had to replace heater core on my 68 ranger.now the engine temp. wont get above 130-140 degrees.if its real cold even lower.takes forever to heat up.warm air does blow out but not hot.i pulled the stat and it checked out fine, replaced anyway.still same thing.this truck always had good hot engine temp.180-190.perfect.the gauge is fine, as you can tell after a long drive that the engine doesnt even seem hot. whats-up?

 

sounds like the thermostat is stuck open, It will take forever to warm up. I don't know how a heater core would affect that though. Check to make shure ther is no restriction in the heater lines, also check the valve in the engine compartment and check that it is not stopped up.

 

Wouldn't be the first time I saw 2 bad thermostats in a row. Try a different brand? Make sure it's a 190 or 195.
Gene

 

Another possibility is the thermostat isn't seated in the water outlet . I've had them slip during installation which allows the coolant to bypass the stat. Usually they will leak but not always.

 

You can test to see if it has anything to do with the heater core by connecting the 2 hoses before they go through the firewall. If the temp goes to the normal range its the heater core if not its something else. you might need some fittings to connect them should be able to find every thing you need at a local hardware store.

 

I have always had to run cardboard in front of the radiator in the winter on FE's. I never could get any heat out of them otherwise. I always blamed the bypass hose on the water pump.

 

Does the thermostat open?

Boil some water on the stove, toss in the thermostat...then watch.

Genuine Ford and some aftermarket t/stat's have whatever the particular t/stat's degrees are, stamped on the element.

Example: A 192 degree t/stat will have 192 stamped on the element.

Careful what you buy, parts have been known to be mis-boxed.

 

i have had this happen to me tons of times now. in washington during the winter i ran a 205 degree thermostat, then duing other months i'd have 185 or 195. so musical thermostats. down here in florida i might do a 170. i always clean the surface of the intake area real good, then put the gasket down, and a smidge of rtv silicone and put the thermostat in place, this holds it, then i slap on the thermostat housing and bolt it down snug, come back an hour later, torque it, then fill er up with antifreeze.

 

You didn't say how cold it was outside when you had a very low eng. temp. I've had to block off 1/2 radiator when it got down in the 30's temp with a 180*stat . I have the 26qt. system large C/S radiator. Plus i'm running a clutch fan, So it maybe the change of weather. Did you which coolants. Most poeple don't know that Plain Water will run much cooler then a 50/50 coolant mix... my2cent
orich

 

well I have never heard of a Motor running to cold unless it wasnt set up right for the climate inwhich its running... with our trucks we have to realy on mechanical parts to make our Trucks run right..Not like the new Computer controlled vehicles...

When I drove my Truck in SoCal, I ran it with a 165 T-stat in it..as I was carrying a Camper on it (Big Overhead) and either towing the Race car, or the boat... and I alway ran a 50/50 mix of coolant...

Now that I moved to South Western Virginia.... I run a 195 T-stat in it with the same 50/50 mix without issues... But with that said ....My 70 F250 is still cold blooded as is my 4x4 Power Ram... takes about 20 mins to get any heat (low at that) coming out of the heater core !

But now my wifes 02 Pontiac, I can go out and start it with snow on the ground...Come in the house and get my coffee, By the time I get into her car, Its already blowing hot air!! and its runs at 195* in the winter and about 200* during the summer with the A/C on... and just on a foot note: If your temp gage is factory ? at being 41 years old..I wouldnt trust it as far as I could throw it!!

I went to all mechanical gages after my truck was about 10 years old... I would dis-connect..Block off the heater core at the firewall with some hose going to each nipple! and back flush the ***** out of the block and radiator until you see clear water coming out of the pitcock at the bottom of the radiator...and then before you hoof the heater core back up...Fill the block and the radiator up with just plain water... with the Radiator cap off, Look for a good moving cross flow going horizontal across the radiator tank !!

When you see that you know all of the block is clear of most debre and the water pump is also doing it job !! Hook the heater core back up....and drain the system again...and refill it with the 50/50 mix of your favorite coolant !

I have also run across some of the older blower motors only running at about 50% of the new speed..and give the feeling that your not getting much hot air out...I guess alot of guys dont realize these trucks are getting up in age... JMO..

~Russ