Dodge truck overheating help

[ByronBob]

Try running it first without a T-Stat. That will tell you a thing or 2 before going further on.

 

[bgott]

Yep, $145 beats $222! I pay around $130 but I get mine wholesale through a body shop. Don't get carried away with the antifreeze. Antifreeze will help with boil over but doesn't transfer heat as well as water. 50/50 max. Another thing that I didn't think of last night. If your radiator cap is getting weak it'll let the coolant boil over. The reason for a pressure cap is to raise the boiling point of the coolant. It also will not let the syphon action take place that sucks the coolant back into the radiator when the engine cools. The water expands when it gets hot, passes to the coolant recovery bottle and then won't return when the engine cools down. A few cycles like that you start pushing coolant out of the bottle onto the ground. Don't make the mistake of filling the recovery bottle to the top. If the radiator is full you'll just waste coolant because of the above and if you have a leak the system will just pull in outside air rather than suck from the bottle. Check your coolant at the radiator when the system is cold, preferably after it has sat all night, then fill the bottle to the low mark or a little above. If the radiator is low after it cold and it has been filled and burped right it usually means you have a leak. Warning to those of you that aren't experienced in servicing cooling systems. Do not remove the cap when the system is anything but dead cold!!! Pressurized coolant, when hot, will turn to steam when the pressure is released and blow out all over you and scald your hiney. You'll only do this once, twice if you're ate up with the dummies! That new radiator probably will come with a new cap, at least the ones I get do. Test it anyway. Good Luck! /forums/images/graemlins/smile.gif

 

[rtimgray]

If I run it without the thermostat, do you have any idea what temperature I should expect? The only reason I haven't done that before - well, for one thing it was winter and I needed some heat, but mostly because it's about an hour or two to take out the t-stat - it's just hard to get to - take off the belt, take off the alternator, disconnect a couple of cables and lines, etc. and then the t-stat housing is down in between some stuff. I might give it a shot seeing as how it is warm weather season. Thanks.

 

[bgott]

Running without a thermostat on a full time basis is not a good idea. The engine doesn't get up to temperature so the moisture and volatile stuff that ends up in the oil doesn't evaporate and get sucked out of the crankcase by the PCV system. Then you have to figure in that the computer sees that the engine is running cold and adds extra fuel. More stuff to go past the rings and form acids and sludge. Then, once you load it and it gets hot, you don't have anything slowing down the coolant circulating through the radiator so that it has time to transfer it's heat to the air. If you are going to run without a thermostat at least change the oil more often. The easiest way to change the thermostat on that Dodge is to pull the A/C compressor. You don't have to disconnect the lines, just pull the bolts and move it out of your way. You won't believe how easy a job it actually is. Change out your bypass hose while you're there and look for coolant lines along the front cover gasket. If it still has the constant tension hose clamps use them and don't junk them for the screw type. The constant tension type are a pain but they stay tensioned when the hose shrinks to fit and you don't have to go back and tighten them. Once you reinstall the compressor you stand a very good chance of not being able to get a socket or screwdriver on the screw type hose clamps and then you have to pull the compressor again when the hose starts leaking the day after you install it. /forums/images/graemlins/mad.gif The last one I did, 6 months ago, was a water pump job that turned into a thermostat, front cover, water pump, hoses and radiator job. Every time I changed a component I would pressure test it and blow something else out. 165,000 miles with no maintainance. I crossed my fingers and didn't have to do the freeze plugs in the back of the block. /forums/images/graemlins/tongue.gif

 

[Soundguy]

Speaking of leaks...When my dodge 1500 water pump started leaking, I pulle dit and when I got the replacement.. I had a hard time sealing the metal pipe to block connection.. it uses an oring.. but the service guy said to rub some black rtv on it.. just a thin film.. that made my leak stop.. guess the casting int he block is a tad too porous for the oring to seal? ?

Any other dodge owners see this problem on a water pump replacement?

Soundguy

 

[rtimgray]

Well - here's where I'm at now. I replaced the sending unit, thermostat, upper and lower hoses and radiator. Started it up last night, added 50-50 coolant mix and let it run for a while. Temp gauge got up to about 240. Checked it with a heat gun and the t-stat area was only about 140. Took it for a drive - no change - got back and let it cool and then topped of the coolant (needed about another 1/2 gallon). Drove it around this morning and the gauge reads about 240 but the hoses and such aren't even up to operating temp (haven't taken for a 10 minute road drive yet, though).

So I'm thinking that I've got a bad gauge. I'me thinking of adding an aftermarket temp gauge (sunpro or something). Since this truck has two sensors (one for the gauge and one for the computer), if I just replace the one for the gauge on the dash, do you think it will have any effect how the truck runs? It doesn't seem like the truck is really overheating, I would just like to have a functional gauge in case it ever does.

Thanks for all the help and advice.

 

[Moon]

Sounds like your onto it. Is that a laser heat gun your using? Where do you find them and how much do they run. Sounds like something I need in my tool box.

Thanks,
Moon of Ohio

 

[bgott]

Have someone hook a scan tool to it and see what temperature the computer is seeing. Have you tried aiming the heat gun at the base of the sender? That will give you a better idea of what temperature the thing is running. If the thermostat is stuck closed or in backwards it'll heat up to 240 and the outside of the housing and the hoses will still be cold. Take the last thermostat you pulled out of it and get a pan of water and your wife's candy thermometer and hang the T-stat in a pan of water on the stove. Watch the temp as you heat the water and see when the T- stat opens. The temperature that the T-stat is rated to open is usually stamped on the end of the bulb. That's the copper pellet looking thingy that is supposed to go in the engine. /forums/images/graemlins/smile.gif If this T-stat opens like it's supposed to, stick it back in. Test the new one while you have it apart. Push the T-stat that you finally use open with your finger and prop it open with an aspirin. That'll let you burp the cooling system without heating it up and hoping the T-stat opens and the aspirin will dissolve and let the T- stat work normally. There is a chance you're getting a run of bad T-stats. This happens more often than you think. I've run into, off the top of my head, two or three bad T-stats in a row, five rebuilt starters, four out of spec coolant temperature sensors, countless rebuilt water pumps, A/C compressors, etc. After the second one you start thinking it's you! /forums/images/graemlins/tongue.gif Of course, there is the countless times that I have blown the diagnosis in the first place. /forums/images/graemlins/crazy.gif You have my sympathy, I've gotten into these kind of PITA's before and they can really drive you nuts, especially if your paycheck is hinged on it going out the door. /forums/images/graemlins/mad.gif

Yes, you can install an aftermarket gauge in place of the factory gauge as long as you don't inadvertently pull the collant temperature sensor rather than the gauge sender. You'll know if you do that because the check engine light will come on and it will be stuck on base timing. That's how you set the base timing on a Chrysler with a computer.

 

[rtimgray]

I'll have to see if I can find somebody with a scanning tool and the knowledge to use it - that would be curious to find out what the computer is saying the temp is.

Also as an update - now that I have driven the truck for a few days, it appears as though the problem has stabilized - so to speak. Prior to my working on it, the gauge would read anywhere between normal operating temp and pegging the gauge - no consistency. Now, the truck warms up to about 240, goes slightly over, then drops down (I'm guessing this is the thermostat opening) to slightly below 240 (I'm interpolating the numbers - the gauge only has 130, 200, and 260 marks). It then stays dead at this position, whereas before it wandered. When I have checked it with the heat gun, the hose reads 190; all of the times that I've checked it, I get it aimed down to the sensor and the manifold where everything (the two sensors and the t-stat) is mounted, and it all reads around 190 - and the thermostat is technically supposed to be 192 degrees, so that's pretty close.

Bgott-do you think the actual water temp could be 240 in the manifold and only reading 190 just on the other side of the t-stat? I mean, the t-stat should open at 190, but then if the water is 240, wouldn't that show up on the other side of the t-stat as well (I'm asking cause I honestly don't know if it's possible or not).

I know I got the thermostat with the spring side toward the engine side - that's the same way it was in before. Is that the correct way or not?

The laser heat gun I got from Grainger. It is a Raytek ST60 Pro Plus and it ran about $350 (luckily, my employer bought it - I actually use it at work and just borrowed it for this). I have seen some cheapies in Harbor Freight for about $70 - might be the trick for the toolbox.

Thanks for all the help and advice.

 

[bgott]

Yep, the spring side is the engine side. If you look in the middle of the spring you'll see the copper pellet. The water in the hose on the radiator side of the thermostat can be a lot colder than the water directly behind the thermostat because the thermostat acts like a barrier. If it isn't opening the heat will be disappated quicker by the cooler water in the radiator. It's kind of hard to pin down exactly what temperature you're going to see in the hose because you never can be sure what state the t- stat is in, closed or in a partially open state. It starts opening at 190 and slowly opens all the way at a higher temperature, probably over 200.