98XJBlack

It is a 98 for sure. I am so confused now. They ran a pressure test and everything passed. He said the radiator, water pump, thermostat, heater core and hoses all looked good. I filled everything up with water last night and took a look at the coolant tank today and a lot of it is gone, but nothing has leaked out anywhere. It runs hot somedays and other days runs fine. The only conclusion at the shop was that air is trapped inside.

djb383

Have drained/refilled our '98 twice.....air in the system (burping) is a non-issue, at least on our '98. I'll bet the problem ain't solved. The rad may not be leaking but I bet it's clogged....don't see how u can have brown crud in the cooling system and it not be clogged. If flushing didn't work then the rad probably has internal scale build up and no flush job is going to work. How old is the fan clutch?

Wooddogg

Air in the system can and did overheat mine. The seller replaced the thermostat and it kept getting hot until my neighbor showed me how to get the air out.

I also just replaced the recovery bottle (it was old as heck), and squeezed the upper rad hose to force out the air into the bottle, she still running normal temps.

Good luck keepin her cool, Wooddogg.

djb383

........and your year model? U can't squeeze the upper rad hose on a '98 and force anything into the bottle.

blasterman93

Air pockets only if it is a sealed system which means it is an earlier model. I think pre 1993. Or did they go back to sealed systems later again. mine is a sealed system and i kinda like that considering there are no leaks to allow air to enter.

Wooddogg

It's an '89.

I learned that trick from the repair manual.

Bummer it wont work on a '98, thx & good luck, Wooddogg.

CAEMI

Enlighten me because I don't know how to get the air out of an open or closed system.

rich

Open system, do all your repairs etc top off rad and overflow bottle, start engine turn heat on full, let motor get to temp add coolent as needed. When it gets to temp, it should run out of filler neck (fluid) keep level at bottom of neck ,and when it stops gushing out you'll be all set, recheck fluid level and tighten new cap.

rich

Closed sytems I'm not totally sure so if someone else would chime in we would like to hear the proper way. If your not sure either than wait for someone that knows for sure. NO GUESSING lol

fantic238

Let me throw some light on the two systems.
In terms of cooling a close system is more efficient. The cap of a closed system is calibrated to open at 0.9 bar. This will raise the ebullioscopic point to 250 farenheit and allow the cooling system to keep working with temperatures above 212. This means that the total volume must include a portion of volume occupied by air that is necessary to allow expansion, and that is the expansion bottle.
The drawback is that the hoses, bottle, seals and radiator are subject to a higher pressure and will last less.
An open system, although open isn't really the correct term, it is still a closed system but the radiator cap is calibrated to open at 0.7 bar, the fluid will flow in the overflow tank and back to the radiator when the engine is cold, in this way you never have a portion of air in the closed circuit.
Since the overflow tank is open, some of the fluid will inevitably evaporate and get lost and operating temperature will need to stay under 230 farenheit.
In terms of purging there isn't any difference. Both systems when you fill them up, fluid will go to the engine through the lower radiator hose and air will come out from the thermostat housing.
When the air stays trapped in the block it is because the thermostat valve is completely closed and it doesn't have any holes to let the air go by.
There are many ways to purge the circuit, i've heard of people installing an aspirine on the thermostat opening or others unscrewing the temperature sensor to let the air out, but probably the easiest way is to drill a small hole on the thermostat valve and remove the upper hose to see when the water comes out while you are filling the circuit.

CAEMI

Interesting stuff...but how do I know if there is air in my system and if that air is actually causing a problem? I have a '94 with an open system. I have always thought that, because the overflow bottle is not airtight, that was the "vent" for excess air or air that results from minor boiling of fluid from hotspots.

djb383

Like I said in #17 burping a '98 is a non-issue, it burps its self as the engine goes thru its heat/cool cycles. The key is a properly functioning rad cap......it has a 2-way valve mechanism in the cap and both valves must work properly.

98XJBlack

This is all really interesting stuff to me. I think my problem is just an old clogged radiator. Even though it has been flushed I think to much gunk has built up over time. I am going to install a new radiator this weekend and hopefully this will solve my problem, heck it can't hurt at all. So here is my next question....Where and what radiator should I buy? Nothing crazy expensive, just a solid replacement. Thanks in advance!

CAEMI

I bought one at Advance Auto for $109. Seemed fine to me. Tell them the online price is lower than in-store and print out the online page...you'll save $30.

I know the high-dollar rad's are more better but for my use I could not justify $300 on a radiator. Hundred bucks got 'er done for me.

djb383

While you're doing the rad, replace the fan clutch as well. I believe the auto parts stores sell OEM style rad for +/-$100.