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Having the same problem (severely) with a 77 with a 460. Removed the thermostat, installed a new radiator. Don't suspect the water pump as there seems to be adequate flow with the cap off and watching the coolant flow. Is it possible that the fan just isn't spinning fast enough and needs a new clutch?
Last edited by Tamalpais; Apr 17, 2004 at 07:17 PM.
Reason: wrong location
Hey, thanks for responding. I just bought this truck so there's much I don't yet know about it. I assume it's the original shroud. It will show extreme heat on the guage after just idling for 20 minutes or so. I also don't know the fan, although it seems to be full size (fits the shroud with about 2 in clearance).
I'm wondering if the problem could actually be in the guage. I read a post that said a real over-heat problem would cause coolant to release via the over-flow hose but I haven't seen that happen yet. I will replace the thermostat and have some time to mess with the truck tomorrow. I will gather as much information about the cooling system as I can. Thanks again.
Last edited by Tamalpais; Apr 17, 2004 at 11:24 PM.
Reason: remove e-mail address
I gotta say that's a pretty good guess. It's fine when I'm driving and only overheats at idle leading me to suspect that fan just ain't spinnin fast enough.
Now I've got a stuck carb float flooding me out so a carb swap has become a new first priority. Never ends...
Tamalpais, the clue is that it does not overheat on the highway and that 2" clearance. You should have less than 1" clearance to the fan shroud, something around 1/2-3/4". Sounds like you either have the wrong shroud or fan. The fan is probably easier to get. Replace it with an OEM thermal clutch fan from the salvage yard. Don't let them charge you for the fan clutch unless it is good.
On closer inspection, it seems the only problem is with the alignment of the shroud. I just replaced the radiator and bolted the shroud on a little offset to one side (yes I will fix it).
I was planning on buying a new fan clutch from Napa. Any reason why not? Thanks.
Tried to post this yesterday, not sure what happened. Anyway, the next thing I want to go after is the whine in my power steering pump. A buddy tells me that there is a bleeding procedure that needs to be done after installing a new unit. First, are you aware of the procedure and can I do it myself. Second, can I try the bleeding procedure first, before deciding to invest in a new unit. Thanks.
Okay, I now have the truck and I installed a new Autometer electric gauge under the dash and left the factory gauge connected.
Took the truck out today in 90 degree weather and set in traffic for 1/2 an hour and the gauge never stayed pegged on 185, but the factory gauge did clime to the A in NORMAL. I trust the new gauge and it does appear that the factory guage was off as many had suspected.
I have not changed the flex fan with solid spacer over to the stock fan -- may not get to that for quite a while.
In the morning though when it was about 60 degrees, the new gauge stayed at 150 all morning until the outside temp got higher. Isn't this a bit low for operating temperature? Am I doing harm running at this temp?
Yes you are doing harm operating at 150F. Engine wear rates double for every 10F under 180 that you operate at. Therefore you are putting ~8 miles of wear on the engine for every one you drive. It makes the engine suck gas too. Get rid of the flex fan and check your thermostat. Get a 190-195F RobertShaw thermostat available form AUto Zone. Your wallet will feel a little better when you visit the gas pump.
It depends upon the condition of your cooling system. Some AF containers have charts on them but with a 15# cap a 50/50 mix will will stand 265F. That number will go higher or lower with changes in the ratio or pressure cap.
The temp your engine goes to will depend on cooling system condition, capacity, engine load, and ambient temperature.
The hotter the engine operates the more efficient it is. I would not worry unless it got over 240 with a normal engine under load.
Hot subject, no pun intended... I have a 1978 with a 460 but the gage doesn't move more than to the L on cool regardless of how I am driving it. Yet the huge 4 core rad will melt the skin off you if you touch it.
How do I test the factory dash gage to see if it is working properly?
There are specs in some repair manuals. The OEM manuals available on CD at the online store here have them. Most of the time the electrical connections to the gage have oxidized over the years.