Posted By: Pyper70
Chasing gremlins in cooling system - 10/07/12 11:06 PM
On the hunt for my cooling issues...I warmed up the engine today and hit 200ºF...I consequently shut the engine off and the viscous fan stopped spinning. I reached into the engine bay and the viscous fan still turns by hand. I know that if the engine was shut off and the fan was still spinning it was going to need replacing.
This was my first step since it didnt require removing anything.
Next up is the timing.
Is my viscous fan still good?
Does the the amount of blades make a difference? I have a 7-blade fan on the system now.
Posted By: Supercuda
Re: Chasing gremlins in cooling system - 10/07/12 11:15 PM
200 degrees isn't hot, why do you think you have an issue?
Posted By: bobs66440
Re: Chasing gremlins in cooling system - 10/07/12 11:20 PM
200* isn't dangerously hot. But if you have a 180* t-stat, then it's unusual and may need attention. If the cooling system is working properly, it should rarely go above 180* or whatever your t-stat spec is. I run a fixed fan, but from what I understand, when you spin the fan with your hand, if the fan spins for more than 1 to 1-1/2 revolutions without resistance, or if it does not move at all, you need to replace it. Some say 3 revolutions, but that seems a lot to me. Also if there's a lot of slop in it.
Posted By: Pyper70
Re: Chasing gremlins in cooling system - 10/07/12 11:44 PM
well last weekend my Autometer gauge rolled over past 240ºF and was heading for the 0 again...As it idles in park for 15 minutes
Posted By: Supercuda
Re: Chasing gremlins in cooling system - 10/08/12 01:02 AM
Swap it out and see if it works.
Posted By: terzmo
Re: Chasing gremlins in cooling system - 10/08/12 01:12 AM
if it cools good at highway or even long steady city speeds,the cooling system is working(Rad is good) but at idle or crawling along in hot weather You are not drawing enough air through the rad...hence the fan issue...so if the fan is not spinning enough to draw air...the clutch is weak and should be replaced.
Posted By: stumpy
Re: Chasing gremlins in cooling system - 10/08/12 02:21 AM
The thermostat doesn't control the high end of the temp. If you run a 165* stat you shouldn't expect the engine to run that temp. All the stat does is slows water flow until the engine reaches the stats open temp. If the engine runs above that,which most normally do, the stat will never close.
Posted By: roadrunner69s
Re: Chasing gremlins in cooling system - 10/08/12 03:49 AM
My '68 GTX 4 speed had similar problems with highway vs idle speed. On hot summer days it would run around 200-210 on the highway and at idle would easily get to 225 and keep going. Even after going through every cooling system component including a 3 row recore of the 26" radiator, nothing changed. I even got to the point of swapping back to an orig cam, rejetting the carb, advancing the timing, running a 98-100 octane mix, using infra-red heat guns, tighter gripping fan belts or better fitting pulleys, removing any vacuum leaks, and running 90% water with Redline water wetter. All of that helped....a little. After 3 yrs of trying I finally sold the car w/o ever solving the problem. No doubt an alum radiator with high capacity water pump would have helped some. It was annoying that between my Mopar mechanic and myself we could never find the smoking gun. The setup was basically stock with the proper 7 bladed fan/shroud and stock viscous fan. I do have to wonder if the new Year One repro fan shroud was part of the problem as they are not as deep as the originals, hence the fan blade protrudes out a tad. Could have made a difference. The idle engine vacuum ran around 8-12" as I recall which I felt was a symptom. Normal would have been around 14" or greater. My hunch was that a less than optimum fuel/air ratio was the source of the overheating.
Posted By: Mopar73340
Re: Chasing gremlins in cooling system - 10/08/12 11:51 AM
Both of my cars will idle at 200* all day long on a 100* day with the A/C on and a 195* thermostat with stock cooling systems. One thing that may have been overlooked is to be sure the fan clutch unit is a HD one for the 7 blade fan setup. I used to run the standard unit and had the same symtoms as described above and discovered the standard one will not spin the heavier 7 blade fan fast enough at idle or low speed. Not only is the 7 blade fan heaver but it has more resistance to turn as it moves more air.
Posted By: Pyper70
Re: Chasing gremlins in cooling system - 10/15/12 07:35 PM
I swapped out the old clutch for the fan with the new unit. i don't think anything was wrong with it but it doesn't matter. 15 minute job. I did bump the timing to about 18 degrees. (my timing tape somehow came off even though it was super glued on and clearcoated)...I need to perhaps try a little more...maybe 20 and play with the idle mixture screws a little. I got my vacuum up to 12" but I am also revving at 1100...So I need to bring that down with the next test and tune.