I just purchased a 89 cherokee for my son from a dude down the street ($350.00), he had pulled the t-stat out, took the reservoir cap off, cause it would not tighten, put in a new radiator, new water pump and it still continually over heated. My knowledge of closed systems is not of the best, but for this system to keep the engine cool the coolant must be under constant pressure to operate properly correct? I reverse flushed the entire system, no restrictions, put on a new water pump, t-stat, and ordered the reservoir cap. Do you think the cap is the root of the problem? The new water pump I put in was just because I wanted to know.

First off welcome to CF,

When is it overheating? I.E. traffic, highway.

I would definetly get a new cap, that is the cheapest part to start with.

When it over heats, is it steady or spike all of a sudden?

Is your e fan working up to par? It is a one speed fan. You will be able to hear it when it comes on, it should come on when your a/c is turned on and when you temp hit 218 or so.

Have you tested your fan clutch? Does it spin freely when cold and not when its hot?

Does your lower rad. hose have an internal spring? This keeps it from collapsing.

Oh, does it have a stat in it now? if not you should put a 195 stat in.

lol i know this sounds nuts and i REALLY hope you did, but hows the oil?

just convert to an open system

x2

I plan to swap out the closed system to an open one when I have the cash to do so.

New oil and filter with total flush, valve cover gasket replacement to chech oil displacement through all lifter rods.

Thanks for your feed.