Engine not warning up to normal operating temp.

[CamoX413]

I'm having a problem where my engine isn't warming up to normal operating temperature. This all started after I changed my plenum gasket and added a Hughes plate.

Since I had everything taken apart I decided it was a good time to change a few parts so I installed a new duralast thermostat and coolant temperature sensor. Ever since then my gas mileage is in the garbage at 9mpg and my engine temp gauge only read about 160-170 at it's highest.

Anyone know how to determine which one is likely the culprit so that I don't have to tear everything apart and start guessing?

 

[Dean2]

Thermostat not working will make it run too hot. As long as you are in zero F or warmer weather your temp should get back up to full operating temp. Put a thermometer in your rad after going for a good drive, check coolant temp. Be careful taking off the rad cap, hot coolant is under about 15 PSI pressure. If you have a infra red temp gun you can just read the temp of the return hose and rad top tank. Low read is likely the new sensor being off.

Your poor gas mileage is not likely related to operating temp. I suspect your plenum gasket is not properly sealed, if it lets the engine suck excess air the computer will feed a ton more gas to compensate. Have had this happen on my new 94 V10 about 2 months after I got it, intake gasket went, as in nealry half the one side wasn't in its proper place. Truck still started and ran perfect but sucked fuel like crazy.

 

[CamoX413]

Thermostat not working will make it run too hot. As long as you are in zero F or warmer weather your temp should get back up to full operating temp. Put a thermometer in your rad after going for a good drive, check coolant temp. Be careful taking off the rad cap, hot coolant is under about 15 PSI pressure. If you have a infra red temp gun you can just read the temp of the return hose and rad top tank. Low read is likely the new sensor being off.

Your poor gas mileage is not likely related to operating temp. I suspect your plenum gasket is not properly sealed, if it lets the engine suck excess air the computer will feed a ton more gas to compensate. Have had this happen on my new 94 V10 about 2 months after I got it, intake gasket went, as in nealry half the one side wasn't in its proper place. Truck still started and ran perfect but sucked fuel like crazy.

I've read that if the thermostat stuck open it wouldn't allow the truck to go into closed loop therefore using more gas since the PCM believes the engine is still cold.

Is there a way I can check to see if it's the plenum leaking or an intake leak so that I don't have to tear into without knowing for certain the culprit?

I used all quality felpro gaskets and everything. Torqued it all down to spec. I've been driving the truck since then but my gas mileage is awful and the truck feels like it's lost a lot of power. I have noticed that the PCV has an enormous amount of air moving through it, so much that I can hear it in the cab. I don't know if this is related or not but thought it would be worth mentioning.

 

[Dean2]

Well, you can believe what you read or you can believe me. Your PCM is only going to over richen the fuel for a very short time at start and first bit of warm up. Even if the thermostat was stuck wide open, eventually the water temp is going to get pretty close to where it needs to be. Measuring the temperature of the coolant or return hose/rad tank will tell you what temp the coolant is at. I can't really help you if you won't check the stuff I tell you too.

Once you solve the temperature issue, you will pretty quickly know if that solves your gas milage or whether you need to go back after the intake gasket, but a lot of air through the PCV isn't a good sign and if you can hear airflow from inside the cab my odds on bet is you have a leak in the gasket.

 

[CamoX413]

Well, you can believe what you read or you can believe me. Your PCM is only going to over richen the fuel for a very short time at start and first bit of warm up. Even if the thermostat was stuck wide open, eventually the water temp is going to get pretty close to where it needs to be. Measuring the temperature of the coolant or return hose/rad tank will tell you what temp the coolant is at. I can't really help you if you won't check the stuff I tell you too.

Once you solve the temperature issue, you will pretty quickly know if that solves your gas milage or whether you need to go back after the intake gasket, but a lot of air through the PCV isn't a good sign and if you can hear airflow from inside the cab my odds on bet is you have a leak in the gasket.

I do appreciate your advice and will start with my multimeter and check the coolant temp sensor out and report back.

I'm going to do some research now on how to diagnose an intake leak. I'll bet you're right.

 

[crazykid1994]

Is it an oem temp sensor? If not the resistance reading could be off and throwing of the computer as well. May want to try swapping for a factory temp sensor. Also your pcv valve could be bad or the plenum gasket didn’t seal right. Or your intake gasket didn’t seal right. Did you use any rtv gasket maker on the edges and corners? I think you’re supposed to use rtv gasket on the front and rear gasket pieces as well if I remember correctly. Been a while since I did one. I think I used a light dab of rtv gasket on the intake gaskets to help hold them from shifting when I did mine

 

[Dean2]

Once you solve the temp issues, you can check the gaskets for leaks. Basically you take a pressurised can of Carb cleaner and spray it around where the two parts join. If it is sucking air you will hear your idle RPM change, increase, as it sucks in the Carb cleaner.

 

[CamoX413]

Okay so with the intake issue on hold for now and trying to solve the temp issue. Here's what I've found this far.

Update:

my interior temp gauge is reading around 160-170 but my scanner is telling me that my ECT temp is 91°

My scanner pulled a P1281 thermostat inactive.

Using a IR thermometer, my upper radiator hose is reading around 140° while my lower is cool too the touch and reading about 72°f

The two hoses going to the firewall are reading around 125-145°

 

[Dean2]

So, you are making good progress. New sender needs to be replaced with
OEM. The one you have is sending wrong info to guage and ECM. Thermostat is likely pooched too as the return hose should have no temp till you get above TStat limit of 190.

 

[GTyankee]

2 things that Ram trucks seem to like is a Mopar Thermostat & Fuel Cap

 

[Jim BB]

Okay so with the intake issue on hold for now and trying to solve the temp issue. Here's what I've found this far.

Update:

my interior temp gauge is reading around 160-170 but my scanner is telling me that my ECT temp is 91°

My scanner pulled a P1281 thermostat inactive.

Using a IR thermometer, my upper radiator hose is reading around 140° while my lower is cool too the touch and reading about 72°f

The two hoses going to the firewall are reading around 125-145°

Like mentioned in one post take carb cleaner spray around intake listen for RPM change if RPM goes up you have a leak but check all connections i.e intake manifold , vac hoses Throttle body spray all and listen that will help eliminate all connections !
as far as coolant goes Thermostat or air lock in system i think i would be replacing Thermostat With a OEM one and when you refill system make sure heat is on high !
when i worked at the dealer i have seen me take up to hour to hour and a half to blead out air system!

 

[Dean2]

Would love to hear an update on how you are making out with the temp and gas mileage issues.

 

[CamoX413]

Well, sorry it's taken so long to update. I just got around to tearing the truck apart today. The thermostat definitely isn't stuck open. I'm getting ready to run to the part store to get a new gasket and going to replace it anyway since I've got it out.

I called Dodge and the temp sender is on backorder and no telling when they'll have them. I'm confused as to why my lower rad hose isn't warming up if the thermostat isn't stuck open. If it were stuck open, I would think my coolant would be the close to the same temp for each hose since it would still be circulating.

If it were stuck closed, then I'd overheat which isn't the issue I'm having.

And what confuses me even more is if the temp sender is the issue with telling the computer and the gauge what my temp is then my coolant should technically still be circulating as the thermostat isn't controlled electronically.

 

[crazykid1994]

Well, sorry it's taken so long to update. I just got around to tearing the truck apart today. The thermostat definitely isn't stuck open. I'm getting ready to run to the part store to get a new gasket and going to replace it anyway since I've got it out.

I called Dodge and the temp sender is on backorder and no telling when they'll have them. I'm confused as to why my lower rad hose isn't warming up if the thermostat isn't stuck open. If it were stuck open, I would think my coolant would be the close to the same temp for each hose since it would still be circulating.

If it were stuck closed, then I'd overheat which isn't the issue I'm having.

And what confuses me even more is if the temp sender is the issue with telling the computer and the gauge what my temp is then my coolant should technically still be circulating as the thermostat isn't controlled electronically.

The lower hose should never be “hot” as that’s the output. Your radiator is cooling the coolant down. That side should definitely be cool. The upper hose should be hot. And pressure should build in the hoses. You could try installing a physical analog gauge just for craps.

 

[Dean2]

Did you ever figure out if you had a head gasket leak and did you get the cooling sorted. Merry Christmas to all.