New Renix Coolant Bottle and Cap problems

[Ecomike]

Objective observation says that if you need to replace the radiator on a closed system, you may as well convert to the open system. The open system seems to be more forgiving. I agree that the closed system is more high tech and is still used by BMW and Mercedes. Question is, on an old vehicle, why bother?

One good reason, which I finally figured out this week. The closed system runs at lower pressures than the open system. The open system runs up quickly to the cap pressure during warm up, releases excess liquid during warm up, but then stays just under cap pressure the rest of the time adding to stress on hoses and radiators. The closed system slowly builds pressure, and only gets close to the 16 lb cap pressure at about 265 F with the 50/50 water/antifreeze mix. The reason for the difference is the air/water vapor in the Renix bottle is highly compressible.

I plan on documenting the actual Renix versus coolant temp pressure curve once I get my new radiator and condenser installed.

I made this discovery last week using a radiator/ radiator cap tester on my Renix system after installing a filler neck in the upper hose that uses a standard radiator cap. The Renix bottle swelled up like a soccer ball between 8 psi and 16 psi! It looked normal at 8 psi. It also took about 25 strokes of the pump to reach that 16 psi pressure in the Renix system (which held leakless for an hour under pressure), versus 2 strokes on my open system to reach 16 psi.

The difference is the compressibility of air, gas versus liquids.

 

[Ecomike]

Ecomike,

I have a spare tank ill take to the hardware store and see what i can come up with.

As far as caps are concerned.. i have yet to actually try the Volvo 940 Turbo cap myself.. but from what i have heard and read it works very well.

Isn't that cap extremely expensive? More so than a clamp?

 

[Muad'Dib]

Isn't that cap extremely expensive? More so than a clamp?

Oh yeah its like 50 bucks or something like that... definetly more expensive than a hose clamp. Its just another option for people who dont like the hose clamp idea. The volvo cap does rate slightly higher psi though... so that could decrease the boiling point just a tad.

 

[Muad'Dib]

For shits and giggles i went to my local Volvo parts place (which also happens to be where you get Jeep Dealer parts) and purchased a coolant bottle cap.

You ask for a 91-95 940 Turbo cap. Dealer part number: 9445462 "Filler cap".

I paid 34.06 for it. Im going to give it a shot and see how it works. It looks like you can find this part number all day long online for less than 10 bucks... but they appear to be knock offs and not a genuine part. I would ass-u-me that buying this cheaper cap would result in the same type of problems we already have with the cheeply made Jeep caps... but i dont know (and wont) for sure.

PS.. this should only be an option if your bottle is good... but you keep going through caps.

Here are a few pics:

 

[Ecomike]

Looking at that cap design from a mechanical engineer design standpoint, the cheap Volvo cap has a good chance of working too. The reason being that the large diameter flat part at the bottom of the Volvo cap will be so much harder to stretch than the bottom of ours. I may buy a cheap Volvo knock off cap and try it, so we can compare results.

 

[Muad'Dib]

Using your logic (which makes complete since) your probably right. Ill keep this thread updated with how the cap works out. Fit great the first time on and tightened completely.

I have still yet to make it to the hardware store to see if i can find a brass insert to work for the bottom nipple of the coolant bottle. Im hoping i can do that within the next few days.

 

[lawsoncl]

Using your logic (which makes complete since) your probably right. Ill keep this thread updated with how the cap works out. Fit great the first time on and tightened completely.

I have still yet to make it to the hardware store to see if i can find a brass insert to work for the bottom nipple of the coolant bottle. Im hoping i can do that within the next few days.

One of mine cracked the lower nipple. I rummaged in my spare plumbing parts and found a brass fitting that threaded in nicely and I epoxied it in place. Lasted about a year until the bottle split open. Dumping hot coolant when it's -15*F really makes a huge steam cloud. :} I gave up since then and converted to the "open" style.

 

[winterbeater]

Ecomike, I admire your perseverence. And I am convinced that you can make the closed system work if you want to keep putting in all this effort. But if you turned your canoe around (figuratively), and put your efforts into an open system, you would have a whole lot easier time.

 

[scottmcneal]

I have both systems, 89 and 94 xj's..My 89 closed system runs cooler in high heat..Closed runs around 210-215.. My wifes(open) runs around 220-240 when it is over 105 degrees when we run slow in canyons.We both have the newer 10 blade fans.(elec)..We both have 185 stats, my rad was roded out and flushed..We replaced hers with a aluminum plus did the flush.. I was going to make mine open till i saw this.I have to say thanks to mike for the hose clamp on the closed system cap, works great still
My 2 cents

 

[Ecomike]

One of mine cracked the lower nipple. I rummaged in my spare plumbing parts and found a brass fitting that threaded in nicely and I epoxied it in place. Lasted about a year until the bottle split open. Dumping hot coolant when it's -15*F really makes a huge steam cloud. :} I gave up since then and converted to the "open" style.

Another Renix Traitor!:twak:



:laugh3:

Winterbeater,

You have a point. In my case I ran my 87 Renix with a new bottle for about 3 years almost from the day I bought it, with no bottle problem. It had a 160 T-Stat, and the 3 year old bottle failed because the shelf was mounted too close to the hood, before I learned of that problem and the fix for it.

Since then I have had more frequent issues, but only recently, and the first new issue, (other than the hood proximity to the bottle shelf, which I still need to fix), was the bottle cap, which was permanently solved with a simple worm gear clamp. I did not have the lower nipple failure in 4 years on the prior bottle (87 jeep), only on the recent 1 year old bottle on the 89 jeep, which was the first problem with that bottle.

Meanwhile I have been fighting gremlins in my 85 Jeep open system since 2002, that still plague me today. But it is a hybrid, Nissan diesel stuck in what was once a gasser jeep. What acted like a head gasket leak, but it was not, turned out to be a backwards leak at the water pump shaft seal and WP gasket. Never leaked coolant (not in 7 years), just kept accumulating air at odd intervals in the system, never leaked coolant, but also refused to suck coolant back into the radiator from the overflow bottle. Still battling the return flow problem to some extent. Fixed the accumulating air problem, after 6 years of head scratching.

So I can't really say I have a preference for either system, when they miss behave!:twak: My open system has been more of a pain historically, until recently.

That said, I am currently looking at this as a research project of sorts. Not as a hurry up and fix it, be done with it thing. After all research is what I prefer (love) to do with my time, especially when I get paid for it.

Also, many newer cars are now using the closed system. They just have better bottles, like my son's Ford Taurus, 1996.

 

[Harlee&Tahoe]

I prefer the idea of closed sys to open due to the fact I run dusty trails and open systems are open to contaminants.
A solid bottle(aluminum w/sight glass) and copper lines with a back flush T like (5-90) has made looks to be the best possible.

I rarely run over 210* @100* going <5mph

 

[RTFM]

EcoMike, as I said in my thread I started and you replied to, THANK YOU for this thread and your work. :05of5:

Before I go off the deep end and jump to an open system, I'll preform your worm clamp fix.

Relocate my bottle mount lower (I think I have rubbing issues) and see how it goes. Although if I do rub I may already have stress cracks on the bottom of the tank, if then, it's off to Mac's for the aluminum bottle.......

 

[lawsoncl]

I prefer the idea of closed sys to open due to the fact I run dusty trails and open systems are open to contaminants.
A solid bottle(aluminum w/sight glass) and copper lines with a back flush T like (5-90) has made looks to be the best possible.

I rarely run over 210* @100* going <5mph

The "closed" system isn't truly closed as it does breath in-out of the cap on the surge tank. I think you still get dirt in the closed setup, its just that it gets mixed up in the system more than the open where it just sits in the overflow bottle. But yeah, it might collect less crap than the overflow bottle on an "open" setup.

 

[Ecomike]

The "closed" system isn't truly closed as it does breath in-out of the cap on the surge tank. I think you still get dirt in the closed setup, its just that it gets mixed up in the system more than the open where it just sits in the overflow bottle. But yeah, it might collect less crap than the overflow bottle on an "open" setup.

I agree, but I would like to point out that the closed system coolant never leaves the closed part of the system (until it Pukes anyway!:scared.

And the closed system, from my recent pressure tests, never breaths through the cap, as far as I can tell, until it hits maybe 240 F or higher, and maybe 32 F or lower. The trapped air in the bottle seems to compress, or expand to minimize pressure rises, and drops inside the system during thermal cycling, unlike liquid in an open system.

 

[Muad'Dib]

Ok, today i made it down to the hardware store (Happens to be an Ace Hardware) and found something perfect for the bottom nipple for the tank.

Its a 3/8" x 2-1/2" brass nipple. It was highway robbery @ 5.99 .. but it does work. You will probably find it cheaper somewhere else.

It threads into the bottom nipple fairly tightly... but it does go:

2-1/2" length works great. After you get it as far as you can into the bottom nipple, you just about have the threaded section left over. Its also the perfect amount of material for your pipe wrench or vise grips like what i used:

Now at this point you may be able to get away with leaving the excess alone unless you purchased a larger brass nipple. However, i wanted the excess cut off so i just busted out my dremel and cut off the excess. Afterwards i cleaned up the cut end's edge just by "shaving" over it with the dremel again (the cutting blade perpendicular to the pipe). This helped even up the cut and make it fairly smooth so it wouldnt cut through anything (it probably wont ever touch hose anyway.. just safe insurance).

There you have it... no more collapsing bottom nipple!

 

[Ecomike]

Great work, great pictures, a thousand thanks, :clap: as I just did a used POS swap for a used POS swap on the one where that nipple and the hose refused to seal. Still waiting on the 3 new bottles, so I will dig up some 3/8" nipples tomorrow for sure. Brass is definately the way to go, although steel probably would outlast these bottles even when it rusted!

Great work sir!arty:

Question, did you try any lube on it?

 

[Muad'Dib]

Nope .. didn't try any lube. Lube might have worked... it was definetely hot after threading the pipe in there. Either way its still a pretty tight fit.. but at least you know it isnt going anywhere once its in...

 

[winterbeater]

EcoMike, as I said in my thread I started and you replied to, THANK YOU for this thread and your work. :05of5:

Before I go off the deep end and jump to an open system, I'll preform your worm clamp fix.

Relocate my bottle mount lower (I think I have rubbing issues) and see how it goes. Although if I do rub I may already have stress cracks on the bottom of the tank, if then, it's off to Mac's for the aluminum bottle.......

Going off the deep end is continuing to work on your "closed" system. EcoMike is doing it more as a challenge and he likes to flagellate himself. (No offense intended.) I admire him for pursuing this challenge. By the time you mess with all of the bottle modifications and replacements, as well as the heater valve issues, you could have paid for and installed an "open" radiator with upgraded capacity and rehosed your heater core to run all the time. :soapbox:

 

[Muad'Dib]

Im a closed system advocate also.. IMO its far superior than the open style. This is of course considering that you have a good running system.

I think the biggest things that shy everyone away is the initial cost to get all the little kinks worked out of the 19-22 year old system. Yes the big downside is the darn pressure bottle... but if you pick up a quality dorman one, and do the trick to the bottom nipple and cap.. it should last you for many years at 1/4 the cost of an aluminum one.

 

[RTFM]

Well I don't know if it's karma or what - but went out to eat last night and the bottom of my 1 1/2 year old tank (unknown MFG) split.

It was lake XJ at the Thai place....... so it looks like I'm passing by the worm drive clamp and going to go directly to the alu tank.....

Although I am entertaining the idea of a newer XJ, as the '89 does have 303,000 miles on it now.

I'm just at that decision stage, replace or keep rebuilding to keep it going. As the only issue I have now is the cooling / temp problems. The rest of the rig is fine..... (starting to talk my self out of the trade to new as I type......)