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New Renix Coolant Bottle and Cap problems

Inspected the Valvo cap and Renix bottle this week and noticed small stress cracks starting to show in both. Time to schedule a new bottle and cap finally. Still holding up fine in the summer heat so far.
 
Been almost a year and the heat is on here, and yet both Renix Coolant pressure bottles and Volvo caps I modified (bottle) and used(cap) in this aging thread have held up for another year and look like they may survive this entire summer again.
 
Did you ever get an answer to this black volvo cap versus green volvo cap question on the volvo caps?

My 87, while it has had limited use the last 3 years while I was layed up ill several times (not driving it), has made it 8-9 years now, and the other 89 jeep got totaled (rolled on the freeway :-( ) late last year but its modified bottle-green volvo cap held up fine. I am replacing the 87, 8-9 year old one now on my wagoneer.

But my re-read here has me wondering if the black volvo cap(?) was a real option? I thought the green cap was 16 psi? But now I am wondering.

My 8-9 year old one is showing stress cracks in the cap itself now and the bottle has stress cracks, deep enough to convince me I should replace it now. I am also replacing the bottle and cap and all the heater hoses on my new to me 87 white 4x4 I bought 4 years ago, and I am getting it ready for DD service so I can work on the 87 wagoneer engine/head, lifters etc... with out being in a rush.

I have been through this entire thread. Is there any hard data for system pressure when the vehicle is in use?

I went with the Volvo bottle and cap, twice. The first go-round, I picked a junkyard bottle with a green cap. After two years of thermal cycles, the bottle deformed enough to leak. This time, I incorporated the steel bracket used to mount the Volvo bottles. With the black cap, everything "looks" OK. With the green cap, the bottle looks bloated at the ends.

The reason for asking is that the black and green caps are rated approximately 11 PSI and 22 PSI respectively. I was told the RENIX cap relieves pressure at 14 PSI (Can anyone confirm this?).

More than anything else, I am concerned about over pressuring my heater core.

My bastardized mounting system.

STUFF006.jpg
 
Well Hypoid it is 22 psi, or about 21.7, as it is listed as a 150 kpa cap. The black volvo cap is only 75 kpa. I wonder if they make a 100 or 125 kpa cap?????

But I would rather err on the side of the 150 kpa cap I think, as the 75 kpa, black cap is only about 11 psi, which at best is about a 254 F boiling point with a 50/50 coolant water mix, but 22 psi is almost 30 F higher boiling point. Since air in the bottle is compressible, I do not think the higher pressure cap will hurt anything Renix bottle wise, and might save a boil over in extreme conditions like a fan failure or.... ? IIRC my Renix system topped out at about 8 psi on a gauge test I did once because of the compress-ability of the water vapor/air gas mix in the top of the coolant bottle on the closed Renix system. This is evident when you squeeze an open system hose at 16 psi and an closed system Renix hose with both at say 210 F. The Renix hose can be easily squeezed, the Open system can not be when they are operating temp.

What is interesting though is the open HO system reaches the high coolant system operating pressures (at a lower temp) long before a Renix closed system does.

So does this mean the Renix system can get hotter than the HO system under equal operating conditions since the HO reaches much higher operating pressures, at lower temps, long before a Renix would?????

IIRC the issue is keeping the coolant from boiling at the heat transfer surface in hot spots in the block, and not just the bulk coolant mix temp at the T-stat?

https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf
 
Just did some number crunching and the vapor pressure of pure water at 230 F (110 C) is 21.7 psi or 150 KPA!!!!! Bingo!!!! But that is for pure water, need to do sum of the partial pressure calcs for the net of a coolant-water mix...

OK too complex for posting here but 99% of the vapor pressure comes from the water, so 21.7 x 50 (50% water) is about 11 psi at 230 F. We hit the 260 F area for 50/50 mix at about 16 psi. And I recall some write ups saying the temps at the block wall-jacket wall can be way be higher than the bulk coolant at the T-Stat, so getting over about 240 F at the t-stat is I think where flash boiling in the block can happen, which is not a good thing. What does all this mean? To me it means it should not matter if I use a 22 lb Volvo cap as the system pressure will never get over about 10-11 lbs in normal use. And I never let mine get over 220 F, for any reason.

The vapor is what determines the coolant system system pressure in a closed coolant system like Renix!!!!! In the open system it operates at cap pressure almost immediately as it should have no gas in the system once the cap seals (water pump and some heat pushes coolant pressure at the cap above ambient).

http://www.kayelaby.npl.co.uk/chemistry/3_4/3_4_2.html
 
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Just did some number crunching and the vapor pressure of pure water at 230 F (110 C) is 21.7 psi or 150 KPA!!!!
http://www.kayelaby.npl.co.uk/chemistry/3_4/3_4_2.html

You're off a smidge (110C -> 143.7 kPa), but not much. Here's a handy lookup table too. https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf. Also consider that you need to stay a reasonable amount above that vapor pressure so you 're not cavitating in the pump which will eat up the impeller.

Personally, if you have to replace the radiator I would recommend using the radiator from a 92 and newer. I think that was the cutoff for the newer open setup that eliminates the stupid pressurized plastic bottle. Consider getting rid of the heater valve too, unless you're in a really hot locale.
 
The HO switch that eliminated the coolant bottle was in 1991. I was rounding off the 110 C, in a big rush, using tables and charts, not expected engineers with thermodynamics degrees to check my numbers to 20 decimal places, LMAO. In fact I may have copied that info LOL.

And I agree the pump cavitation problem is also a real issue...That is why I try to keep my from going no higher that 220 F (plus the bottles just are not built for steady use at higher temps).
 
Cap color on the Volvo cap does not tell the whole story. Autozone has the 150 Kpa (21.7 psi) cap with a black cap now instead of green with their part number 7033. It is stamped 150 Kpa, and the bottom valving looks different.

Looks and fits like the green cap I have used for 10 years. Time will tell
 
HOLY REVIVED THREADS, BATMAN!!!!!!!!!!!

12-15psi according to my 88 FSM. Confirmed.

I finally got a copy of the 1990 FSM: It says 12 to 16 PSI for a radiator mounted cap, 16 to 18 PSI for the bottle mounted cap.

I am pretty much done with the Volvo bottles. They are getting harder to find in the junkyard. I looked on line for a replacement and found them in the $50 range for a factory replacement. I was reading the specs when I realized the bottle is rated for the 11 to 12 PSI working pressure. Well derrrrrr! That is why they all have the 75 Kpa caps on them.

I still have spare bottles, and 150 Kpa caps, plenty of time to think about fitting another closed system reservoir.
 
That is interesting for sure.

"I finally got a copy of the 1990 FSM: It says 12 to 16 PSI for a radiator mounted cap, 16 to 18 PSI for the bottle mounted cap."

I guess they decided the lower pressure 1987 bottle cap was too low, LOL.
The bottle mounted cap has 3 sealing points, the 2 internal valves themselves (vent in and vent out) and the cap gasket that seals to the bottle. If we keep our rigs at or under about 225 F we really should not have any issues. My aftermarket POS plastic Renix bottle (modified as discussed here) on the 89 jeep outlasted the 1 year old aluminum plastic radiator (the upper passenger side plastic tank blew) by about 9 years and about 90,000 miles. I wonder if 21.7 PSI is too much for the cheap radiators? Both my 3 row all metal brass radiators are 8-9 years old now.

I suspect there are two different pressure rated Volvo bottles, but the higher pressure bottle may not be the nice fit of the one you have been using.
 
I'm still using the Quadratec bottle I got years ago. I bought a cap at my local Jeep dealer and it's held up well. I also have a new spare bottle as well as a Volvo one I picked at a JY (no cap).

I've been doing fairly regular flushes and check my coolant level often. My bypass valve is looking pretty ratty these days so I may have to splurge and replace it soon.
 
COOL, :eek: pun intended.

The reason for using the Volvo cap is the dealer cap is taller and the hood mashes the bottle-cap assy when you close the hood, unless you lower the shelf or use a low profile Volvo cap. I used 8muds worm gear clamp trick for some time on the aftermarket Renix cap, but did not like the crushed bottle stress cracks that were forming.

I'm still using the Quadratec bottle I got years ago. I bought a cap at my local Jeep dealer and it's held up well. I also have a new spare bottle as well as a Volvo one I picked at a JY (no cap).

I've been doing fairly regular flushes and check my coolant level often. My bypass valve is looking pretty ratty these days so I may have to splurge and replace it soon.
 
Yep! Mine is the "tall" cap. It's worn through the insulation under the hood. Yes, I stiil have it!!

I recall "bending" the bracket a bit downward.

IMG_0003_zpsvhz3tsin.jpg


IMG_0002_zpsbgqugx3f.jpg
 
Looks unused like its been in a museum LOL.
 
The bottles are the weak point.

I got tired of replacing them so I did an open conversion on my 3 Renix rigs. The radiators were almost new. Shoulda switch to the open style when I replaced them.
I'm planning on doing a write-up on it someday. I have the parts list done.
 
INDEED!!!!! You and I must be the only two that can get 8-10 years out of plastic Renix bottles on Renix closed coolant systems. At $25/bottle that is about $3/year cost, and most coolant hoses start to get questionable after 10 years anyway.

Funny, I checked the beginning of this thread and see my post from 2008. Yes, that's the same tank and cap.
 
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