How to Bleed the closed cooling systems

[mbogosia]

Can someone give me a step by step on how to bleed the closed coolant systems? I tried to search and can't get anything to come up. I have to replace a busted radiator tomorrow. I would upgrade to the open system, but I have a free closed system radiator. Or should I just drop the $110 and upgrade to an open radiator?

 

[winterbeater]

Open is not necessarily an upgrade.

Start by reading these: http://www.naxja.org/forum/search.php?searchid=3547992

One common theme is to drill holes in the thermostat to make it self bleeding.

 

[DesertRunner]

theres a thermostat sending unit at the back side of the block i believe its on the driver side almost against the firewall (single wire) loosen it as you fill the rad when coolant starts to come out there your good to go!

 

[mbogosia]

Winterbeater - I clicked your link and it said "sorry no matches"

DesertRunner - That is something I did not originally do. I just filled and it up and went. After a long drive there was so much pressure my radiator busted. Anyone else have some advice to get this right?

 

[cruiser54]

Park it nose down while filling and loosen the sender as suggested.

 

[winterbeater]

http://www.naxja.org/forum/search.php?searchid=3548745 Well, we'll try it again. Some say nose up, some say nose down, some say it doesn't matter.


OK, it seems to work now. I just put in "cooling system bleed" into "all forums". It is wierd how "technical forums" gives no results. But that's the way it usually works.

 

[mbogosia]

Well, I ended up buying a newer style radiator. Went to pull a part and grabbed the heater valve and hoses as well. Also got a overflow bottle. Hopefully I get this installed easily.

Winterbeater, still says no matches found when I click your link. LOL Oh well, thanks for trying though.

 

[AlabamaDan]

What about drilling holes in the thermostat? I don't understand what or how that works. Can somone elobrate? I did find a pic?

 

[kastein]

Doing that lets the water pump push/pull the air through the system more effectively - the air in the system will keep the thermostat from absorbing enough heat from the coolant to open quickly, drilling holes lets the air (and a little coolant) by so that the coolant warms the thermostat up, which opens it, letting the pump push the air through the system and self bleeding it.

 

[90 waggy]

ive found an OE t-stat from mopar and the sending unit trick do work. nose down. after let the jeep get up to temperature (still nose down) and leave the cap off the pressure bottle untill the t-stat opens....you will see bubbles in the bottle....fill to designated level and go have fun with it

 

[5-90]

What about drilling holes in the thermostat? I don't understand what or how that works. Can somone elobrate? I did find a pic?

I'll usually put them closer to the poppet valve (more in the centre,) but that pic is the right idea. Make the holes 1/16" to 1/8", and install at 12:00 and 6:00.

Why's it work? The upper hole passes air out of the engine and into the system, and it ends up in the plastic volume tank (replace that every five or six years - you can get replacements with caps from Morris 4x4 Center for a decent price.) The lower hole passes coolant into the block to displace the air.

Having the two holes helps to prevent "vapour lock" at the upper hole - this is supposed to be why the OEM units have a single hole with that little brass "wiggler" in it (to break up the air bubbles,) but I like the two-hole method better.

And winterbeater is correct - closed-to-open isn't necessarily an upgrade. The closed system can't be too bad - OEMs are using it more and more often.

Besides, out of the five RENIX XJs I've had, the one that ran the hottest was the one running an open system - and I was considering changing it back for a while. Properly maintained, there is nothing at all wrong with the closed system.

 

[Bdiddy11]

Drill thermostat like suggest, but as 5-90 said, closer to the poppet. You gotta have it closer so it's not drilled in the flange where it sits flush against the block, that would do no good.

Bleeding:

Park nose down (as suggested) I was able to jack the back up because I couldn't get somewhere with a hill to park nose down

There is a sender thing on the right side of the block (looking at it) right next to the firewall, it has a sensor thing on it. Remove it.

Get your socket set and loosen the bolt/screw, get it to where you can twist it with your fingers.

Fill up your coolant.

Once it no longer goes down from the bottle, SLOWLY finish unscrewing the sender piece and eventually coolant should come out of it.

You can make this a clean job by untwisting it slowly so the coolant doesn't come shooting out. I found it easiest to do on a cool engine so hot coolant wasn't getting on my hands.

I replaced my radiator on my 89 because it was old, and had a broken neck where the upper rad went in. With that, a new thermostat (drilled) new upper/lower rad hose and 2 row CSF radiator from Radiatorbarn + 'burping' the system as described I haven't had any issues with overheating and it stays quite cool.

 

[AlabamaDan]

:confused1 Amazing isn't it? We have to modify brand new parts for our XJs.

 

[Maltese Chief]

Open vs. Closed

Both of our audi's, 1996 and 2000, have closed systems. If Audi is using them on their high tech engines (V6 twin turbo) then the closed system must have some advantages.

 

[avnsteve]

the closed system is a fine way to cool a car, the problems come most often when people allow the radiator to clog, and then cannot add more coolant, or use common tap water usually with high mineral content causing the radiator to clog, or the weak expansion bottle bursts. those are weak links in an otherwise superior design. at least in my humble opinion

 

[veedubshafer]

Re: Open vs. Closed

Both of our audi's, 1996 and 2000, have closed systems. If Audi is using them on their high tech engines (V6 twin turbo) then the closed system must have some advantages.

Audi/VW have always had closed systems.

 

[JJacobs]

:confused1 Amazing isn't it? We have to modify brand new parts for our XJs.

No, you don't. It seems to be a popular thing to do here, but I've put in tons of thermostats in xj's and everything else. No holes- no problems.