top reservoir hose pushes pressure out of it.

[greenchevy]

1989 Cherokee

This has a closed cooling system. I bleed the cooling system. When the jeep is running you can see and hear air and coolant being pushed out of the top little hose going back to the the reservoir. What is making it build up so much pressure?

[4.3LXJ]

Blue here is the Renix expert. But generally when you get a steady stream of bubbles like that it is because the head gasket is shot. The only cure is to replace it. Did it get real hot?

[greenchevy]

i dont get bubbles. With the system closed it pushes pressure out of the hose going back to the reservoir. I had a bad head gasket and changed it about a year back. It doesnt seem like a head gasket.

[default83]

probaly have crap in the radiator, causing it to back up instead of flow.

[greenchevy]

I'm thinking that's clogged to. When I took the cap of there was no water being pumped back in to the reservoir. I'm going to flush the cooling and replace the water pump.

[default83]

until you get around to doing all that, just drive the thing with the cap loose, that way no pressure builds up.

is the water pump giving you trouble? or are you just replacing it for peice of mind?

id pull the drain plug off and run water through the radiator for about 15 minutes see what comes out. also could be clogged up in the heater core, you might want to think about flushing that out too.

one more thing, replace the T-stat if you are doing the waterpump.

[greenchevy]

yea I'm replacing the water pump since I've replaced all the other cooling parts on this jeep. I've always had some type of cooling problem and never changed the water pump since I've had it. Also does anyone know the size of the pipe plug in the engine block to drain it is? 1989 jeep wagooner limited. I'm going to flush the whole cooling system. When i rebuilt the engine i never drain the block so i figure now is the best time since i already have a clog somewhere. thanks everyone for your help.

[greenchevy]

I replaced the water pump. It was gone with no return. I flushed the whole cooling system. I have flowing coolant again but still have to much pressure at the bottle. I'm completely lost at this point.

[ParadiseXJ]

Also does anyone know the size of the pipe plug in the engine block to drain it is?

The block plug is 5/16" (or dang close to it) square. I followed somebody's advice and ground down a 3/8 square socket drive to fit.

That tool now has a special place in my tool box, works for tranny ( 5 spd.) fill & drain too.