Hello all, I'm new to these forums but have been reading back posts to try and figure this out. No luck so here goes:

I've had my 94 F150 4.9 300 for over a year, bought it off a buddy to use for work. As soon as I got it I flushed the coolant, transmission, etc, etc. It runs great with no problems... till now.

I noticed the temp gauge was all the way up and was about to over-heat. So I shut it down and let it cool. After checking the coolant level (there was none in the radiator) I went and filled it up with coolant/water. I quickly noticed it was leaking from somewere under the intake manifold and above the exaust manifold.

Head gasket right? I'm not so sure. The leak only appeared once and looked like it was pissin out of a small hole, after filling it and driving home (about 15 min away) I checked it again and it wasn't leaking anymore.

So here is my question: Is there some kind of a freeze plug under there or something else that will open and then close? I can't actually see the hole itself.

Sorry for the long post, and thanks in advance. I figure if anyone could help it would be someone in here.

 

I don't know of any freeze plugs or other wise in that area. It's not mixing with any Other fluids is it?

 

its not mixing with anything I can see. When I put in the anti-freeze it came back out just like it went in. I just got back from dinner and it never leaked or over-heated. Go figure. I even idled it for about 15 min with the AC on full blast. I'm sure it will raise its ugly head at the worst possible moment. It's almost gauranteed to happen now that I said it. DOH!

 

Man you said it. How about pressure on the system? Does it build up when its hot like it should is the rad. cap in good condition?

 

radiator cap is good,I think, I replaced the therastat last year about this time. It wasn't even warmed up when I went to fill it the first time. So I guess system pressure wasnt the issue (?).

 

Well I was just wondering if it ever reaches full pressure cause if it does not it may not leak but if it does and does not leak well I think you see where I'm going. It may not leak unless it builds normal pressure which is like14-16psi I believe.

 

I'll go ahead and pick up a new cap tommorrow. Can't hurt I suppose.

 

Right or inspect the old one. Years ago we used to test them at service stations but I haven't seen this done in a long time. IF you determine the cap is good OK. We used to test the radiator the same way in fact with the same tool but as I said I haven't seen or needed this in a long time. Thinking is to build up full pressure on your truck and look for the culprit. Good luck.