ramblinguy

Hello, I just bought a 1990 Cherokee, 4.0, auto, 4x4. It was a barn find, in nice shape, but not without some issues. Anyway, found several wires and such I need to know where they should go, or what they're called so I can connect them or replace them. I'm also having an overheating issue if anyone could shine some light on that. Replaced the thermostat and the temp sending unit, no luck. Gauge runs up almost pegged pretty quick . . . Anyway, see pic for the first "What the heck is this?" In the pic, the electrical connection is just below the lower left corner of the yellow sticker on the firewall . . . see pic.

In advance, many, many thanks !!!

Randy

lawsoncl

I'm guessing that's the connector for the underhood light that you don't have. Which temp sensor did you replace? The one at the back of the head by the firewall is the one for the dash guage. I assume you reconnected those unconnected lines to the heater I see in the picture and the surge tank? You might need to loosen the temp sensor at the back of the head to get the air out of the system - or drill the 3/16" hole in the thermostat that 5-90 recommends.

ramblinguy

Lawson, thank you! It was the under the hood light. I looked everywhere but up, ha! I did replace the sensor by the firewall, for the gauge. Ok, unconnected lines to the heater and the surge tank. I'm not sure what you mean by these. Can you help? Again, much appreciation! - Randy

ramblinguy

Oh, coolant surge tank? I put a new one one, but my luck, it leaks, so ordered another one.

lawsoncl

Yeah, the new surge tanks are pretty poor quality, and I found the bottle flexes, causing the caps to leak and cause overheating by not holding pressure. A few people have used a different Volvo surge tank that has thicker walls - I don't recall what model it came from. Personally, when my surge tank exploded, I swapped to the later "open" radiator that has a cap and eliminates the pressurized surge tank and added an overflow reservoir. It was for a 1992 I think. You can also eliminate the heater control valve that like to crumble and leak and just plumb directly to the heater core..

Good read:
https://www.naxja.org/forum/showthread.php?t=1094796

ramblinguy

I think that's the thing to do. What parts did you get off the 92 to make it work? What did you mean about drilling into the thermostat?

ramblinguy

Ok, decisions, decisions. I like that aluminum surge tank, easier I suppose than converting the entire system . . . But on the other hand I think an open system is simply a better set up . . .

lawsoncl

My radiator was plugged up, so I bought a new 1992 radiator that had a radiator cap. I plumbed the heater core direct, eliminating the surge tank and heater control valve, and capped off the vac line to that valve. You can use the heater hoses for a 1997+ to plumb directly to the heater core, as they eliminated that valve in 97. I grabbed a overflow tank off something at the junkyard and mounted it where the surge tank used to be. I don't even remember what it was from, and ran a 1/4" line from the radiator cap to the bottle. You can get a new generic bottle for $15 from autozone. Trans cooler fittings are the same, so no issue there.

http://mikestrawbridge.com/blog/2019...p-cherokee-xj/ gives the heater hose part numbers as Gates 19038 and 19039

On the thermostat, some have a small bleed hole to help get the air purged. If it doesn't, you can drill a small hole near the top. It's not critical, just help get the air out after refilling. Some more info: https://www.naxja.org/forum/showthread.php?t=939188

If you haven't already found them, there are lots of good tips on the older Renix era Cherokees at http://cruiser54.com/.

ajpulley

A quality expansion tank and a Volvo cap is sufficient. My ‘87 has ran this way it’s entire life without any issues.

Really, there is nothing wrong with closed systems. They are still used today by manufacturers of some models.

ramblinguy

Thank you so much for your help! Do you know to what this connects to?

Randy

dave1123

It's an overpressure blowoff which on an open system goes to an external reservoir. You could do the same to capture and return anything that comes out.