big fail, leaked badly

Tested new cap, hissed at 13, held 7 lbs

Warm test on engine results:
Start 6:35 pm gauge on cold radiator no pressure
6:38 1lb leak dripping 1 drop per second
6:43 1.5# leak the same
6:45 2# same leak
6:47 4# leak faster drip
6:50 T-stat opens, leak 3 drips per second 7#
7pm 8#, leak still fast

shutdown leak stops immediately pressure in system stays at 8#


So... what do I have here? Thermostat housing leak afterall? Or still a head gasket and why?


Any help would be greatly appreciated!

Thanks

91 F250 7.3 IDI E4OD 4x4 191k miles

 

I didn't see in your post where the drip is coming from...

Not that i know anything about it, but i would think if it were a housing leak, it would leak all the time... :dunno:

 

leeky heater core

 

The leak is dripping from behind the thermostat housing, can't really see where because of the housing, alternator, and vacuum pump. A hint is it is dripping on top of the fuel pump. It only leaks with the engine running, and like i said, the strange thing is that the coolant system pressure test holds solid, cold or hot...

 

check buy there the heater cores hose goings in to the bolck

 

Would the heater hose only leak when running and not on a cold pressure test?

 

pplant leaks can be real wierd I've seen then hold presure for 15 minutes yet its leaking coolant and I've seen them not leak anywhere but presure would drop. You gotta just find where the coolants coming from.

 

yep, true enough, but wanted to make sure I wasn't dealing with a head gasket leak, and so far seems like I am not...
Oh and did I mention my coolant overflow resevior leaks like a gusher? Anyone know where to get a new one or is it a junkyard item?

 

The misting with the time of the engine on your previous post is what points to a head gasket. I would do a compression test not a coolant pressure test.

 

That's what I thought, about the misting, could it also be the vaccuum pump leacking and misting the drops that are falling? I ask this because the vacuum pump is a bit squirly, the PO replaced it it seems, and the pully is bent, and it is right where the leak is, the drops pass right in back of the vacuum pump... hmmm

 

Ok now that you mention the overflow it sounds like a head gasket try filling your rad to the top put a funnel in it and fill it with water start your engine and look for bubles in the funnel if there are bubles you are getting comprsion in the coolant bad head gasket its wierd the the coolant presure tester didn't pegg and wasn't bouncing around like it would with a bad head gasket

 

What year of truck is this again? On my 92 the vacuum pump is on the opposite side of the engine from the thermostat housing.

 

She's a 91, Vacuum pump right under the Alternator.

And yep, ran for 45 minutes, never got more than 8lbs of system pressure, no bouncing, no bubbles in radiator, no white smoke in exhaust, no coolant in oil. I just dont understand how coolant can drip out and yet the system holds pressure cold or hot...

 

My vacuum pump and the ones I have seen is right next to the AC... just to the right of the IP. Anyhow I would for sure check for a leak there, but I would also do a compression test just for peace of mind.

 

You have air discharge from the vacuum pump when the engine is running.
So the air from the vacuum pump could be causing the misting.

Look at the bottom of the water pump neck.
There is a weep hole that the coolant may be leaking out of, while the water pump is turning.

Also check the top radiator hose carefully for a wet spot and the hose clamps on both ends.

The vibration with the engine running may be causing just enough movement in the hose that a weak spot is leaking or one on the clamps are leaking.

I lost a fan belt one time and after that I had a coolant drip when the engine was running.
Held pressure with the engine off.
Drip very slowly when the engine was running.

Found a very small spot where the belt put a little notch in the top radiator hose.
I guess the vibration from the running engine flexed the hose just enough to open the split so a couple drops of coolant leaked out only when idling.
Never did under stand why the pressure did not make it leak.



I was working my hands up and down the hose sqeezing it when I found it.
For a minute I thought I had poked a finger into the hose it was so weak where the belt hit it.

Those numbers don't look like a head gasket problem to me.