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Alrighty then, I am hoping someone can give me ideas on 2 separate issues I'm having?! First off, my oil pressure gauge is pegged out past 80 psi after start-up and will only drop a little after warm-up during idle. If I shut off the truck after it has warmed up, then the gauge will stay right where it's at, at 80 psi, but if I turn the key forward, but don't start it on a cold start, the gauge will start out at 40psi straight up. I have an oil pressure tester gauge that I attached where the OPS goes, then started and ran the truck for just a few seconds (therefore detaching my OPS from the motor, but it was still plugged in on the electrical side), and the gauge read "normal" oil pressure, but I didn't want to leave it attached with the OPS unplugged as I didn't know if that would throw my reading off or damage my lift or injection pump? Do you all think it's my gauge in the dash, or actually stupid high oil pressure? I have no overheating issues at all, in fact, just the opposite, but I'll get to that in a second. My fuel gauge goes past the full F and bounces around like crazy so I figured maybe the old gauge cluster is in need of replacement or fixing?
The second issue is that after replacing my OE radiator with a Champion Aluminum 3 row radiator and doing all the cooling upgrades listed in my signature, I have no hot air blowing out from the heater. I will also get the code P0126 Insufficient ECT For Stable Operation at times. I've heard or read somewhere that a possible fix to blow hot air is by limiting the flow of coolant that leaves the thermostat housing and travels to the heater core? I don't know. I've replaced everything else in the HVAC department as well. THis one is critical cuz it got cold real damn quick here in north eastern MO, and its no fun working outisde every day in the winter time and not being able to get into a warm truck!! Any and all ideas would be greatly appreciated! Thank you!!
 

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Did you bleed all the air out of the cooling system after the radiator install? This must be done or the cooling system will get air locked and cause problems like you are having. Air bleeder is on the thermostat housing.
As for the oil pressure. The sender may be bad. Or bad ground. Try replacing the OPS. use AC delco only.
 

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Um yeah, I'm pretty sure I bled the cooling system after I installed the radiator, but I can't remember for certain, so I'll look up how to do that and get that done asap to see if that works. I was gonna flush the heater core as well for giggles. I already replaced the OPS with an AC Delco one (had AC Delco already installed) and nothing has changed, still pegged out!
 

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I've redone all of the grounds on the truck awhile back as well, so I checked them all again and they are all good to go. I have changed the oil twice, so it's not the oil filter that has collapsed. I installed Leroy's oil cooler and braided lines whenever I installed the engine, so no kinks there. On the last oil change a couple of days ago, I went ahead and replaced all the seals onthe oil filter adapter and checked both of the oil bypasses and they looked to be good to go. So I guess I'm wondering if I can unplugg my OPS from the oil test port and plug in my oil pressure gauge and run the truck for more than a minute in order to make sure that the oil presssure in not really through the roof. Cuz if it's not the gauge, then the only othre thing i can think of is the oil pressure thing on the oil pump iteself thathas failed. Also, I found a TSB on AllData for the radiator stating that the OE radiator has a special restrictor fitting that limits the flow of coolant back to the surge tank. So I didn't know if anyone has experience this heating problem or not and what they did to restrict the flow of coolant?! Thank you!
 

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If you replace the OPS/sender with a test gauge (on a '99) or install a test gauge in another appropriate position with OPS disconnected, the PCM will continue to ensure the fuel pump remains in operation (normal b/u redundancy).


With regards the Heater.....did you do the dial and system operating tests in the truck manual?
You describe a 3 core aluminium radiator and cooling upgrades coincident with ECT codes/warning.....maybe you are not getting enough heat in the system in extreme cold to allow heater core to deliver warm air. Is the ECT coming up to normal temps at the same time you can't get hot air?
 

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Ok, great! I'll either plug it into the short hydraulic hose I have that extends the OPS or try and get it in the 2nd pressure test port right behind the driver's side head and un the truck for more than a couple of minutes to get a more consistent reading.

No, I think I have seen it get above 190* degrees one time in the middle of the summer whenever it was hotter than hell outside and I was hauling a huge load of scrap metal! For example, If I went outside right now (40* degrees outside), and started it and let it idle for 30 minutes the temp gauge would barely read above the 160* degree mark. If I were to go drive it, given that I drive like I normally do (I live out in the middle of nowhere so it takes a while to get anywhere a person needs to go and I have wayyy too much stuff to do to be driving the posted speed limits! LOL!), the temp gauge will only read a few ticks above the 160* degree mark as well. Whenever I drive it with my laptop plugged in with AE running, I will get up around 170*-180*.
 

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I think you should be getting warm air by 170-180 ect...ideal heater core temps/output are apparently above 190 ect.


I would do the dial/system checks in the truck manual....particularly to identify the heater core is getting hot coolant. You may have a blocked heater core or system blockage/restriction that does not flow coolant and therefore may not heat sufficiently.
 

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Pull the gauge cluster and make sure the wiring connector has good clean contact.
The OPS and fuel gauge will peg full if they lose connection to the sensors.
You can test the oil pressure gauge my unplugging it with key on, gauge should peg, grounding the tan OPS wire should read "0" psi. Driving with the OPS unplugged will not cause any problems. If you have no heat to the heater, stop and feel how hot the heater hose is as it comes out of the coolant crossover and where it returns to the radiator. The heat/cool door in the a/c box may be stuck.
 

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Discussion Starter #9
Thank you very much gentlemen! the good news is that after hooking up my oil pressure test gauage and actually running thetruck for awhile, I was able to determine that there is no mechanical oil lubrication failure, as the gauge read just as it should, so the problem is in the gauge cluster. I've been looking at an updated all digital gauge cluster from a company called Intellitronix, so maybe time to pull the trigger on that one. As far as the truck coming to operating temp and therefore allowing the heater to work properly, I plan on working on that one tomorow and I will keep this thread updated. Thank you again.
 

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Discussion Starter #10
Does anyone know where to find a coolant flow diagram? I can't find one anywhere, not even shop manual!
 
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