[David Eidell]

'95 Dodge Spirit, started overheating 2-years ago. Verified gauge with IR scan thermocouple, runnning 225F+, never did before. Went through electric fan troubleshooting, replaced radiator, cap, upper and lower radiator hose, the radiator, the belts, the tensioner, the water pump, the works. Did not have benefit of PRESSURE TESTER PUMP which would have saved my butt down here.

The beneath the V6 manifold lower radiator hose transfer tube had a leak. Very small. It would force coolant out. Maybe a cup or so but no more than that in hot weather. Doesn't sound like much does it? The termperature gauge though differently. It would swing over to near "H". The coolant recovery system DOES NOT WORK if there is the tiniest leak in the system. I guess the vacuum is satisfied easier leaking backward through a small pinhole than it is by working against a radiator cap spring.

One LOUSY cup of water, that's all it took. It must have cavitated the pump's ability to suck water. When my aluminum engine heat gauge goes to near "H" it bothers me, a lot.

To top it off, not even genuine Alumaseal® helped the leak issue. It was tiny. it was more than tiny.

But never again am I going to get sucked into wasting many hours and a lot of money trying to outsmart a radiator pressure test gauge. I'm not foolish - the nearest one is maybe a thousand mile round trip and you can bet your burro I've got a Stant Pressure Tester on order, a twelve hundred mile round trip. The eystem will get tested to 15 lbs. If it loses pressure, if I see dampness then I'll get to work.

I've NEVER seen a motor vehicle with that level of sensitivity to a missing cup of water. Before you fume, read, what I have replaced. There are no "missing links". Until that pinprick size hole in the tube was brazed up the temperature acted as nuts as Norman Bates.

Maybe this bitter lesson can help someone else with a K car with 3.0 V6 engine.

 

[Bob Lincoln]

It is not lack of water, bur rather ingested air, which is making the gauge read so high. Once the air leak is fixed, and air bubbles purged from the system, it should stabilize.

 

[John Wood]

I think that the air being sucked in (as the engine cooled) and rose up to the thermostat, effectively insulating the thermo element from hot coolant. That keeps the T-stat from opening and that is why you overheat. The water pump is mid level and shouldn't get air in it unless the air ingestion was substantial.

The coolant tubes on that 3.0 have been known to rust through, especially on a system that hasn't had regular coolant changes. Dorman products sells aftermarket replacement tubes. It's not a fun project replacing those if your intake manifold, fuel rail, and injectors have to come off. Brazing a pinhole may work for a while until the next hole shows up due to corrosion.

 

[Dave Z]

Right, the first time I ever heard the term "bleed the radiator" was with the K-cars! A lot of people lost their heads, so to speak, from air in the system.

 

[David Eidell]

I went to the local "Caterpillar" dealer and ordered up some Nalcool 2000 anti corrosion additive. The problem has been fixed, the hole was primarly caused by a manufacturing defect. There was another area that was weak. An eighth inch of brass has solved that, But the real secret was a tool I could not lay my hands on. A pressure tester, Instead of coming out and evaporating only when the engine was hot, it would have leaked and shown up with a cold engine.

Nalcool is not the garbage additive, antifreeze manufacturers dump into their product. It actually works. A line haul tractor trailer operator would never put car antifreeze into their thirty thousand dollar engine and five thousand dollar cooling system.

I cannot believe manufacturers have gotten so cheap that a .1 (that's point - one) percent loss of coolant could fry the aluminum heads.

 

[valiant67]

Again, it is NOT the coolant loss that made it get hot. It was the air that got into the system. The air gets in and gets trapped against the thermostat. Air won't open the thermostat rapidly like warm water against it does. I had a similar issue with a Dodge Dakota that would randomly at idle peg the temp gauge then drop back as soon as the RPMs came up. Yet the coolant level was always OK. Ended up the hose clamp on the hose to the water pump was weak and at low RPMs it would suck in just a little air. Higher RPMs were OK and the air leak didn't stop the overflow tank from working to capture any coolant and return it to the engine.

 

[Rickorino]

Wouldn't a small hole drilled into the thermostat solve this issue?

 

[Bob Lincoln]

No, because it's still ingesting air at the leak. The leak has to be fixed first.

 

[David Eidell]

Wotta pain. The hole did not leave a clue. The hot engine evaporated any trace of coolant. It did not leak when cold. The tiniest bit of missing coolant made the temp go nuts. I'm never too old to learn, but please, spare the whips and chains! Aluminum block or heads overheating scares the $%# out of me. I've no doubt whatsoever the placement of the hole is the key to the severity of the symptoms. The intake for the water pump. OK, now I have an entire cooling system that will live longer than I will. Now I have to pardon myself and go wipe up yet another fresh round of tears from my wallet.

 

[dana44]

Wouldn't a small hole drilled into the thermostat solve this issue?

I always recommend an 1/8th inch hole in the face of the thermostat which will help a small amount of flow continue through the thermostat without affecting the warming of the engine, allowing air bubbles to purge all the time, not just when the engine is warmed up and thermostat open. In Bob's case though, an air leak because of a loose radiator hose will suck air because the cooling suction being greater than the radiator cap pressure to pull the fluid back into the radiator/engine when cooling may require force to pull air, so he is also correct.

Should say require less force to pull air into the system compared to the force necessary to pull past the radiator cap vacuum (when cooling), from the overflow.

 

[PCRMike]

Many of the Israeli made t-stats have a tiny ball valve in it to allow purge. Later v-6 engine (like the Jeep 3.7) have an allen plug in the top of the t-stat housing to purge the system.

 

[Bob Lincoln]

The 2.2/2.5 engines had this. I could never open any of them, even when new. Way too tight from the factory.

 

[chuzz]

I agree with Bob. I owned 7 of the 2.2 or 2.5's over the years and could never get that plug out of a single one of them. To the OP, check your heater hose clamps as well as your radiator clamps. If one of them is the least bit loose, it will suck air and drive you nuts trying to figure it out.

 

[B10alia]

Only gotten that damn hex plug open once to purge the system, and I got sprayed with hot coolant, and then had to close the stupid thing again. Wonderful. Best way to purge these (I've found) is to put the car up on ramps and open the radiator cap (cold, of course). Start the car and let it run a while. Once the thermostat has opened, it will purge any air present and you're good to go. If you need constant purging, there's a leak somewhere. Personally, I'm a believer in the Stant SuperStats now. Even if the faster warmup and better regulation claims are false (I don't think they are, but YMMV), the thermostat is about a dollar more than the bargain brand, has a jiggle valve built in and is well-constructed. I did two thermostats on my '95 Spirit. The first was an OEM thermostat that was sticking. The second was an AutoZone brand thermostat. I can't remember exactly what prompted me to replace that one, but when I took it out (after only a couple of months of service, mind you), the entire valve assembly had bent and was binding against the frame of the thermostat. I did not force the thermostat in, it slipped in as easy as you please and seated just fine. I don't know why it bent like that, but I do know that I will not buy another one.
I would not advise putting ANY sort of sealant in the cooling system. I've seen what it can do to an engine even when used properly.