Open cooling system

Right now I am staring at my jeep which has no front end. It is a 90 with a non HO. I would like to go with the newer radiator setup with the filler on the rad. I heard I need a heater valve? Anyone got any info I should know before doing this? It seems pretty straight forward. I'm gonna go with a rad from DPG, they have three rads for xj's; 88-90, 91-97 and 98 and up. I figure the 91-97 works even though its 20 bux more but the filler location is better placed I think. I'm gonna do the whole system up as I am slowly getting ready for a next summer's rebuild/stroker/lpg motor. Thanx y'all.

Blue_Blooded said:

Right now I am staring at my jeep which has no front end. It is a 90 with a non HO. I would like to go with the newer radiator setup with the filler on the rad. I heard I need a heater valve? Anyone got any info I should know before doing this? It seems pretty straight forward. I'm gonna go with a rad from DPG, they have three rads for xj's; 88-90, 91-97 and 98 and up. I figure the 91-97 works even though its 20 bux more but the filler location is better placed I think. I'm gonna do the whole system up as I am slowly getting ready for a next summer's rebuild/stroker/lpg motor. Thanx y'all.

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Some say you need to keep a heater valve in the system, others like me say you don't. I've converted three closed systems to the open; one time I used a heater valve, the other two I didn't. Some people say if you don't have one it makes your A/C work harder. I don't know whether that's true or not, but I converted one that had functional A/C and left out the valve; his A/C worked great before and after the conversion. If you opt not to keep the heater valve in the system you can replace all the heater hoses with about 4 feet of each size 5/8" and 3/4" bulk heater hose since you won't need all the bends the heater valve requires. This is only if you get the newer style elbow that screws into the water pump though, otherwise you will still need a 90* brass elbow or a molded hose. You can also order the heater hoses for a 97+ XJ if you go that route because they had already eliminated the valve in those years. Good luck with the conversion.
-Collin

I forgot to add any radiator from 91-01 should fit your 90. A lot of places list the same part number between those years.

Blue_Blooded said:

It seems pretty straight forward. I'm gonna go with a rad from DPG, they have three rads for xj's; 88-90, 91-97 and 98 and up.

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Unless they've changed the design on the radiator:

1. for the 88-90 there will not be a filler/cap neck.
2. for the 91-97 there will be a neck but not a hole for the aux. fan temp sensor.

My suggestion would be to get the 91-97, do away with the fan temp sensor and direct wire the fan to turn on when you need it. There are several write-ups on how to do this by just wiring it through the fan relay and putting a switch on your dash. As far as the heater valve goes you can either do away with it like 90Pio says or plumb it in just like a 91-97. I prefer having mine in because theoretically it makes it easier on the A/C in the summer. The valve may be prone to failure (it's plastic) but it's only $25 and easy to replace (I carry a spare).

i have an '89 on the closed system, what are the benefits of converting to the open system?

Thanx guys for all the info, I am the only one with the closed system so having one of my buddys rigs to look at won't be a problem. I also won't be running a/c due to I really don't run it at all even in my DD so I took it out of my jeep. I just need to get the bracket and idler for the total conversion. So basically just throw it in and not worry about the a/c, also I already have the aux fan wired on a switch so we are all ready for this conversion. Thanx for info guys.

TLowery04 said:

i have an '89 on the closed system, what are the benefits of converting to the open system?

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The only benifit is that you don't need to burp the system. Stay with the closed system.

and keep replacing that stupid ass closed system surge tank when it fails causing you to boil over....

outlander said:

and keep replacing that stupid ass closed system surge tank when it fails causing you to boil over....

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i've had to replace it twice now... and I've only owned it since june

TLowery04 said:

i've had to replace it twice now... and I've only owned it since june

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If the system is properly burped and maintained with quality parts the bottle will not blow........unless your headgasket is busted.

I had to replace mine 3x within two years. Well actually the third time I converted to the open setup and ditched the heater valve. The quality of those bottles sucks. iI it's the original radiator, it's probably plugged up by now anyway.

I rest my case.

Jess said:

If the system is properly burped and maintained with quality parts the bottle will not blow........unless your headgasket is busted.

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Youre a clown........ the bottles are weak and crack after warming and cooling. Also the cap is a weak point too, has nothing to do with head gaskets. A true "closed" system should be......... well "closed" not having a leaky cap to allow air (added air) into system.

Also remember while doing this swap you will not have the temp sensor switch you can swap out the thermostat housing for the 91+ and get a temp switch from a 80s corvette and wire the wires to it (go across the fuel rail for best access). Also with doing this swap the fan rarely comes on due to better cooling.

Jess is right to some extent, the closed system does work out just fine if it is maintained properly. However a cracked head gasket is not always what makes the bottles fail. My main problem with it is, you have to get underneath the Jeep to crack that damn CTS to burp the system. 5-90s method of drilling another bleeder hole in the thermostat does wonders for the self bleeding aspect of the closed system as well. Like I mentioned earlier, I've converted 3 XJs to the open system. I did this for 4 main reasons...

A. I like the cleaner hose routing, only needing two sections of heater hose.
B. The way I do it there's no heater valve to crack.
C. I had a ton of trouble with those "football" bottles, and no I didn't have a cracked head or bad headgasket. I bought the "reinforced" bottles with the "better" cap and they still didn't work for more than about a year.
D. I like the true self bleeding aspect of the open system.

And what I've started doing now is not running an overflow at all. I was looking at my Dad's '48 Packard one day and I realized in the older cars they just had a hose zip tied to the side of the radiator that ran the hose straight onto the ground. I know this is not environmentally friendly but I figure if the coolant gets to where it's going to expand that much anyway, it's going to "overflow" out of the bottle. My point with that being, it's one less thing to have in the engine bay. Just my take on the subject.
-Collin

90PioSport99 said:

Jess is right to some extent, the closed system does work out just fine if it is maintained properly. However a cracked head gasket is not always what makes the bottles fail. My main problem with it is, you have to get underneath the Jeep to crack that damn CTS to burp the system. 5-90s method of drilling another bleeder hole in the thermostat does wonders for the self bleeding aspect of the closed system as well. Like I mentioned earlier, I've converted 3 XJs to the open system. I did this for 4 main reasons...

A. I like the cleaner hose routing, only needing two sections of heater hose.
B. The way I do it there's no heater valve to crack.
C. I had a ton of trouble with those "football" bottles, and no I didn't have a cracked head or bad headgasket. I bought the "reinforced" bottles with the "better" cap and they still didn't work for more than about a year.
D. I like the true self bleeding aspect of the open system.

And what I've started doing now is not running an overflow at all. I was looking at my Dad's '48 Packard one day and I realized in the older cars they just had a hose zip tied to the side of the radiator that ran the hose straight onto the ground. I know this is not environmentally friendly but I figure if the coolant gets to where it's going to expand that much anyway, it's going to "overflow" out of the bottle. My point with that being, it's one less thing to have in the engine bay. Just my take on the subject.
-Collin

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I like yer thinken..

PornstaR said:

Youre a clown........ the bottles are weak and crack after warming and cooling. Also the cap is a weak point too, has nothing to do with head gaskets. A true "closed" system should be......... well "closed" not having a leaky cap to allow air (added air) into system.

Also remember while doing this swap you will not have the temp sensor switch you can swap out the thermostat housing for the 91+ and get a temp switch from a 80s corvette and wire the wires to it (go across the fuel rail for best access). Also with doing this swap the fan rarely comes on due to better cooling.

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The terms "closed" and "open" are not really correct. The cap on the "closed" plastic bottle is still a pressure cap just like the one you're used to seeing on an "open" system. It does lset air in and out of the system. It's just made out of plastic and failure prone.

Both setups are open to the air. The difference is that the fluid surge is kept within the pressured system on the "closed" setup, whereas the "open" setup lets it flow in/out of the system into an overflow bottle.

Well, I kept my closed system, turtle and all.

The turtle I've resigned to replacing annually, along with the cap. Cheap insurance at ~$25 from Quadratech.

For making burping easier, I did the thermostat hole thing, but I also used a newer-style thermostat housing that has the port for a sensor. Instead of a sensor there, I put a radiator petcock. Work's great for bleeding any air.

You can see it in the left of this picture:

is there a write up on this somewhere?

I am planning on doing this with my '89 as i beleive the original radiator is fouled and flush and back flush has not cured it.

I am converting the A/C into onboard Air and i put the fan on a switch along time ago because it didnt turn on when it was supposed to


thanks and i look forward to your response


Trent