Okay, the previous owner of my 94 Dakota was my brother, who was very lazy on maintenance. He would add water rather than coolant, and recently winter temperatures have been dipping below 30 degrees at night so naturally I wanted to put a new coolant rather than risk the garbage he had in the radiator freezing up on me.

So I drained the old fluid, which was barely green at all from being so diluted, I filled the radiator up and also the reservoir to the full mark. Replaced the caps on both and begin running my engine, with the heater going as well. After a few minutes I begin revving the motor, keeping it in between 1 and 2 RPMs.

After about a minute of this, I heard a sucking sound and I looked under the hood, the upper radiator hose was flattening out, similar to how a straw would flatten out if you were to suck on it while plugging the other end with your finger. I turn the engine off as quickly as I could as I had never encountered something like this. A gurgling sound could be heard coming from where the upper radiator hose connected to the radiator, but this stopped after a minute and the hose returned to normal

I'm unsure of the next step I should take. I have done this on a previous car I'd owned with no issues, and that was my first time doing it on my own.

For what it's worth, the amount of fluid I added was roughly the same as what had drained out - about a gallon and a half.

Your advice would be greatly appreciated!

Edit: I should add that the temperature gauge in my car didn't go past the center, between hot and cold. And right after the hose returned to its normal size it felt hot to the touch but not too hot. About 20 minutes or so after writing my post, I checked the car again and it had cooled down enough to remove the radiator cap without incident. The level had gone down about half an inch, and in the overflow reservoir it had gone down from the full mark nearly to the bottom.

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Sounds like the radiator cap is the wrong one for a Dakota.

There's a discussion of the various radiator cap designs at https://www.allpar.com/fix/engines/cooling-caps.html ; sounds like yours isn't a pressure/vacuum one. Or that it's stuck.

Could also be a bad thermostat; but I'd lay more odds on the radiator cap first (especially due to the age!)

But if that doesn't help, next step is the upper hose AND the thermostat (do both! Add the bypass hose while you've got the upper hose off ... )

(I'd highly recommend considering the lower hose and the two heater hoses also while you're in there; but that's not my money I'm spending there ... )

RwP

 

Prior to today, I've had no issues with the cooling system. No overheating, nothing. I believe the radiator cap was the one that came with the truck, the person my brother got the truck from was the original owner. They drove it from northern Oregon all the way down to Central California with no issues.

In fact, the only reason I changed out the fluid to begin with was because, as I mentioned above, the temperatures in the winter at night will be dipping below freezing soon, and with that badly diluted mix my brother had in the radiator I didn't want to risk take any chances.

 

You may be onto something with the radiator cap, I let my truck run for about 10 minutes and shut it off. I could hear a gurgling noise coming from the radiator cap. I checked with an auto parts store and they had two types, the standard Duralast one or one that came with a "safety lever", which is what my truck has. Which would you suggest?

 

Actually? Neither.

I'd actually recommend that the radiator cap is one part worth buying from a dealership.

Of course, that "dealership" may sell on Amazon or FleaBay instead ... *grins*

But if you must; I've not had good luck with the levervent style caps actually holding pressure. I'd opt for the DuraLast for now.

And if that doesn't help, time to plan on a hose replacement.

(And it may be that burping the air out may take care of it; might have been as simple as not enough to fill the cooling system entire!)

RwP

 

I know nothing about burping the system; from everything I've read both in this forum and elsewhere online there seems to be no general consensus on what exactly to do. I was thinking about adding more coolant into the Overflow Reservoir, wouldn't this push out any air that's left?

As it stands now I'm sort of scared to drive the truck until I have this figured out. I would take it to a shop but I don't get paid until the 1st.

 

To fill/burp the system. Turn on heat full blast. It needs to be on since the coolant is the heat source and being on it will flow through and drive air out of the heater core. Take off radiator cap (leave off til done) and fill it if it is low. Start the motor. let it warm up fully. Once the thermostat opens the water level will drop if the water in the system is low and the top hose will start to get warm from the coolant flowing out of the engine into the radiator. watch for air bubbles to escape. add coolant as needed. This takes a while, be patient. It will eventually stop burping. You can find videos on YT. Fill over flow to fill line
They make special funnels that let the coolant fill up into the funnel which makes it easier to see it burp and lets you remove it without spilling. I bought one and it does not work because it did not have a cap that would lock onto my Dakota rad. Of course I live where the people in business only sell crap so they can sell something else again later and so on.

 

sounds like you have air in the system.
when its cool, open the rad cap and see if its low. modern vehicles need to be vacuum filled. if you pour it in, air will be trapped and it will require thermocycling to remove the trapped air.

 

You want one of . It makes the job much easier, more effective, and less messy.

 

Got one of those from O'Reilly's and as I mentioned in my post it did not work because none of those caps worked on my radiator. I'm pretty sure I got the rad from Rock Auto. but its a normal top so why wouldn't there be anything but oddball connectors in that package? Not a single one of the tops that came with it was a normal radiator cap and the nipples have no way to tighten them in place once you insert them into the hole. The only thing that worked is the stick to plug the funnel. At least I got my money back.