So im pretty much at a loss here.

I own a 1990 bronco 5.0 and it overheats while driving on side streets, main streets, and highways. Along with that, my truck wont pass Nevada smog, and it has horrible acceleration. At idle it gets warm, but no overheating even after 15 minutes. It does overheat at idle while running heater/defroster though.

Ive replaced: thermostat 3 times, radiator, TPS sensor, EGR valve, all cooling sysyem hoses, water pump, water outlet, fuel filter, spark plugs, spark plug wires, timing belt, distributor, and entire exhaust system all this year alone.

i was told its not accelerating due to no flow from cooling system, but i dont know where else to even go from here after replacing dang near everything. Any ideas?

There are no leaks and timing is all top dead center.

 

Is your radiator cap functioning properly? If it's holding too much pressure you might overheat. Are you using the correct thermostat and it's installed the right way? Have you confirmed your heater core isn't blocked somehow? Also is your ECT sensor good? Sounds like you might want to pull some trouble codes and see if you have any.

 

I was able to make sure the correct thermostat is being used and while pulling codes the only one that ever flashed was related to the TPS sensor while engine off and engine on tests were ran. Since replacing those I haven't had a code.

How could I test my heater core to see if it were blocked?
I'm gonna attempt another code scan again just to make sure I don't miss anything.

 

Maybe when it's warmed up some, you can feel either hose attached to the heater core and see if one is hotter than the other; like if the flowing out is not as hot as the line coming in. If that didn't get you anywhere you could disconnect the two hoses running into the core, and run them together with a barb, then run the truck and see if it overheats.

 

Has all the symptoms of a fan clutch

 

Okay so both hoses felt equally hot to the touch and you could feel the flow through both. I still need to see if it is the. ECT as you suggested. Would the IAC have any plqy I'm this?

 

How am I able to test this fully? It doesn't spin freely and that really all I know to check for. Its only my top hose that feels like it isn't getting any flow and feels pressurized.

 

Is that a typo? In case it's not... IIRC, with engine warmed up and then SPOUT jumper plug removed, timing should be set to 10 degrees BTDC (BEFORE TopDeadCenter).
If you indeed have baseline timing set to 0 degrees BTDC (at TDC), I wouldn't be surprised the problems you are having.

Whether the heater core is plugged up, or free flowing, or removed totally and heater hoses jumpered together, it should have no real effect on engine cooling.
{Now, if someone was able to put the thermostat in backward, so it wouldn't open, then the heater core would indeed be the only "radiator" for the engine!!!}

According to old manuals I have, they say the only accurate way you can test a fan clutch is with a strobe light. The concept was to use the strobe light to determine actual fan blade RPM in two different heat conditions. When cool, the fan lopes along at a low RPM. When hot, the silicone fluid should expand and the fan should run at a larger fraction of drive RPM (it does not go all the way to "direct drive", just a large percentage).

My Bronco has the Factory Tow package on it. Years ago, I did not realize that the fan clutch was pretty much dead. The Super Cooling setup of the tow package seemed to cover it up well. But on checking A/C performance, I was getting 320 PSI+ on the high side, way too high for the ambient conditions. Spraying water into the condensor pulled the Hi-side way down, proving that the condensor was not getting proper airflow. I replaced the fan clutch, Hi-side pressure then was fine.

And then with the new fan clutch I noticed all the times I was sitting at a red light after high speed running, when light changed to green and I started to accelerate, all the fan noise! The new fan clutch was switching to near-direct-drive while I waited there, but I didn't notice because of just idle RPM. But add engine RPM, and that fan turns! Till enough air goes over the clutch, and it reverts back to loping along with air being forced through grill with forward motion.
Oh, yeah, the reason for telling this long story is that there was no way that I could find anything "odd" about the original clutch. Not spinning it by hand etc. etc. like I always heard.

 

So the fan clutch can affect the accelration of my truck as well? I'm gonna just purchase a new one after work and install it but I was just making sure if this is the cause of poor acceleration too.

 

No, a fan clutch by itself isn't going to cause poor acceleration just by it slipping, unless the engine is going into an overheat condition.
However, if you really ARE running base timing at TDC instead of 10 degrees BTDC, that will for SURE affect acceleration!

 

The timing is messed up, the fan-clutch is worn out, the head gasket has been blown, all these will cause overheating. Acceleration will only be affected by bad timing so that would be my first objective.