I got a 80 f-100 custom, my head gasket blown on it not to long ago then my radiator and my water sendin unit, i had all that fixed, new over sized radiator, the 4th 195 thermostat, water pump hozes sendin unit, now my temp gauge registers almost hot it usually stays on the end of the word normal, ive had it checked several times no one knows what the deal is, its possible the block has an internal crack. the mechanical gauge registers 190-210 moving all the time up and down depending what the speed limit is. it hasnt boiled over yet. is it possible to but a 5.0 v8 in it. does anyone have any suggestions. God bless you for your help!

 

forgot to mention tis a 300 4.9 in line 6

 

have u checked to make sure the water pump was working okay i would assume the faster u go the more revs ur pushin therefore the water pump will work more maybe the belts not tight enough or something having to do with that issue. also the faster u go the more air flowing over the engine and radiator maybe the thermostat is just defective can u take the theremostat out and just let it run w/o one?

-Dusty

 

maybe ur gauge is wrong or something but dont get rid of the 6 its much to good of an engine to let go. but if u want i am willing to take it off ur hands,get ahold of me,just email me,but ya if can dont get rid of the engine

 

Just a thought but could it be that the head gasket was installed upside down blocking off some of the water passages..... i know on the 302 there is a specific up and down side marked on the head gasket......just a thought

 

Seeing how it runs back down to the normal range one you shove some air through it at speed, I would be looking at the fan shroud (got one?) or the fan clutch is out. When the truck is hot and idling, will it hold a red rag flat to the radiator?

 

my water pump is ok i put in 2 factory gauges and they register the same thing my truck is acting like there is something blocked in the engine block. i may go down to a 160 thermostat that is what it has done best on. it runs good in the morning but not when it warms up outside. the temp moves all the time up and downit gets hotter going 65 and 55 but does about 190 when going 35 to 45 and gets hot when it idles the fan shroud is the original my fan runs on belts it has no fan clutch

 

A thermostat mounted upside down can cause similar symptoms. Sensing (spring) side goes toward block.

 

Did you use "Stopleak" in the engine at all before the head gasket replacement?

Try having the cooling system backflushed, with a good quality backflush additive. Prestone etc...


Check the lower radiator hose. see if it is soft. The hoses could be colapsing.


Are the fins blocked with bugs and crap in the old radiator? Take the radiator out and blast it clean, or take it and have it boiled out.

----------

You probably have the standard Small square Radiator, no fan shroud, (Just a guard on top). They are nortoriously prone to overheating, even when they were brand new.

What I did to eliminate this problem, of having a too tiny radiator is the following.

#1: I bought a new Super Cool Radiator. (Standard for air-Conditioning Models)

#2: Bought a new top radiator hose, cause the old one is too short to fit the longer raditator.

#3: Bought a new Fan Clutch. (Truck didn't come with one)

#4: Bought a Fan Shroud, Radiator Fan for the Fan Clutch, and a Radiator Support for the larger radiator (Hole in radiator support is larger for the bigger radiator) out of a junk yard truck.

Spent the day, painting and bolting it all in. hasn't overheated since.

 

Just re-read your original post. 190-210 Deg. F. on a good mechanical gauge is fine, you're probably just seeing the normal temperature fluctuations due to the 195 Deg. F thermostat opening and closing. You'd never see that on the stock temperature gauge because it is designed (long time-constant response) to mask out the short term changes and just indicate average temperature over several minutes. If you replaced your temperature sending unit with an aftermarket unit it may not match your gauge parameters exactly and cause a high reading. Over the years I've had good results with the ones NAPA sells, not so good with others. If your oil pressure and fuel gauges also tend to read high, then suspect the Instrument Panel Voltage Regulator; it supplies regulated voltage for all three gauges. If you really want to test the gauge circuit, get a 22 Ohm (or 25 if you can't find a 22) wirewound resistor (from electronics supply store) with a power rating of at least 5 Watts and temporarily substitute it in place of the sending unit. With the resistor in place of the sending unit, the gauge should read mid-scale (this works for fuel and oil pressure gauges too).

 

aight thanks for the info piffery1, my dash panal as idiot lights in it the lights work better than the gauge does my old sending unit registered cold when it warmed up and never gave me a problem it was that way for 24 years now all this new stuff isnt working in it now it has so much pressure in the engine everything leaks. it a mess but i hope i can get it workin