Radiator cap leaking?

[bluexpy]

I have a strange problem that i haven't seen before.

The radiator cap is letting coolant seep out the filler neck. I looked at the cap, and it seems OK.

I haven't tested much at this point. What I've found so far is that the upper hose gets pressurized when the engine is getting warm. I did open the cap when the engine was warm, and coolant tried to spray all over before I put pressure back on it with a thick rag. When it's cold, it needs filling up. It only takes a cup or so to come up to the neck.

Is there something blocking it, or..? The hose from the filler neck to the coolant reservoir is intact.

 

[Blacksheep Josh]

with the engine off, try grabbing the top radiator hose and squeezing it, see if you can get any possible air out. maybe try a new radiator cap as well.

 

[bluexpy]

I think there's something blocking something in the cooling system.

I couldn't duplicate the problem by putting pressure on the upper hose.

More volume of coolant spews out the cap now, and I felt the hoses after running it for a minute [from dead cold motor] the upper hose got warm before the heater hoses did. I don't think this is correct.

The thing sat for almost a week, and I can't find any coolant leak from anywhere else.

BTW, the coolant looks dark. Not sure why. It's not rusty orange like a neglected system. It's just plain transparent brown. I couldn't smell any petroleum on the coolant, and it's very fluid.

Think I'll just take it to a shop and be even more poorer.

 

[Cobraguy]

I hate to tell you this in case I'm wrong, but you could have a cracked head or block that is allowing combustion pressure into the cooling system. First thing I would do is get a pressure checker and check your cap. Make sure it's up to snuff and is 15 to 17 lbs. Then put it on the radiator and watch the pressure gauge while you run the engine. See where the pressure goes. You might have nothing more than a bad cap or cracked radiator neck. But where the coolant is that color, I have my fears. You can also have a shop stick an exhaust gas analyzer in the radiator and see if it picks up exhaust gasses.

Funny though that you aren't mentioning anything about contaminated oil. How does that look? I would think you would have coolant in your oil too...so maybe I'm way off base here.

 

[bluexpy]

Oh, no...it is coming out of the cap, all right. The radiator, although plastic, seems to be crack-free around the neck. The cap is the original Motorcraft. I think this is what a neglected piss-yellow G05 looks like?

If it's a cracked head, how long will it take to build up pressure for it to burst out of the cap? IIRC, it just started doing this or it's been that way, and I just happened to notice it recently. Doesn't overheat or anything...I even get good heat. I just realized I haven't looked down the radiator with the cap open to see bubbles.

I also read the front timing cover could be corroded if the coolant is that bad?

Anyway, I decided to take it to a shop and pay out of my ass. Good suggestion on the exhaust gasses. It had an exhaust manifold replaced for some reason early in its life.

 

[bluexpy]

BTW: What is the original recommendation for the coolant? Is it the old fashioned green stuff or the Ford yellow G05?

 

[alohamonte]

flush the system and replace the cap, it's cheap and fast enough. might as well replace the tstat while the system is empty if you havent done that yet.

i use the green stuff.

 

[aldive]

I would replace the cap.

Good luck ....

 

[Cobraguy]

flush the system and replace the cap, it's cheap and fast enough. might as well replace the tstat while the system is empty if you havent done that yet.

i use the green stuff.

I agree. If they find nothing wrong, do as advised here. I would also switch to green coolant if they do an entire flush. Don't mix them. I don't care what they try and say about being compatible. Just do a complete flush and go to the ol' reliable green. JMO....

 

[bluexpy]

Welp, took it home from the shop today. They pressured test and looked all over the places, and there was nothing wrong with it. Pressure test passed, no exhaust in coolant. The cap was the problem after all. The new one [a Stant,yech] was much tighter & stiffer than the old one. Weird.

In my many years of buying well over 50 cars, I've never had to replace one radiator cap & never had problems with them. First time for everything.

I did feel a little hurt back there paying $125 to find what the problem was...but i feel better knowing the cooling system is 100% from people who know what they're doing. All I gotta do is to change the fluid now, this weekend if the rain lets up...

Thanks for the advice, y'all...time to buy some good ol' green coolant.

 

[Cobraguy]

Good to hear! I was suspecting worse. But I believe in keeping it simple. That's why my first suggestion was to check the cap.