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2nd Gen Ram Tech1994-2001 Rams: This section is for TECHNICAL discussions only, that involve the 1994 through 2001 Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
So i have a 1997 Dodge Ram 1500 5.9 Magnum 4X4 and I just put a new thermostat because the old one was “stuck” open but it turns out the new one, which is the right temperature is not working right and its about 30 degrees out and the truck still only gets to 140 F on the dash and even the heater blows cold. What should be my next step?
On another not, the truck also bogs down to about 400 RPMs and sometimes dies when i put it into reverse or drive from the opposite gear position, the truck is an automatic and I’ve already changed the TPS sensor…
Can someone please help me out?
If you put a Failsafe thermostat in, you need to replace it. I've seen those fail the first time the engine warms up. It's possible you didn't get the unit and gasket seated properly. Get it a little crooked and water can go around instead of through the thermostat. I also drill an itty bitty hole (about 1/64) to allow air to bleed through in case of air lock if the unit doesn't have a hole or jiggle valve already.
First determine if the engine is really topping out at 140F, then go from there.
THIS! It may not even be the t stat. You can test t stats by putting them in a pot of water on the stove. You can simulate the temp change by shutting off the stove and turning it back on to see if the t stat works like it should. I have had the same t stat in my truck for the last 20 years(180* with a bleed hole) and not one issue. I actually went to the Stant web site and you can't even look up parts there. What are they thinking? I go there to see what's available from the source and now have to rely on a second or third party to get the info. Idiots! They have all kind of useless info there except the one thing you want!
You should also be able to watch live data while holding the upper rad hose. As it approaches the t-stat rating the upper hose should become noticeably warmer. Live data should show the temp drop and the hose should become cooler.
If the hose is just always lukewarm with little or no fluctuation, I'm guessing the t-stat is stuck open. I think ~140F felt through the rubber hose won't feel TOO hot. I don't think the rubber itself easily reaches 140F if the coolant is 140, although I haven't done any scientific mapping of such.
If the above checks out, make sure you see the blend door arm move behind the glove box as you adjust temp. The next question is if the door itself is actually moving. You can typically kinda "just tell" by listening for thunks or clunks within the box. You're moving a big flap in there, so envision what that would feel and sound like, vs a tiny arm connected to nothing.
If thar checks out, flush the heater core in both directions with a garden hose. Go back and forth repeatedly.
There's really only three components here:
1) the engine must reach a decent operating temp, say at least 190F. THIS IS YOUR SOURCE OF HEAT!
2) the heat must make it TO and THROUGH the heater core
3) the temp blend door MUST open properly to allow that heat to your vents
That's really it, except these trucks do have a 4th X-factor of cavitation -- air in the heater core is a possibility. If BOTH hoses to the core are warm and about equal temp, this is unlikely
You should also be able to watch live data while holding the upper rad hose. As it approaches the t-stat rating the upper hose should become noticeably warmer. Live data should show the temp drop and the hose should become cooler.
If the hose is just always lukewarm with little or no fluctuation, I'm guessing the t-stat is stuck open. I think ~140F felt through the rubber hose won't feel TOO hot. I don't think the rubber itself easily reaches 140F if the coolant is 140, although I haven't done any scientific mapping of such.
If the above checks out, make sure you see the blend door arm move behind the glove box as you adjust temp. The next question is if the door itself is actually moving. You can typically kinda "just tell" by listening for thunks or clunks within the box. You're moving a big flap in there, so envision what that would feel and sound like, vs a tiny arm connected to nothing.
If thar checks out, flush the heater core in both directions with a garden hose. Go back and forth repeatedly.
There's really only three components here:
1) the engine must reach a decent operating temp, say at least 190F. THIS IS YOUR SOURCE OF HEAT!
2) the heat must make it TO and THROUGH the heater core
3) the temp blend door MUST open properly to allow that heat to your vents
That's really it, except these trucks do have a 4th X-factor of cavitation -- air in the heater core is a possibility. If BOTH hoses to the core are warm and about equal temp, this is unlikely
A large enough air pocket will simply reduced the effectiveness of the heater core.... it won't transfer as much heat to the air, and it will cool quickly. On my truck, if I leave the fan speed on 3, I get warm air, turn it up to 4, and I get cool air...... I have yet to find an effective way to purge that air bubble...... Even parking at a truly stupid angle didn't really help.
And photo without caption. No one will remember this because no one on this board retains new information, but WTH I like wasting my time. We've got old dogs who can't learn new tricks, sadly.
What are they thinking? I go there to see what's available from the source and now have to rely on a second or third party to get the info.
Idiots! 
They have all kind of useless info there except the one thing you want!
