It Cannot Be This Simple?
bwp240 last edited by bwp240
Welcome back to the ongoing epic of restoring a 1989 Dodge Dakota convertible. Pulled from a barn and worked by human hands, this truck is now running. When we last left off, the truck was running and driving; stopping on the other hand, not so much. Pushing your foot to the floor resulted in creeping to a stop. It was unnerving, but manageable. Being prudent, brakes were ordered and we awaited their arrival.
At this point we have restored the truck to as advertised condition (minus the brakes). When I first purchased the truck, I knew that it suffered from an overheating issue. That’s what we are going to tackle today. The previous owner told me that his son was driving the truck and noticed it was running hot. Thankfully, they caught it before it overheated and burst anything. The cooling system on this truck is pretty simple. It consists of a radiator, water pump, thermostat, heater core, lines, and hoses. The previous owner stated that a new radiator was required.
Even though radiators are pretty cheap, I did not want to just start throwing parts at it (I am not made of money after all). Nope, let’s inspect the system and do some diagnosis. Popping the hood I noticed that the radiator was full and the fluid was green. I was told the water pump was replaced recently so there was nice fresh fluid in the cooling system. I also noticed the reservoir tank was empty, that’s a little strange. With those things noted, let’s verify the issue. I liked this because I get to drive the truck around. After a few minutes of driving, I noticed the temp gauge reaching past where it was supposed to be and increasing. It was not shooting up, but it was progressively getting warmer. I had the heater on full blast and was getting plenty of heat. Good news for my winter top down driving. I pulled the truck in and inspected the hoses.
Determining cooling problems is a hands on experience; however, don’t get too handsy or you might get burned (i.e. do not take the radiator cap off). Heat (and various other debris) coming through the vents verified the heater core and associated lines were functional; that’s good so I don’t have to take the dash apart (at least for that). Placing my hands on the top radiator hose and feeling the heat told me the thermostat is working. The bottom hose was warm, but cooler than the inlet which indicates the radiator appears to be functioning (perhaps clogged?). Feeling all the hoses around the water pump yielded much warmth and verification it was working.
To the best of my knowledge, the cooling system is working, but it is still overheating. Why? Now it was time to bring out the specialized tools. There were 3 more tests that needed to be done. Is the cap working? Is the cooling system pressurized? Are there combustion gases in the coolant? Thankfully, most auto parts stores have rental tools to diagnose just that.
(Editor’s note: The following occurred the next day when the engine was cool)
First test was to pressurize the system. The Dakota’s cooling system runs at 15 psi so pressuring the system to that should reveal any leaks. At 7psi a noticeable air bleed was coming from somewhere. That somewhere ended up being right at the top of the radiator hose where it connected to the radiator. “Great!” I thought, "the radiator must be cracked here and causing a loose connection." To be sure, I disconnected the hose and inspected it as well as the top of the radiator. Everything looked ship shape, there were no cracks, no nothing. Hmm, maybe the hose clamped isn’t tied down enough. After tightening it down and pressurizing the system, it held a constant 13-15 psi. That was easy. Too easy…
The pressure tester also comes with an adaptor to connect the cap. If the cap is defective, it won’t pressurize properly; thus overheating the engine. Pumped it up to 15 psi and there was no movement. The final test was the combustion gasses. This tool uses a sucker, a blue liquid which changes colors of combustion gasses are present, and a pump to sample the air in the cooling system. Starting the truck and letting it get up to operating temperature I could see that coolant was flowing through the system. Not rapidly, but moving nonetheless. Upon sampling the gases, the dye stayed blue. Good no head gasket issues.
Since the truck was up to operating temperature, I might as well see if it is still running hot. Replacing the radiator cap enabled the system to pressurize quickly, and… the temp gauge stayed at half. I was flabbergasted. Surely this whole cooling problem was not simply a loose hose. My friend said, “It sure looks like it, and don’t call me Shirley.”
MisterButtercup last edited by MisterButtercup
@bwp240 whoa, I'd say take that win and run with it!
...but yeah that seems suspiciously simple. Unless it's a "Son did you check that hose?" "Of course I did Dad, sheesh!"
Highlander last edited by
@bwp240 I thought my car had blown a head gasket, turned out to be a bad radiator cap. $10 part almost ruined a 2 week vacation.
Taylor Martin last edited by
@bwp240 Easy fixes are the best fixes. Seems you dodged a nice big bullet and save a whole lot of pennies on that one!
tysmagic last edited by
@bwp240 and this is why you don't just start throwing parts at things. Great discovery and seems like easy fix is the best fix here!
Darkbrador last edited by
@bwp240 Excellent detective work.
As for the my turn in the mandatory "I had the same story on my 19XX YYYY" :
1990s Ford Ranger, manual, 4x4. The owner had a hard time rowing his gears. The local and "reputable" shop diagnoses a bad gearbox, can source a used one for $2,500 + labor. The owner agrees to sell them the Ranger for $2,500. "Not so fast !" I say. Sure enough, the little reservoir for the hydraulic master cylinder was close to empty. It now shifts like new. That's it. For real.
So for MSP Oppos, don't go to the well-known shops whose name rhymes with "Mommy and Leaves"
rctothefuture last edited by
That's the problem with old cooling systems, if they aren't perfect then you get issues like these.
Nice job on the find though! If you plan on doing any more restoration down the road, Harbor Freight sells these kits for super cheap and I have all 3 tools on hand just for these instances.
LooseonExit last edited by
Nice detective work and not just parts canoning wildly.
Those plastic tanks do fracture though. Mine exploded in the driveway one day post-drive. Good thing my face wasn't under the hood... Yours sounds like it's fine now, but something else to check - my '93 had the tow package/HD cooling. This gives it an OEM external trans cooler that was unbeknownst to me leaking, gunking up only the front of the rad. No visible issues from under hood or the front of the vehicle. I think it lead to a hotspot and the death of the rad. Overall cooling temps were normal.
There might have been a leak...maybe.
Side note, decent upgrade if you don't have one from a junkyard. Thinking not too many of these are left, but might be worth your time. Also had an in-line PS cooler.
@misterbuttercup Mechanically inclined is not how I would describe the previous owner.
@darkbrador Yeah, pretty much the same story here. Their mechanic replaced the water pump; seemed to remedy the issue for a bit, then it came back. Their mechanic "diagnosed" it as the radiator and that's when they threw in the towel.
I am not 100% confident the issue is fixed (haven't had enough brakes to want to test it on a main road much less the highway), but on shorter drives and idling, it is keeping temperature fine.
MisterButtercup last edited by MisterButtercup
@bwp240 lol well that's awesome for you!
@looseonexit Hmm definitely something to look for. Although mine has the tow wiring, it did not have a hitch installed (outside of the bumper pull). That is a mod I am looking to do. I will have to look underneath again and see if it has a trans cooler. I don't think it does. I have to go to the junkyard anyway to get a washer fluid reservoir. Mine is cracked and all the fluid leaked away.
@misterbuttercup Indeed. As I dig deeper I keep finding odd mechanic "fixes"...
pip bip last edited by
@bwp240 that's a win
This is a great lesson on being able to see the big picture before making the call. Thanks for sharing before we all dive into our projects for the weekend.