'08 Dodge 1500 Ram with the 3.7 6cyl. 100K

Pretty regular maintenance kind of guy...started noticing that when I top off the radiator it blows a LARGE percentage back so I am constantly draining the reservoir with a little suction johnny and putting it BACK into the radiator which is low.. Sometimes I have even heard a 'voiling' noise when I stop after a long drive...

Check engine code came on. It was for plugs and coils. Took it in for a mechanic to look at.. Said I had a pinhole leak of coolant into the cylinder,..blown head gasket.
BUT used a BOTTLE OF k-seal and the little bit of white smoke went away, light went off. According to my Mech, if that happened THAT particular problem is solved 'for now' Long term, I plan on re-doing the head gasket... I would right now BUT>>>>>

. Car has been Great driving around town, but started overheating (or getting really close) BUT ONLY at HWY speeds?? Not turning on any lights, just uncomfortably close to the red line on the gauge

The Temp gauge has always sat just left of 12o'clock. Now that I have a 40-50 mile commute at around 70mph it start cruising uo to 2:30-3 o;clock. When I slow down back to 55-60mph it normalizes.

From reading this forum I Put in a new thermostat, and bought a new radiator cap. (both were indicated by stuff I read here)

Cools down faster BUT still getting too hot at 70mph. still blowing excess coolant back into reservoir.

TLDR. Truck Only overheating at HWY speeds, otherwise drives normal but keeps blowing coolant into overflow,

Thanks for any insights, info etc.

I think you are describing a coolant flow problem, likely a restriction caused by the head gasket sealant. You have enough flow to maintain temp at lower rpms, but flow is restricted at high rpm. I'd recommend replacing the radiator and a complete coolant flush. I'd blow the coolant out of the block with a shop vac to be sure I got it all.
The upper rad hose will be hot when engine is at operating temp. You have a 195 degree thermostat so the upper hose will be 200 degrees.
I suspect the head gasket sealant has clogged some of the fins in your rad. You may even find a clump of the sealant in the lower hose.

Thanks for answering. I am trying to figure this out. I don't mind spending money, but I do want to spend it on the right things. There' another post on this forum where guys had similar problems to mine and did a lot of 'laps'. (LOL) https://dodgeforum.com/forum/3rd-gen...way-speed.html

I learned something very peculiar about my Radiator on Sunday. After I bought the thermostat, and watched a 'how to' video, I took off the upper hose and there was no Thermostat housing! I found it in the 'lower' radiator hose??

So, all the remaining fluid came gushing out when I took that Lower guy off. My truck has that 'Transmission cooler' mini radiator as well, and I ASSume since the hose I pulled was below BOTH radiators , that for the most part it was 'drained'. After using the K-seal stuff I didn't notice any of those Juke ***** I used to see in old-fashioned 'radiator sealant' though I do realize they are not the same product. I was also a degree or two facing downward,(it was dark and I needed the light).....Wouldn't being downhill, pulling the Lower hose and then losing my fluid clean out most of that??? Or does it take force?
get to
When I was driving today (had to..work)... I noticed it's not the RPM's that trigger the heat as much as the HILLS and such. I was doing 72 on an easy straightaway at 2.2k rpms no problem, but going over the hill at 1.6k rpms made it get to 2 o'clock on my temp gauge fast...

I'm all ears

thanks for any info

You have the 3.7, which I've heard is same as the 4.7 with 2 less cylinders. Your stat' housing is where the lower radiator hose attaches to the engine.

Now when you say "blowing coolant back into reservoir," I'm thinking that's perfectly normal. The overflow tank is there for specifically that purpose. Now if the coolant isn't flowing back into the engine when it cools, then you need to check for either bad radiator cap, or leak.

If you're going to use some type of block seal (I've done it in the past and it's still working to this day)... don't use the stuff you pour into your coolant and leave there. My thinking is that eventually it will cause clogs, especially the heater core. I used the stuff that has you drain the coolant and add with water, which you run for a while. Eventually you end up with coolant again but once that stuff has dried. Worked great for me.

I don't Think it's flowing back into the engine when it cools....After I did the thermostat and ran the heater with the cap off for a long time (per an online video) to help chase air out of the system, I topped off the radiator and left the reservoir about halfway between low and full.. It was past full after my first hard drive..I did a big lap around town to see if it happened again..It did.

So, I replaced the radiator cap. Bought the lever vent guy. I have been working about 50 miles from home and am afraid of getting stuck on the road so I haven't driven it much since, but the one test drive I took , It is still doing the same thing.....fine at low speeds, getting waaay too close to the redline for my comfort on 70mph+ or hills. (about 3/4's of the way)

Mind, It always cools down quickly when I return to lower speeds.

This labor shortage affecting the country is REEEEALLY hitting us hard hard in Nashville, because everybody's been abandoning the coasts and moving here. I asked the local Mech who first looked at it when he could do my head gasket and he said "30-45 days out" and he was not kidding. Ouch. I am about to drive out and pick the brain of another mech today, but I am not sure about his availability either....thus making my appeal to the broader Dodge community... HEEEEEEeeeeeeelllllllpppppp. I am melting (LOL)

Coolant expands when it gets hot, and dumps some into the overflow reservoir, as the engine cools, it should draw it back in. If that's not happening, then you have a leak somewhere.

Overheating at freeway speeds is kinda odd..... There should be more than enough airflow thru the radiator to keep it cool. Might be interesting to take it out, drive it, get it nice and hot, then shoot the radiator in various places with a temp gun.... if you have cold spots in the radiator, that would imply its clogging up some. Flushing it may help, but, if it doesn't, time for a new radiator.

Is your head gasket actually blown? Are you losing coolant? Does the system pressurize as soon as you start the engine?

It doesn't draw it back in... I just came back from the parts stores where I got little hose clamps for the tube leading to the reservoir which was really loosely in place...I just came home so I will check it again when it cools down completely to see if it has taken any coolant back, BUT...
.
..at O'reilly's the guy thought I had an air bubble so we sat and 'burped' the system for a long time. There was a lot of air in there HOWEVER when I just road tested it I have the same problem about running to about 2:30 on the temp gauge, but cooling off quickly at street/slow hwy speeds.

Yes, I am getting full pressure, No, no coolant leaks. A wild guess might be that the K-seal blocked something near the block that only 'exposes itself' at high speed???

I had been blowing some white smoke pre-K-seal, but that is down to a whiff...but who knows what really happens down there? I am learning, but I am not THERE yet. (LOL)

thanks again for all of the input.

K-seal? That is likely a contributor to your problem. Get a cheap temp gun, check the radiator, engine hot. Bet it is partially clogged.

Air bleeding is done with the front end jacked high or up on ramps, heat temp set to hot. To check head gasket, start cold with radiator cap off. If the coolant shoots up, there you go. You can also rent a block tester.

I actually tried this today..It was hard to get a line of sight.... I think I am too SHORT to test that way (LOL)
I did park it on an incline and it 'burped' a lot faster than in the O'reilly's parking lot.

I THINK I have a mechanic lined up to do the head gasket. I described the 'blowing coolant out but not sucking it back in" thing. He pointed out that if the headgasket leak is by the cylinder the combustion would put reverse pressure on the cooling system....creating that phenomena

Thoughts? I wanted to do the head gasket anyways, knowing that the bottle thing is just a bandaid.... Like I said, I don't mind spending money...just want to make sure I am fixing the right thing.