Hey guys, so I finally cured my 2.9 curse of misfiring etc and test drove her and it sounds quiet and smooth, but ran HOT on the temperature (according to my gauge anyway) I have now replaced the Electronic Temperature sensor and the sender... sadly NAPA lied said they had the quality more expensive ETC sensor but they didn't and I had to settle for the cheapo looking $20 not the $40 one I wanted don't know if I should trust it FYI. Still runs hot checked the radiator coolant (trucks been sitting since summer..) coolant looks old and nasty.. so I pulled of the cap followed by the drain plug shettlecock widget... NOTHING leaked out of the drain plug!! Poked in the hole with a small screwdriver and its covered with greenish tanish redish gunk consistency of clay! I've flushed it 3x now with BLUE DEVIL super cleaner gunk and it now has a slight trickle, but not even a steady stream.. (would rather replace at only $166) but spend that on my new battery, because the old one started smoking while testing it.

CURIOUS, So if i drive it around the block it will overheat to the H mark on the gauge... but it would idle at safe temperatures fine even for 2 hours with heater on high full blast in the cab,, So today I installed a new alleged quality thermostat and gasket and another round of FLUSH cleaner... now it looks like its draining slower then before and now it will also overheat even while at idle the moment I step on the gas a little... ALSO the cab air even though was on FULL BLAST Heat was cold air..

I admit I think I may have accidentally swapped the 2 hoses and installed them backwards, these hoses go to the firewall at the passenger side and attach to 2 nipples side by side and I think it goes to something called the "HEATER CORE" my brother spotted that and I swapped it back to where we "think" (i dont trust anything i do now with those stupid hoses) it suppose to go and same effect...cold heater, overheats easy... at least the fluid when drained looked nasty so we are cleaning it more..

But why these problems? Seemed better with ancient crapped parts...

Ideas, maybe my heater core is toast? fan clutch? someone said something about a valve on those 2 hoses that attach to the heater core?? I think its funny after I installed new thermostat i suddenly have no hot air in cab and worse heat problem. What I think is odd is that although the gauge SAYS HOT by my hand the engine bay still didn't feel hot to me. Also, i have a difficult time believing on a fairly cold engine just driving down the block it could over that fast...but i don;t know anything about overheating either.. so maybe false readings? But i have new ETC sensor and sender..


Any ideas appreciated,

Thank you

 



 

Sounds like you have a really neglected and corroded cooling system that is going to need extensive cleaning. When you start flushing the system, you are loosening up stuff that can get stuck in the radiator and heater cores. When you drain the system, you also introduce air, which needs to be burped out. That requires a system that flows freely. It may be necessary to change the radiator and heater core if you cant get them flushed. It does not matter on the heater core hoses to which side they are connected to. In fact it is recommended they be switched around before flushing the system and leaving them that way until the next flush. Leaving the thermostat out when flushing speeds things up with cleaning the radiator. Overheating the engine is never a good thing. You run the risk of damaging the heads or head gaskets.

 

Using flush kits help but it sounds like your radiator is really dirty. You will need to have power flushed at a radiator shop. Shop I use is about $40 and they do any repairs needed. If your cooling system is really bad you need to flush the block out. On that I do use the Preston kit to help flush it out with plenty of water pressure. Your heater core is most likely dirty. I pull the hoses off of the motor and flush both ways with just a garden hose. Changing a heater core on your 86 is easy. Just undo the clamps at fire wall and remove your glove box to get access at it.

 

I think I figured out why its so dirty... I bet the original owner spotted a leak in the radiator and they likely dumped a butt load of sealer in it.. I'm going to get a brand new radiator and heater core, I can get both with hoses for about only $200.. takes alot of guess work out. My only question is how do I flush the block out? I've never seen this done before, curious.. greatly appreciate your time thank you so much for your reply

KnightOwl

 

I am entering this conversation late... but make sure to flush the system again and again before installing the new radiator and heater core.

 

Ok guys, I didn't want a leaky radiator, I figured the original owner found a leak and dumped 5 gallons of leak stop, so I threw away the radiator and heater core and put in a brand new radiator and heater core properly flushed many times etc..
All went well and I needed it, so I test it... I start her up and let it "warm" up for about 1.5-2 minutes then start driving, after about 2 minutes according the my engine temperature gauge my engine heats up and goes to the top make for HOT...I don;t know much about engine temperatures but I don't even think a engine can get that hot that fast...the head is still butt cold... I did install a brand new Electronic Temperature Control sensor and sender... the sender was a high quality part but NAPA said they had the higher end ETC sensor but didn't was a cheap $20 that looked like junk... is there ANY chance this sensor although brand new is junk and giving me false readings? Like I said a 1.5 to 2 minutes idle then driver for 2 minutes and reads HOT HOT and the head still feels cold, and this was the first test of the cold day today, it has not run since yesterday ....

GREATLY appreciate your time, it has never sounded or run better but I want to figure this out and not chance it so I am not driving it back to work.. Any ideas? Thanks again guys.. As I write this I take note of RonD's post below under temp gauge issues..

 

I forgot too mention... it only seems to tell me its "HOT" or overheating once I drive it, sitting in the driveway it doesn't go to HOT.. could the water-pump not be working?

 

Well it was my "high quality" temperature sender unit, replaced it again and everything works perfectly!, I even fixed my dash and shifter, so it actually goes into park. Thanks for all the help guys! I am amazed how much faster and hotter the cab gets with a new radiator and new heater core, super awesome

 

I just mentioned on another post to a guy about new parts being faulty out of the box. One reason I use the highest quality part I can afford or find. Always be suspicious of reman parts. I have just started working on these trucks again after several years. I do not know the procedure on these trucks but air in the system can cause similar issues. Sometimes it is just squeezing a radiator hose to get air out of the system or other times it could be raising the front of the truck high and letting the thermostat cycle a few time with the radiator cap off to get air out of cooling system. Google burping system on your truck and that can help too.