The Dreaded Highway Breakdown

[Ron H]

Suppose it's inevitable to have a breakdown. Can't recall the last time, it's been a couple decades, excluding today, as my Dakota overheated and had to park along an interstate. It IS a bitch when it happens. And I'm pretty particular with maintenance and service so this hopefully shouldn't happen. My Dak overheated some weeks ago, then seemed fine driving it on errands. It was due for service anyway so asked the shop to look into the possible cause. Well they replaced the hoses and cap and said they ran it several times. All ahh good?

Today on my way to take a bunch of stuff to my kid's place 220 miles away...I made it 45 miles and noticed the temp gauge climbing to max and shut it down pulling off to the shoulder. Overflow tank was full up to top...steaming like nuts and too hot to play around much. Let it cool down enough to get to the next exit 2 miles away to park at a truck stop. The radiator took at least a gallon of water and noticed what appeared as a trickle of water on the lower left side of the radiator. WDF, all the trips around never a drop of coolant on the ground. So got it towed home after waiting over two hours for the tow. Sure woulda been nice to have had some signals before I loaded the truck up. Got it home ran it awhile and be damned the water level is still full up. Must be a pinhole taking a lot of pressure to leak; but nada a drop on the driveway!

 

[Slap Stick]

Which engine?
May be a head gasket or cracked head if its a 318/360. They are known for cracked heads.
May have a bad impeller on the pump.
And the shop didnt replace the thermostat.
It's losing water so its eaithe going kit an external leak, an internal leak or the overflow.

 

[Ron H]

Which engine?
May be a head gasket or cracked head if its a 318/360. They are known for cracked heads.
May have a bad impeller on the pump.
And the shop didnt replace the thermostat.
It's losing water so its eaithe going kit an external leak, an internal leak or the overflow.

It is the teen, no evidence of oil contamination (oil sure looks pure-recently changed) or wetness from exhaust. No indication of any coolant anywhere on the motor. Water pump area bone dry, no noises running it…thermo replace...good question as I'm not sure; thanks.

 

[Cranky]

Might show signs of coolant leaking into the offending cylinders by checking the center two plugs on both sides. If they look the same, pull out the rest and see what they look like. If nothing looks any different you might try a pressure test of the coolant system if that shop didn't do it. When my 95 started over heating, it turned out to be a pin hole leak in the radiator and I got a few more years out of it by running a 7 psi cap I never have been one to run those 15-16 pounders......hoses seem to last longer too with the lower psi caps.....

 

[Ron H]

Might show signs of coolant leaking into the offending cylinders by checking the center two plugs on both sides. If they look the same, pull out the rest and see what they look like. If nothing looks any different you might try a pressure test of the coolant system if that shop didn't do it. When my 95 started over heating, it turned out to be a pin hole leak in the radiator and I got a few more years out of it by running a 7 psi cap I never have been one to run those 15-16 pounders......hoses seem to last longer too with the lower psi caps.....

Interesting - it's a 16lb cap...and geez I ran it around town for errands several times to full op temp after service with no ills...nada a drip on the driveway...until my first attempt running it 40 miles on the interstate...

 

[cosgig]

Sounds like a head gasket to me. Our Subaru did the same thing, around town, no problem. Get out on the interstate, shot up to hot hot hot! It was the head gasket.

 

[Builderguy]

When I want to check for a leak I use this type of product:

https://www.napaonline.com/en/p/BK_...kzY4Ch2v3QwYEAQYASABEgJQu_D_BwE&gclsrc=aw.ds&

Or you can get a loner test kit from O'reilly's (or similar) and just pay for the leak test chemical. This stuff actually works.
Easy way to find out if the head gasket is blown.

 

[Ron H]

will have to try that. Odd hey, ran the motor for 30 minutes ran to its normal op temp and no overheat no indication of any leaking...except I'd think putting a hand on the radiator cap by then should be hot-hot; but barely warm. Could it be as simple as a stuck thermo? Interesting inquiry Slap...

 

[Don Frelier]

A stuck thermostat would likely overheat in about 10 minutes.

 

[Slap Stick]

A stat can stick and unstick. Ant they can stick part way open. But this sounds like my old 92 2.5 Spirit.
Around town it was okay. Get on the highway and the gauge would go to the top of the normal range. Turned out to be a bad head gasket.
If an external leak it could be in a hidden spot and it leaks slow enough for the coolant to evaporate.
If it is a head gasket its a good time to do the plenum gasket and timing chain. Maybe even an oil pump drive gear and bushing.

 

[Triplegreen500]

My Daytona (1991, 2.5 turbo) overheated on me earlier this year, out of the blue. Fan relay was bad. Just as a thing to check.

Headgasket is fairly easy to locate. Pull the rad cap off, cold, and start and idle. Watch coolant flow. If theres bubbles when the thermostat opens ....headgasket. Normal flow is all fluid.

 

[Slap Stick]

In so believe his Dak has an engine driven fan. Mine is.
Bring it to operating temp and shut down. Listen around the rad and overflow. If bad gasket you shod hear the compression bubbling out.

 

[Tony Tee]

My 2000 Dakota 4.7 has almost 300k on the clock. Original owner. Had replaced the radiator 3 times .waterpump once thermostat a few times.radiator caps And a bunch of hoses. but the best thing I ever did for my cooling system was to buy the thickest core radiator I could find and install a 185° thermostat. It runs cool even when I'm stuck in traffic in downtown Miami in summer.

 

[moparedtn]

Eerily similar to a situation I experienced with the 5.0 Mustang back in the mid 90's.
Car would be fine until you took it down the highway for a while (it had about 175k miles then).
Once on the highway, temps would creep up to the "oh ****" point and I'd have to bail....
I changed out most all of the cooling system (and I mean ALL of it), to no avail.

Finally got fed up after one Sunday outing with everyone in tow....
Ran it up and down the road in front of the house until it was breathing heavy, then left it parked
and idling in the driveway and told it to do whatever it was gonna do, I was done with it.
Yep, did the whole Christine "SHOW ME" thing to the car.

About 5 minutes later, there came the white smoke out the left tailpipe...
Well hello, Mr. Head Gasket!

 

[Ron H]

Thanks much gents for your info - given me things to check on. I had been through bad head gaskets before; seems as though it included loopy engine idling and surging I don't detect here...suppose it could be where the fail is or I'm FOS.

 

[Darter6]

I had a LA engine that the thermostat fell apart. Drove fine around town. Out on the highway would overheat.
Opened it up and found 3 pieces.

 

[747mopar]

Thermostats seem to be getting worse for reliability, when I first finished my Charger it would start to overheat.. pull over, whack the thermostat housing a few times and it would go back to normal operation. Replaced it with a Mr Gasket brass thermostat, couple years later it stuck wide open. Easy way to remove it from the equation is just remove it altogether. With it removed it may not reach full operating temp but it won't stick closed and overheat either.

 

[Ron H]

Update: Today a friend having a radiator pressure tester came by and it passed the test. He's a veteran mechanic and I asked him to check the cap as it seemed to fit pretty loose. He agreed. I put the cap on from my '63 Plymouth and a much snugger fit (13lb vs the 16 on the truck) drove it 25 miles hard and later ran some errands...no overheat. Another bud wondered if the system wasn't actually fully filled with coolant after replacing the t-stat. It took a gallon or so of water yesterday and haven't lost a drop of it. Who knows? Maybe a combination of a bad cap and low fluid conjoined to have me parked helpless along the freeway...or simply the cap being da issue? If it IS great - but I'm spooked gawking at the temp gauge now, lol.

 

[Builderguy]

Any mechanic worth their weight should be able to get all the air out of the system after a thermostat change. But, then again, some techs are so full of hot air that they weigh a lot less than others.

 

[YY1]

Unfortunately the cooling system is one of the few weak points on the pre-4.7 era Dakotas.

However, they are relatively easy to work on.

I'm on my 3rd radiator, 6th water pump, countless idler pulleys, and refuse to dig my bad heater core out (requires partially removing dash)

Additionally, my overflow bottle (and washer reservoir) cracked, and I've had to change the two freeze plugs in the fronts of the heads.

On the positive side, that's almost the only work I've had to do to this 175,000 mile truck that gets used as a truck, and I mean as a truck.