Open cooling conversion

Sorry if I have posted a thread that have been aksed before, but I have searched for two days and cant find the right thread.

I got an 90 mod XJ 4.0 aut. I want to convert to open cooling system.

What do I do?
What do I need?

If there is an old thread, please post a link to this.

One more time - why?

Consensus is that the "closed" system, properly maintained, is every bit as good as the "open" system, properly maintained.

A conversion is not necessary.

I'm not going to go into reasons why again, so check around for my posts on various cooling topics. I haven't written the FAQ yet, but I'm going to have the time to do it now...

5-90

Planoxj: Thanks, just what i where looking for...

5-90: I have have seen your posts about this subject, and my answear will be: Why not?

The open system is more what I'm used to. My radiator is dead, so I will have to replace it anyway. My XJ is only for offroad and I have problems with overheating.

Ah.

I'll still stand by my statement tho - properly maintained, the two are equal in efficiency.

In fact, I recently bought an 89 with the cooling system converted (done before I bought it,) and my 89 Limited (effectvely the same equipment) actually runs COOLER on the "closed" system.

It's not that I'm trying to shut anyone down - I just don't see a point in doing unnecessary work...

5-90

to each his own i guess...

5-90 said:

Ah.

I'll still stand by my statement tho - properly maintained, the two are equal in efficiency.

In fact, I recently bought an 89 with the cooling system converted (done before I bought it,) and my 89 Limited (effectvely the same equipment) actually runs COOLER on the "closed" system.

It's not that I'm trying to shut anyone down - I just don't see a point in doing unnecessary work...

5-90

Click to expand...

I have always respected your input. In fact I can think of several write ups of yours that have made projects on my jeep much easier. I trully have appreciated all of your input.

And I agree that the open and closed cooling system are both fine system and either one of them could provide a better job of cooling as long as all of the parts are in good working order.

However, the experience I went through when I converted mine was that first off the newer radiator was cheaper and to do the conversion (with all of the extra parts (thermostate housing, heater control valve, etc) was still like 20$ more than the older radiator.

What I do not like about the old system is the fact that I can not top up the radiator without letting it cool down!! The other thing I did not like was the burping procedure to the old system. The plastic bottle and cap I never trusted but I did not have any issues with them.

All in all I am much happier I converted. Both cooled my xj just fine, but I much prefer the newer system.

The one issue I still have not perfected with the new system is making the electric fan turn on with the GM temp switch that I used. I just can not get it wired right to make it work.

Michael

Sure you can! If you need to top off a hot radiator, you do so slowly with the engine running - this prevents the formation of "cold spots" that can cause you a lot of grief. This is the same way you're supposed to top off an "open" system.

The only thing that I do "different" with the closed system (which ain't that damn different, since it do it to everything) is the two 1/16" holes in the thermostat flange. It makes the closed system "self-burping," and can save you a lot of headache if you have a compression leak at the head gasket (on any system.)

A question I've posed elsewhere and often still stands - if the closed system sucks so much, why are OEM's moving toward it? My only complaint with it is that I would prefer a metal tank over a plastic one - but I'm cranky. It may seem silly in this age of "planned obsolescence," but one of my engineering principals is that you only have to buy a new part if you buy a new vehicle that doesn't have one, or if you manage to seriously bung up the first one somehow (which probably means you're more creative at destroying things than I am at designing them, and I'll probably want the old one back to see what I missed.)

Cranky? Mais oui! I'd sooner sell you something that I know will work than sell you the same part for the same vehicle over and over... Wait until I get a few more things designed...

5-90

5-90 said:

Ah.

I'll still stand by my statement tho - properly maintained, the two are equal in efficiency.

In fact, I recently bought an 89 with the cooling system converted (done before I bought it,) and my 89 Limited (effectvely the same equipment) actually runs COOLER on the "closed" system.

It's not that I'm trying to shut anyone down - I just don't see a point in doing unnecessary work...

5-90

Click to expand...

You may change you're tune if you're pressure bottle splits on a Sunday or the local dealer is out of stock on the bottle because the closed system will not cool properly if the bottle leaks. If you're replacing the radiator the other parts are cheap and it's cheap trail insurance.

2xtreme said:

However, the experience I went through when I converted mine was that first off the newer radiator was cheaper and to do the conversion (with all of the extra parts (thermostate housing, heater control valve, etc) was still like 20$ more than the older radiator.

Click to expand...

Why will you change the thermostate housing?

Is it to place the temp sensor there?
I'm planning to set up the sensor in the return hose.

slowrider said:

You may change you're tune if you're pressure bottle splits on a Sunday or the local dealer is out of stock on the bottle because the closed system will not cool properly if the bottle leaks.

Click to expand...

15 years.....225K + miles.....SAME bottle. New radiator, hoses, thermo, water pump....the bottle is just fine. It is like anything else, anything can fail at anytime....but the closed system is just as capable and reliable as the open.

Rev

Correct - the later housings are tapped (3/8" NPT, I think) to accept a temperature sensor. Since you will be eliminating the one in the radiator tank (which turns the fan on and off,) you will need to replace it somewhere.

You should be able to find a sensor that fits that thread without too much trouble - try to find one that turns the fan ON at around 215-217*F, and OFF around 190-195*F. There's a couple part numbers for Chevvy that should work, but I don't recall them offhand and I don't know if they'd mean anything in your market anyhow. If you can find a decent parts guy (a true rarity!) he should be able to find what you want if you tell him what you're looking for.

You'll have to adapt the wiring from the OEM RENIX thermal fan switch to fit the new sensor - I don't know what's available (again!) but tell your parts guy you need to adapt and he should be able to help you.

5-90

Well, I never trusted opening up the plastic cap to fill a hot radiator. Maybe that is my sensitivity rather than a problem with the system.

I do still prefer the cap on the radiator and the overflow tank that I can see and fill when hot. Again, just my preference.

I used the newer thermo housing to put the GM style temp switch in. I have it in, just can not get the wiring to work. One day I will do enough searching and playing to get it to work, the write up's I have ready were not easily understood. And it is hard to test since I can not get my jeep hot enough to turn it on often.

Michael

I did the conversion about a month ago, and it works great.

What I needed:
Generic coolant bottle from Advance Auto
GDI Radiator for 92+ cherokees
6 ft of 5/8 rad hose
6 ft of 1/4 fuel hose
Radiator cap
92+ Heater control valve
Total: $177

And that's it. Put it all in according to that walk through, and you should be golden. The new GDI radiator even comes with a threaded hole for the old style temp. sensor that goes to the fan.

Aluminium rad or not?