Installed 180 thermostat now it misses and runs rough
#11
07-21-2021 | 02:14 PM
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From: Central Texas
A cooler thermostat won't help. Texas does not get to nearly 200 degrees. That's where your engine is designed to run. A lot of vehicles get tested in the desert with things done to make it even hotter. I talked to one Harley test rider who said when he was doing desert testing, it was a really uncomfortable feeling when he would hear the fuel between his legs in the tank boiling.
The new cap, rotor and wires are just good maintenance. A cold air intake will help a little, but you only have 6 cylinders and aren't towing a huge load so it may look cool at a car show, with your hood up, but it's working like the factory unit did with the same results. The 3.9 was well designed for what it was. All the first generation Magnums are based on the LA engine.
Ever since the late 1980's when fuel injection became common, people have tried to run a denser charge like on carbureted engines and they all lost fuel mileage. Some old hot rod tricks still work. A lower temperature thermostat isn't one of them.
The new cap, rotor and wires are just good maintenance. A cold air intake will help a little, but you only have 6 cylinders and aren't towing a huge load so it may look cool at a car show, with your hood up, but it's working like the factory unit did with the same results. The 3.9 was well designed for what it was. All the first generation Magnums are based on the LA engine.
Ever since the late 1980's when fuel injection became common, people have tried to run a denser charge like on carbureted engines and they all lost fuel mileage. Some old hot rod tricks still work. A lower temperature thermostat isn't one of them.
Personally, I think the factory air intake was an over engineered pile of junk in the first place. The cai I installed was mainly just to get fresh air to the TB period. Apparently the factory housing was made from the same crappy material as the dash, which I have also replaced. I repaired the factory housing more times than I can count with jb weld and fiberglass until finally there nothing left to repair. I didn't get it for looks I'm just going for functionality and trying to get the best bang for the buck out of this old truck. I try to maintain things rather than wait till something breaks and possibly breaks something else. I'm still learning about this truck and that's a good thing.
Last edited by HD Kowboi; 07-21-2021 at 02:23 PM.
#12
07-21-2021 | 02:32 PM
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From: Central Texas
I've always had good luck with "Aluma-seal". The plastic radiators today don't last long but this should plug the leak. It will usually last about a year or so. Open the radiator when cool then run the engine until the coolant is circulating. I'd make sure the heat is shut off so more stays in the radiator. Let it run for a bit then reinstall the radiator cap. This is if you are SURE it's the radiator. It might just be a loose clamp. You can put some UV dye to track the leak is you don't see the leak. UV kits are fairly cheap and handy to have around. Just make CERTAIN you use the yellow safety glasses as the UV light pen can damage your eyes.
I've seen people use "Barr's leak" but I've also seen it stop up heater cores. "Aluma-seal" is more temporary but works good. Now, if it keeps leaking, there IS an old hot rodder tick to make it last. Especially if the leak is at a seam where the plastic tanks meets the core. That is to loosen the radiator cap one notch. You will lose a little coolant and it will render your overflow tank redundant, but it will remove pressure from the system. You also won't have much heat in the winter. Make sure of what is leaking as it could be a loose clamp or the water pump is leaking from the weep hole underneath.
I've seen people use "Barr's leak" but I've also seen it stop up heater cores. "Aluma-seal" is more temporary but works good. Now, if it keeps leaking, there IS an old hot rodder tick to make it last. Especially if the leak is at a seam where the plastic tanks meets the core. That is to loosen the radiator cap one notch. You will lose a little coolant and it will render your overflow tank redundant, but it will remove pressure from the system. You also won't have much heat in the winter. Make sure of what is leaking as it could be a loose clamp or the water pump is leaking from the weep hole underneath.
Yeah I don't like putting anything in the radiator that might plug things that don't need to be plugged. I'll give the aluma-seal a try as I'm not a fan of bars leak.
Thanks for the input.
#14
07-21-2021 | 08:10 PM
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From: Texas
I went from a 195 thermostat to a 180 years back. Now, I'm sure ol' grouch is prolly right, however, I know plenty of 2nd gen Dodge owners that have gone to 180's to dampen the dreaded ping, myself among them. Mine's a 5.2 n I've noticed no difference in gas milage, quality of engine operation, etc. The next time I decide to change the therm, I'll prolly stay with the 180, just because. BTW, spark plugs are all still kinda dark brown n no misfires during extreme driving conditions either. I'm also in Texas.
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#15
07-21-2021 | 09:42 PM
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From: S.W. Indiana
Have you ever been to Texas in the summer? Lol, General Sherman once said if he owned both hell and texas he would live in hell and rent out texas.
Personally, I think the factory air intake was an over engineered pile of junk in the first place. The cai I installed was mainly just to get fresh air to the TB period. Apparently the factory housing was made from the same crappy material as the dash, which I have also replaced. I repaired the factory housing more times than I can count with jb weld and fiberglass until finally there nothing left to repair. I didn't get it for looks I'm just going for functionality and trying to get the best bang for the buck out of this old truck. I try to maintain things rather than wait till something breaks and possibly breaks something else. I'm still learning about this truck and that's a good thing.
Personally, I think the factory air intake was an over engineered pile of junk in the first place. The cai I installed was mainly just to get fresh air to the TB period. Apparently the factory housing was made from the same crappy material as the dash, which I have also replaced. I repaired the factory housing more times than I can count with jb weld and fiberglass until finally there nothing left to repair. I didn't get it for looks I'm just going for functionality and trying to get the best bang for the buck out of this old truck. I try to maintain things rather than wait till something breaks and possibly breaks something else. I'm still learning about this truck and that's a good thing.
I've had several 1990's Dodges, I have a '96 now, and I don't remember ever having the intake ducting come apart.
#16
07-21-2021 | 09:45 PM
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From: S.W. Indiana
I went from a 195 thermostat to a 180 years back. Now, I'm sure ol' grouch is prolly right, however, I know plenty of 2nd gen Dodge owners that have gone to 180's to dampen the dreaded ping, myself among them. Mine's a 5.2 n I've noticed no difference in gas milage, quality of engine operation, etc. The next time I decide to change the therm, I'll prolly stay with the 180, just because. BTW, spark plugs are all still kinda dark brown n no misfires during extreme driving conditions either. I'm also in Texas.
The only time I ever had much ping on a Magnum was when the timing chain was worn and the timing was off. A new timing set and the engine really perked up. Good heat, good power and the fuel mileage had me thinking someone was messing with me. 26 mpg on a '94 Ram 1500 with the 3.9. Repeated highway runs and it was consistent. I got 28 once on a flat ground run with few hills. I get about 1/2 that with my '96 and the 5.9.
#17
07-22-2021 | 06:26 AM
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From: Central Texas
#19
07-22-2021 | 09:46 AM
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From: S.W. Indiana
Well I addressed the pinhole issue yesterday and it appears to be holding for now. As soon as it gets light this morning I'll swap the old thermostat back in and see what happens. I just think it's odd how the radiator suddenly developed a pinhole after I installed the new 180.
It was probably about to cut loose anyway and when you messed around in there, you bumped something and it began to leak. Probably a little piece of crud was blocking it and when you drained and refilled the cooling system, it came loose. I've had it happen before several times. It's why I replace anything that looks iffy as once I get it back together, I'll have to pull it apart again.
#20
07-22-2021 | 10:29 AM
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Edit: I found some location info but still don't remember seeing it when I was in there. I moved the alternator both times and didn't see it so I must be blind or something. At least i know what to look for when I go in this time.
Last edited by HD Kowboi; 07-22-2021 at 12:01 PM.