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Overheating issues

GinisKratos

NAXJA Forum User
So i got a sweet deal on anoter XJ on craigslist. 88 4L Runs good, decent power, dana 44, towpackage for 300 bucks - I get it about 5 miles down the road and i blow the lower rad hose bursts... not a big deal its a 88 and original hose.

Fixed that - start it up, builds pressure and the little plastic deal that sends water to teh heater core blows... I had spare for that from when my 89 did that. No biggie. but now that i have replaced its STILL overheating. just not blowing water all over anymore. It builds pressure, what feels like too much compared to my 89.

Whats my issue? Im getting pressure in both upper and lower rad hoses. but its like the water isnt moving until i see the temp go up, i shut it off and losen the cap to releace some, i think i hyave narrowed it to one of 2 things. Thermostat or Water pump. Since i have never had these fail on any of my rigs im not 100% as to what it will do. especally on a RENIX engine. And with all the water that was going around in that engine bay i cant tell if the waterpump is leaking alittle to tell me it is goig out.

Thanks for the help in advance. Going to go out and take a look. Pull out hte Thermostat and toss it in a pan on the stove and see if it opens.
Ill check back in a bit. Thanks!

Ed
 
the pressure is controlled by the radiator cap but im not sure if its on that XJ as i heard older have closed system, newer have open system

when the pressure builds, the cap should maintain pressure at ~15psi by bypassing some coolant into the reservator.

thermostator or water pump do nothing with pressure, they all do is control how the fluid flows
 
In the closed systems its all ran though the bottle, the coolant flows though it always not just the over pressure. Its a pita for sure. Im going to flush the system jsut icase there are any blockages in there.

Also i noticed something diffrent from my 89, which the cooling in there works amazing. Is that in the 88 the coolent seems to be able to floow backwards though thte system. i can take off the upper rad hose. pour some water in it and see it come out the thermostat housing. In my 89 the upper rad house fills up and nothing comes out. Not sure if that helps. But its a lil more info :)

Ed
 
There should be no differences in the 89 and 88 stock cooling systems.

Are you running the stock closed system on your 89?
 
Coolant won't really start flowing until the thermostat opens--there is just a small bypass.

What concerns me is the hoses--do they feel really hard? The internal combustion engine makes one hell of an air pump when the headgasket is bad. Test the coolant for combustion gasses.
 
With my 87 I did what 5-90 suggests and drilling a small hole in the t-stat at the 12 and 6 o'clock position... kinda a self bleeder and helps the flow of coolant.

That seems to have helped my overheating immensely.
 
Yes the hoses are getting rock hard, i repalced the thermostat just because it looked like it could use it, tossed in some water fire'ed it up temp went up slow, pressure built up slow. was looking good... temp went to about 210 220ish

then POW! the coolant bottle cap shot off and i got covered in some really hot water... on my already sunburned neck lol... good times... Jeep has another dent and i havent even gotten it to the trails yet lol (it was the bottle and cap off my running Jeep, so i know it works fine)

I went ot NAPA and Schucks but neither have a Hydrometer (or whatever its called to measure the hydrocarbons in the coolant) Ill have to pick up where i left off tomorrow. Any other ideas? or things I should also check while im in there?

Ed
 
That overheated pretty fast. Faster than I would expect if it were just a matter of burping out the air pockets. I'm leaning towards bad head gasket myself. Got a leakdown tester to check for bubbles in the coolant?
 
yeah it took about 10 min from starting it to the time the coolant blew out. I do not have a leakdown tester no. Not sure what one looks like. At this point I was just going to assume or tihnk it is a fualty head gaskte and run from there. Everything else checks out.

But i do want to make 100% sure before i tear into it. would that tester work with a closed system like i have?
 
from my experience make surethe heater core is not clogged or bypassed wrong, and make sure the heater hoses going to the water punp and the other going to the tstat housing are not switched around. just my .00000000002 nonsense lol
 
Just made sure FireFly and they are exactally the same as waht routed on my 89. Im going to flush the system again and make sure things are good as far as clogs. Talked to a guy at Schucks and since i dont have white smoke comming out of the talepipe but its still building alot of pressure it could be a cracked block. Anyone conform that?
 
like stated before, it could be a lot of air in the system as well. its a pain to get it all out. after i replace fluid i let it run some with the coolant bottle cap off. then i let it cool some and 'bleed' air out of the temp sander on the back of the head.
 
Just made sure FireFly and they are exactally the same as waht routed on my 89. Im going to flush the system again and make sure things are good as far as clogs. Talked to a guy at Schucks and since i dont have white smoke comming out of the talepipe but its still building alot of pressure it could be a cracked block. Anyone conform that?

Not all bad headgaskets will give you white "smoke".
 
Ok so i am getting more white comming out the tailpipe then my buddies truck. Its alittle cold out so i was expecting some. but its lingering like it would when its snowing out. So there is somethign going on. At this point im thinking about just converting to an open system to get rid of alot of the issues with the closed system. So i can focus on if it really is a head gasket or not.

I took the thermostat out so i could flush the system just to be sure it wasnt a blockage, and the coolant isnt being drawn into the system like it should. (even before i removed the thermostat) it just sits in the bottle until i feel the hoses getting hard, alittle to hard and only starts sucking the coolant into the system when i losen the cap. WTF heh
 
You need to do a cylinder leak down or a compression test to see if any cylinders are leaking. The only short cut to this might be to pull the spark plugs to see if any look like they have been steam cleaned (by leaking coolant).
 
You don't necessarily need a true leakdown tester. Some of the compression testors have a quick connect on them so you can hook them up to an air hose. The idea is to put some pressure in the cylinders and look for bubbles or pressure building in the coolant lines.

I'd ask if the white smoke smells like coolant, but you said you refilled with water.
 
Yeah the lower rad house blew when i was driving it home so i jsut used water from there on. For whatever reason its not flowing though the system like it should. the water jsut sits inteh bottle while the pressure builds in the hoses... only when i releace the pressure does the water move. or so it seems by looking.

I did notice that when the bottle was over flowing there was bubbles comming from the upper hose that connects to the bottle, i reven the engine alittle and the bubbles got worse, and slowed again when i let off. So its definitally a head gasket. I have the replacment on order but it will be a few days.

I was hoping Blue Devil would work as a fix but it cant idle the 40 min without adding coolant (since the pressure builds tothe point where things start poping) so ill have to do the right way this time :)

Thanks for all the help guys. Ill keep ya posted.

Ed
 
Glass Seal might have been an alternative. You have to dump the coolant to do it, and you were already there. Glass seal is basically sodium silicate, which crystallizes in the potential leak and seals it as it dries. It won't dissolve later in anything.

Whether it would seal a moderate head gasket leak depends. You're probably doing the right thing changing it. Makes you wonder just exactly why the XJ was on Craigslist.

Changing to an open system involves a new radiator, heater valve, an coolant recovery tank, rerouting the heater hoses, and dropping the e-fan Thermal Fan Switch setup for something else the factory never designed. The '92 neck and Coolant Temp Sensor is not the correct answer - it works entirely wrong for a Renix. The open system changeover doesn't really cure anything but our unfamiliarity with the turtle tank - and some GM's have a cheaper, better design that's a common replacement around here.
 
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