kidkodiak

I only found two old threads about this, but since I'm doing a pretty major (at least I think it's major) cooling system fix next weekend, I wanted to make sure I understood how to do this part of it correctly, since air pockets seem to be troublesome for closed systems and heat fluctuations.

I read a thread where Blue said this about burping a renix system:

So Renix folks... here are my (probably stupidly simple) questions:

1. To my experience, since you can only fill the overflow tank with coolant, you'd fill here... but the fluid won't drain into the system from the tank until the engine is running. So... I burp it with the engine running, but how do I get enough fluid into the system the first time I start it up? Do I leave the cap off the overflow tank and just pour premixed fluid into it until it stops sucking it down?

2. if I have the overflow cap off AND the sensor is pulled off, am I going to be spewing antifreeze all over while I'm doing this? Probably a silly question, but I've never had to burp this engine, I always had a better mechanic than I do it

3. Correct my thinking... here's what I read when I read this:

-- with your cooling system drained and put back together, and the coolant sensor removed, fill the overflow tank leaving the cap off. Start the engine, and as the fluid gets sucked into the engine, keep adding fluid to the overflow tank until it stops taking more... then wait for the engine to reach temperature so that the thermostat opens and pulls more fluid.

Keep refilling the overflow tank until it stops draining with the engine at full running temperature, then kill the engine, put the coolant sensor back on, and fill the overflow tank to the recommended fill line. Reseal and voila! you're done.

Is this correct?

Thanks so much for the help

kidkodiak

Can anyone help?

BuckB91XJ

Remove upper radiator hose from radiator, over on the passenger side. Fill with water from there. Might be a little messy but, the Renix guys all claim tis is the best way to burp out all of the air

kidkodiak

ok, sweet that helps me out a lot. Thanks Buck!

5-90

Remove Thermostat.

Drill two small holes (1/16" or so) in the flange on either side of the poppet valve 180* apart.

Install thermostat with one hole at 12:00 and the other at 6:00

Stop worrying - the system will now purge itself of air. The air behind the thermostat will escape the 12:00 hole (displaced by water through the 6:00 hole) and will travel up the heater hose at the thermostat housing until it gets to the volume tank. Problem solved!

(Yah, I've been doing it this way for about ten years. Haven't had any trouble yet...)

kidkodiak

Thanks 5-90! But a dumb question, if you don't mind... how does the air purge, but the fluid not, in that scenario? Wouldn't the pressurized system force the fluid out said holes after the air is finished escaping?

I'm not very knowledgeable about the closed cooling system, so forgive me if that's a dumb question

nw-xj-scott

on my first 89' renix, i put in a 3 core rad, and just filled the bottle as it ran, kept filling it till it wouldnt take anymore. then let it idle for 20-30 mins on flat ground. with the cap off. i drove it for 6 months after that.. never had an overheating issue again..

my current 89' has been converted to open cooling.

1989cherokee

Do you need to burp it every once and a while or just when you change the radiator?

nw-xj-scott

you should never have to do anything but a flush every 30k.

kidkodiak

I'm thinking of doing the conversion to open cooling, but aren't quite ready yet. I might try the 3-core rad though if my current cooling fixes don't cut it

Thanks though, if I chicken out of drilling the thermostat housing, I'll do it that way

bharleyh

If this is not too late DO NOT drill holes in the thermostat housing. The previous poster was refering to the thermostat itself, not the housing.

fantic238

2X

fantic238

Here is a picture of a therm. valve, i've marked the hole spots in purple.

5-90

Once the system has purged the air into the volume tank, it's full of liquid. Liquid don't compress.

You'll always have a trace of flow through the thermostat (even with the popped shut,) but it's not enough to cause any real problem - and there's a bypass cast into the head anyhow (if you look when you put the thermostat into its counterbore, you'll see a little half-round shape off to one side that is open. It's just somewhere below the poppet valve...)

The advantage of doing this is that if you happen to get gas in your cooling system (air/fuel mix from a compression leak, steam void from overheating, ...) the system will automatically purge it as well - you'll still know something is wrong (if you pay attention to your gages,) but it won't be as crippling as it could be.

kidkodiak

Man, ya'll are awesome here. Thanks everyone for contributing. Takes a lot of stress off me trying something new when I can get so many guys who've done it who can help out

This place rocks =)