Been battling cooling system gremlins lately...new cap(s), new t-stat (motorcraft) and haven't been able to put it to the test yet since the new t-stat. Seems to be running cooler, but, a proper pressure test on the cap and system would be a good idea. Could ask the A/C guy tomorrow if he can look at it but this is one of those things I'd prefer to test and verify for myself if possible. (That A/C I have no interest in screwing with lol)

I called O'Reily's and they rent this testing unit out, so I went and got it, but it didn't fit the bottle neck or cap after playing around with it for 15-20 minutes so I took it back.




Nice professional quality looking and feeling kit...I might be persuaded to just buy one for myself, but this one wouldn't screw onto the neck even after twisting the "bowtie" to retract the plunger on the coolant bottle adapter. It bottomed out too fast and wouldn't allow the adapter to engage the threads on the bottle neck. It was short by a solid 2-3mm and you'd have to press down on it so hard you'd mangle the coolant bottle and ruin the threads on the neck. Can anybody point me to a kit that actually works well with the 7.3 bottle and cap?

 

I used the Harbor Freight kit when I pressure tested my cooling system - seemed to work well.

Radiator Pressure Tester Kit (harborfreight.com)

 

This one?

https://www.harborfreight.com/radiat...kit-63862.html

This seems like a good idea for a DIY maintenance owner to have at their disposal and test periodically.

If it holds 16psi or so for at least 5 minutes that would be a "pass"? Theoretically it should hold the advertised system pressure indefinitely if it's in good condition right?

 

When i did my cups i needed to pressure test, so i put a pvc plug with a tire valve stem in the heater outlet, because i was replacing that at the time, pressured to 15, and left it for an hour, was still 15, called it good and went on. Its a bit of a hassle, but for 5$ and using the shop vac trick, im pretty sure you could do the same thing, added bonus, you get to test your degas cap as well.

 

That's the one. It should hold indefinitely. I'd probably put it on for 30 minutes at least. Overnight is a good test. Very small leaks around injector cups, for instance, can take a while to register on the gauge.

 

Some of these actually have a cap testing adapter included. That one from O'Reily's didn't work on the cap or bottle neck though. I suppose for that money the Harbor Freight kit ain't a bad deal even if it doesn't have the cap tester. I've bought two new caps in the past 3 weeks, including one from the Ford parts counter about a week and half ago while I was still out in Colorado, so probably safe to assume it's fine. Neither one of them fixed anything so it had nothing to do with the cap at all. It was either the t-stat sticking closed/partially closed, or the system not holding pressure. Already replaced the t-stat and now it's time to verify the system holds pressure.

 

Snap on. Buy once, cry once.

 

I've had a Blue Point from SnapOn since 1980, I think it's going to work out. I do have to use adapters for anything that isn't the standard old style cap.

 

I think I see now what the problem was. That kit O'Reily's lent me actually looks very similar to a Snap on in terms of construction. It just didn't have the right adapter to thread onto the neck of a 7.3 degas bottle. Seems like many of these kits don't include the one we need and has to be purchased separately (The harbor freight kit looks like it does though). For example Snap on makes the TA32A adapter for our application that looks like it would have worked with the kit I showed above, as snap on's own pressure testing kit looks like pretty much the same type of deal. I actually found somebody selling a TA32A on ebay for $40 and bought it for the hell of it. Maybe I can just keep the adapter I need and get the rental kit again. There are a lot of pressure testing kits for good used prices on ebay also I saw.

https://www.ebay.com/itm/296428362682

 

I had a pressure test system when I owned the shop that I never reached for. Just squeeze the hose. If it's tight, system is good. If it's squishy, buy a new cap. Or if there's a leak and pressure won't build, it will be obvious because of the coolant on the ground.

 

Cap’s been replaced twice already, the last one from the Ford parts counter. I am placing the chances of getting two bad caps in a row at near zero. It’s possible there was nothing wrong with old-old one I threw away a couple weeks ago.

I’m also not convinced yet there was anything wrong with the thermostat that was in there either, but I threw another one in anyway a couple days ago. For $50 bucks not a big deal.

Now it starts to get a little expensive to just go blindly throwing parts at it. Up next would be the degas tank itself. There’s mild suspicion there and it wouldn’t surprise me if it quit holding pressure somehow a few weeks ago when I was out west after 100k miles, as these replacement OEM units have been known to be trouble makers, but I want to see a confirmation the system isn’t hold pressure while the engine is off and cool.

 

It doesn't take much but a pinhole leak to prevent it building pressure. All I can think of is if your upper hose is still squishy like it's ambient pressure, then the system isn't completely sealed up somewhere. For instance, I went through two Motorcraft coolant reservoirs straight from the local Ford dealer here that had a flaw in the seam where they glued the upper and lower halves together. Finally gave up and bought an aftermarket tank that held pressure, but would start getting cracks on the inside of the container that I could see looking from the outside in on the body of the tank. Bought another tank from I forget where and it's holding just fine with the radiator hoses nice and tight when the engine is up to temperature. I guess you could get a tester to try and pressurize the cooling system, but I've been under the hood for 45 years and never found that I needed one unless I was needing to see if a head gasket was still good or not. Even then it was easier to pull the oxygen sensor out and look for the stain that the coolant left behind on the sensor. What I would recommend right now is get a tee that can be installed on the return hose that goes to the coolant tank and run some compressed air to the tee. The radiator cap will protect the system from overpressure. Add air until either the cap burps like a pressure cooker, or you are able to find the leak.

 

well, I don’t really have access to shop air but that’s a good idea to pressure test the tank and cap. Problem is with a bad tank you very well won’t see a liquid leak during a pressure test if the tank is compromised at the seam since the coolant usually sits below that level. It would just be air escaping, which I think I may have heard already squeezing the upper hose a bunch of times. A solid aluminum tank would theoretically be better in that regard.

 

Something like this is all you need to provide air pressure. Plus it comes with a gauge so you can see how much pressure is on the system. For $6.97 at the time of this writing, yeah it's not expected to last long. Even a hand pump for a bicycle tire is all you really need.
https://www.harborfreight.com/12v-po...tor-63152.html
Get 15 psi on the system and start running your hands around all the seams and connections. Spray soapy water if needed.

 

O"reilly does have the correct adapter, but it's separate from the kit. They don't know they have it though, I had to research it, find it, and go back to the store with the part number then they dug it out for me and it worked.. I made a post all about it here some years back and later today I'll see if I can find it.