Cooling project - have some questions

'88 4.0L New 3-row radiator without a pressure neck.

I currently have the fun pressure bottle by the firewall which I want to replace with a Moroso bottle. (p/n: 14651) It comes with: A 1/4in. pipe overflow fitting at the neck, a 1/4in. water intake fitting, and a 1/2in. pipe fitting at the bottom. It accepts a standard size radiator cap.

Question #1) What pressure radiator cap do you think I shoud put on it?
Question #2) Do I also need to install an overflow bottle and run a hose to the "overflow fitting" or should I just cap that opening off?
Question #3) Do you think this will work - did I miss anything???

Thanks...

http://jeepsunlimited.com/xj/cooling/cool.htm

http://www.madxj.com/MADXJ/technical/technicalfiles/JTopenSystemSwitch/OpenSystemSwitch.htm

http://www.geocities.com/chmwatson/FAQs/Jeep/radconv_overflow-bottle.html

Of course it will work -- I've been running a Moroso tank in my '88 XJ for years. I found (after considerable searching) a small-ish overflow/recovery bottle that fits between the air box and the fender. The threaded hole in the Moroso cap neck accepts a standard "barb" fitting that you can get at Lowe's, Home Depot, or any plumbing supply house. Run a tube from there to the overflow bottle and you're done.

I'm running a 17-pound cap because that's what the guy at the speed shop recommended, but I think when I replace it I'll drop to maybe 15 psi. If I can determine what the factory uses on the newer "open" systems, that's what pressure I'll use on mine.

Eagle,

I was looking at this link and it sounded interesting:
http://www.madxj.com/MADXJ/technical/technicalfiles/JTopenSystemSwitch/OpenSystemSwitch.htm

I was concerned about trapped air in the radiator and upper radiator hose. Should I be concerned about trapped air if I just replace the bottle? Would putting a fitting in the upper radiator hose eliminate the trapped air?
Thanks...

Cooling-Overflow

The question #2 regarding the overflow:
I would not cap of the overflow port because then you will have no means of pressure relief should you pressure cap be activated. Whether you plumb it to a bottle or not sort of depends on how often you check your coolant level. You know all those good old early 70's and previous cars had no overflow tank, simply a rubber hose to the pavement. If you can find a convenient spot its extra insurance to have a reserve supply. In a sense, you and I have no overflow right now. If the pressure rating of that dumb plastic cap is exceeded the antifreeze goes on the ground.

RTicUL8 said:

I was concerned about trapped air in the radiator and upper radiator hose. Should I be concerned about trapped air if I just replace the bottle? Would putting a fitting in the upper radiator hose eliminate the trapped air?
Thanks...

Click to expand...

Replacing that plastic POS with a Moroso tank has no effect on trapped air. The Moroso tank functions exactly the way to plastic tank did, only better. You still need to "burp" the system if you drain and refill it.

Aside from the fact that you get a real radiator cap with a decent seal when using the Moroso tank, you also get additional advantages. The factory bottle also functions as an expansion tank, so it is designed to be filled halfway when cold. If you equip the Moroso tank with an overflow/recovery bottle, you can keep the tank itself completely full and eliminate all air from the system. As Art mentioned, you will also have a catch bottle, so you no longer lose coolant if it expands too much. In fact, it will function as an "open" system, without the hassles of figuring out how to control the aux fan -- and it puts the radiator cap at the high point of the system, which is where it wants to be.

Dose anyone know an online source for those Moroso bottles, if not where are they, or a cheaper metal alternative available?

I bought from summitracing.com I got the expansion tank p/n: MOR-63651($99.95), the overflow bottle p/n: MOR-63657($26.95), and a 16lb. pressure cap p/n: MOR-63316($9.95). I'm going to get the hoses and fittings locally. They should arrive today, so I'll post the results tomorrow.

RTicUL8 said:

I bought from summitracing.com I got the expansion tank p/n: MOR-63651($99.95), the overflow bottle p/n: MOR-63657($26.95), and a 16lb. pressure cap p/n: MOR-63316($9.95). I'm going to get the hoses and fittings locally. They should arrive today, so I'll post the results tomorrow.

Click to expand...

That's a much better price than I paid locally.