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(Suggest replacement Radiator) Pic of Radiator Overflow

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1990 started the interim years when crysler took over from AMC. This vehicle is most likely a still a renex system.

If that is the case, its does not have an overflow bottle, it has a pressure bottle on the pass side firewall. Its located up high, just under the hood. Its called a sealed system, there is no radiator cap, but the cap on the pressure bottle is similar.



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i noticed on my 88 there is no cap, i do have the jobber on the passenger side ill try to take a pic of it tomorrow and get it posted. Just a quick ques how do you add fluid if there is no cap. I havent looked but i didnt notice a cap on mine, and I was gonna flush the radiator and refill it..

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There is a cap, sorta, it's on the top of the pressure bottle.


For topping off the antifreeze, use that opening. If you're draining the entire system, many of us will pull the upper radiator hose off and fill the majority of the fluid through it. Except for me. I installed a later model radiator with a regular radiator cap stick out of the top. :D It's exactly the same as the older radiator, but has a small neck and radiator cap on it.


If you draining the system, another good tip for filling is, once you've put in as much as you can, prop up the back of the truck so the back of the engine is higher than the front (causing the bubbles in the block to congregate near the back, and then carefully unscrew the temp sensor (located at the top of the back of the head). Don't take it all the way off. Have someone fire up the engine (and be ready to shut it off if anything goes wrong), place a rag over the sensor to protect you if you unscrew it too much and it pops off (you are wearing gloves and safety glasses, yes?), and bleed the air out past the sensor threads. If you don't get all that air out, a pocket could form at the back and cause the engine to overheat.


It's the hexagonal cap in the pic.

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Here's the 88-90 4.0L coolant system bottle, from the Quadratec web site:






As noted, this is not an "overflow" bottle. It is an integral part of the pressurized cooling system. It will not function properly without a cap, and the cap has to maintain pressure. That's why it's generally useless to replace only the cap -- a new cap usually won't seal on an old bottle. Just buy the whole assembly.


It should not be filled all the way. It should be half full when the system is cold. NEVER remove the cap when the system is hot.

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You'll find pros and cons on both sides about swapping the closed to open systems. Here is a pic of an 89 that had been swapped to an open system.




The overflow is in the stock location of the later open systems and is the bottle that came with them. Kind of crazy seeing how the main power center is right there. I'll be changing this and going with a smaller bottle relocated in the bay. Haven't figured it out exactly yet and was thinking of putting one in the passenger side fender like I put the washer bottle in the drivers side fender. Just have to find the right donor for this mod.



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