I would try a OEM cap just for the hell of it, plus pressure ck the system for leaks.Something is definitely not right

 

I agree with the recommendations to use worm style clams. The hose ends seem to widen over time and the stock spring clamps aren't enough to hold the coolant inside. That has been my experience anyway.

Have you tried using a vacuum gauge to test for leaks? The procedure is outlined in the tech folder.

 

No, sorry, that 193 was on my 100 mile trip to Charlotte. I'll have to look, I think on the grade you are referring to, my ECT got up to 205 in 3rd Gear driving about 3000rpms. It immediately dropped though, by the time I got about 3 or 4 miles, it was back down to 190.

Yeah, maybe it was my gauge? I'm hoping.

Thanks Mark. I am pretty sure I did this last time. I released the pressure and I was confused as to why it dropped to zero and stayed there until about 5 or 10 minutes later? I remember romping on it and the needle didn't move and thinking "Oh great, what now?" Then I remembered I had opened the cap. I've done so much 'stuff' on this truck since I bought it, it's hard to remember though, so I will do it again on friday.


Below the min line, maybe 1/8". It never leaks out of this cap. There is nothing on or around the degas bottle. I have a sticker on mine, which I understand is the 'new' max line.


I have it teed from the degas bottle to the radiator, in-line with the Sinister Coolant Filtration line. I put a 3" 3/8 hose on the degas bottle and an inline tee from there connected to the radiator. Then I connected 8 feet of 3/8 fuel line to a 1/4" NPT brass fitting with a 2 1/2" 60psi gauge I purchased from Tractor supply. I dropped the gauge when I was pulling it off of the truck windshield wiper arm where I had it resting while driving, so I was SOL to perform the test again.

No, I have a worm style clamp at the top where it is leaking, and the spring style clamp is at the bottom too, where it is leaking at the thermostat housing. It is also leaking at the brass tee where the sinister coolant system taps into the degas line to the radiator. It is not leaking from degas bottle though where spring clamps are used for both lines (intake and radiator)

I purchased an OEM cap after originally purchasing a Stant cap and having it pressure checked for 15-16 psi. It appeared to work, but bought the OEM 'click style' just in case. My stant didn't click when it screwed on.

 

Also, not trying to threadjack, but what is the danger of running a cap that pops at 20psi? I tested my new cap straight out of the package from Ford and it popped at 20psi. You have me nervous now....

Maybe under heated conditions it behaves differently

 

4 psi more max pressure on everything but a higher boiling point also. FWIW--if your head gaskets and EGR cooler are mechanically intact the 16 psi should be more than adequate. I was having a high boost puke and wanted to see if the higher PSI cap would stop it, which it did. I need to get a new cap but haven't had time (or the inclination) to go the local Ford place and let them have my money. I'm waiting for a trip to Little Rock during the week.

I'm also wondering if there was a manufacturing change made to the correctly spec'd cap unbeknownst to the general public, similar to the oil cooler change.

 

Nothing wrong with that. IIRC that's about a 7 mile 6 or 7% grade. We used to do our test and tunes there when I lived in Hendersonville.

FWIW--Before dropping a chunk of cash on anything else, it might be worth the coin to invest in a pressure testing kit as was previously suggested. You can pump it up to see where and what's pushing coolant at what pressure and why. It will also tell you what pressure your cap pops at. That would also give you a way to verify that your pressure gauges match. These days it's so freakin hard to know that you're getting a quality instrument.

 

Should I buy or just rent? I had the cap tested, but I guess it would be a good idea to rent the O'Reilly's cooling system pressure tester. They told me it would be $150 and then I would get my money back when I returned it. I have never used the tester other than for caps. Do I just screw it on to the degas bottle and pump the system up to 16 -18 psi or so and see if it leaks?

 

Rent it. It's not going to be something you would use more than once or twice ever, I wouldn't think.

Most just screw onto the degas bottle or radiator directly but you may have to plumb it in somehow. I guess it depends on what they have in the kit.

 

Yeah, they have the kit with the Ford adapters for the degas bottle and degas cap. I will rent it and see what I can come up with.

 

This is dang near impossible to see, but if you open it up full screen, you can see the coolant leaking from the upper hose. After I got home, I tightened the hose down using a ratchet and 8mm socket and tightened it until it stopped, without cranking down really hard. I would guess it went 1.5 turns more? I was afraid to really drive it after that because I thought maybe it was a good thing that the pressure was leaking instead of blowing this new radiator. I like the pressure test now. Sorry I missed that last time. I'll pump up the system tonight and see what is going on.

 

I've never driven any length of time with a pressure gauge attached to the cooling system so I don't know how it would respond. The only time I did that was to check for blown headgaskets since the truck was puking out the cap anyway. Since the gauge went over 16 fairly fast the diagnosis was easy. That may be something I need to do just for grins, giggles, and future reference. I personally wouldn't worry about blowing an aluminum radiator at 20 psi. I'd think it would take quite a bit more but I may be thinking wrong. I know that a lot of people don't like spring clamps because they can't crank them down. I like them for the fact that they don't ever loosen up BUT it seems that once they get "seated" in a particular position on an old hose they like to stay in that position. I guess both types have their pluses and minuses

 

Bottom line in my op. is if you have a 16# cap working properly and your leaking at hoses, the clamps and/or hoses are the problem. I'm running a 20# cap on my 428cj engine with aluminum radiator with no issues at all. Stock cap was 16#.

 

I monitor my degas bottle pressure continuously.

It is slow to build pressure and slow to drop off.

It is proportional to the coolant temp, unless you really romp on it and then you get a spike of a few EXTRA psi. These drop down to normal again after about a minute.

 

Mark, if the cap is working properly shouldn't it relieve itself? Don't think springs have built in time delays? Should be instantaneous in my op.

 

I never reach the cap relief point. I run 8-9 psig almost all the time. I can get it to spike to 11-12 psig if I make a WOT run from a standstill. Once I reach 75 mph and hold it, it slowly drops back to 9 psig.

There is quite a bit of instantaneous heat from a WOT run. That heat, and maybe even some flash boiling on the surface of cooling surfaces, causes this momentary spike of 2-3 psig.