This is the first time I have posted on here and have seen a couple of responses to this problem, but I was wondering if anyone had seen this before. I have a 78 F-150 4 spd (1st gear is granny) that I am in the process of restoring. I just had the motor rebuilt which is a 351m bored out .030 over a little better cam just enough where it should still pass emissions and a 0 degree retard on the timing chain. New water pump, I didn't touch the radiator which is stock (which I believe is a 3 row) except for a new cap. During this process I took note to people putting on the head gaskets on reverse, backwards and so on so I made sure (or at least tried!) that the head gaskets where on correctly. Sorry this getting long.
Anyway, before I started this process the truck ran about average as far as heating is concerned. But now while I am driving it seems to run excessively warm, not at first but it will get up there where the needle will go just a little past "NORMAL" or stop right between the A and L. I thought about replacing the radiator with a 4 row, but then I stumbled on to something this weekend.
When I was accelerating I noticed the temp gauge start to drop. So I stopped at a light, started off like normal but left it in 3rd doing about 40mph. To my astonishment the temp gauge started to drop, fast, I went about 2 or 3 blocks and it fell back between about the N and O, once I shifted back to 4th it started going back over to the end of NORMAL and stays there, it really won't peg the temp gauge out. Anyone ever seen this before?? Is it a bad temp gauge or sensor?? Should I still swap out the radiator for a 4 row?? Any incite would be appreciated!

 

First, its always a good idea to install a new radiator with a new motor, or at least have the old one flushed (just imagine all that crud flowing through your new motor!!) I would get a mech. gauge and sender just to see some actual numbers. Ms tend to run on the warm side normally. Post back your findings.

Nathan

 

Well, i had the same problem. I would just start it up, and then I would go down the road, and I could literally see the temp gauge move all the way over, then max right out. I got out, and felt the rad. It wasn't even hot yet... I checked around with some other guys, and I found out it was a bad CVR (Constant Voltage Regulator). It is located behind the instrument cluster. It has connectors like a 9V battery. I replaced mine, and voila!!! It also made my Charge gauge, and fuel gauge work properly. Before they would always jump around.

Hope this helps!!

Later
Skud

 

Be sure to use a fan shroud and an effective fan. Are the pulleys still the original size. Faster rpm=faster water pump speed.

1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

I have had similar problems. Stop every couple of minutes as it is increasing in temp on your gauge and feel your hoses to determine if it really is circulating hot coolant. It may not be circulating due to a broken fin in the pump or a blockage of some sort.

 

Nathan,

Thanks for the input, I tried putting on a mech gauge my buddy gave me put it wouldn't fit. So I might try that yet again with a different one, we were going to have the old radiator flushed but we never got that far in the process. I will post back what I find out though!

Skud:

I don't think its my CVR, my other gauges work fine, although it might be something not making a real good contact. Thanks.

Beartracks:

Yeah I still have the fan shroud still on and the original fan. The pulleys are still the original ones. But you do have a point though faster rpm's the faster the pump is pumping the water.

Which leads to Bigblue:

I think you and Beartracks may be on to something that I may face having to do. Water feels like it is flowing through the hoses, but it may just not be enough, the radiator hasn't been flushed and looks rather beat up. I think I may just bite the bullet and get a new radiator this weekend for it.

Thanks guys I will let you know what I find out!

Rompen '78

 

[font size="1" color="#FF0000"]LAST EDITED ON 10-May-01 AT 05:10 PM (EST)[/font][p]If it really is high temp I would bite the bullet and get a 4 row. That solved my problems. I run a factory "flex" fan. You didn't mention the thermostat. I get by with a 195 year round with that radiator.

1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

Sorry about that Beartracks, I have a new thermostat in it, buddy of mine got it for me I beleive its a 160. When I do the radiator I think I may go for the 4 row, just better off that way I think, especially when I go four wheeling.

Rompen78

 

Well just to update you guys and anyone else that has ran into this problem, I replaced the radiator last weekend, and truck still runs warm, according the temp gauge. Not as warm, but it still gets over the end of NORMAL. I went out and bought a mech temp gauge and a new thermostat. It seems the only temp they had on that was 190. I will let you know what else I find out.

 

Well to let you know, I put in the mech guage and lo and behold the temp guage stops at 195/200! Still glad I put in that 4-row, to be on the safe side. I didn't touch the thermostat. Just happy that I don't have to tear into that bad boy now!

Thanks guys for your help and insight!

Rompen 78'