1987 Cherokee w/ inline six and that terrible closed loop coolant system (no radiator cap) and the coolant reservoir boils over and leaks. Bought a new reservoir, still leaks but only after driving it down the road. Can’t get it to leak while idling. No overheating at all, it was 105 outside when I drive it today for about 15 minutes and temp gauge never got over middle of the road. Coolant is green mixture without any signs of oil or anything. No knocking, no overheating, no stalling, just reservoir overflows and spills coolant all over the side of the engine and the exhaust manifold.

How do I even check the coolant level without a radiator cap? Could this be something other than a bad thermostat and/or water pump?

Not sure it’s related, but recently the ac stops blowing under acceleration, just stops blowing and then starts blowing again after we’re at cruising speed.

 

The "open" cooling systems on the earlier model XJs are a royal PITA. Next time you need a radiator, you'd be well served to replace it with a newer model. It just takes some new heater hoses; not a huge deal...

But anyway, back to your question. It sounds like you have air trapped in the engine. That's the biggest downfall of the "open" system, it doesn't self bleed... On the driver's side of the engine, at the very back of the head, right by the firewall, the Temp Sensor for the Gauge is threaded into the head. Park nose-down on a hill, or jack up the rear, and unthread that Temp Sensor just enough to let the air come out. Once fluid starts coming out, you're good to go, thread the Temp Sensor back in.

Regarding the AC, are you sure it's cutting out entirely and not just changing to defrost? Vacuum is reduced when accelerating, causing the various actuators not to work effectively if you have a leak.

 

Note from DJ

How full are you filling the bottle when it cold; there is a mark on the bottle that is marked minimum.

Is that where you filling it when it as cold?

 

Welcome to the wonderful world of Renix. If it's leaking from the cap, the cap's no longer any good. Doesn't matter what caused it. Replace the cap with a one from a volvo. I don't recall the part number but someone will.

It could be any of the above. Can you please clarify what you mean by spilling coolant on the exhaust manifold? The coolant bottle is on the other side.

My coolant bottle with the Volvo cap.