Hot running F-150

Tiny
HOTFORD
  • MEMBER
  • 1991 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 135,000 MILES
1991 f150 XLT Lariat Ext. Cab 4X4 Auto, Truck runs hot 210 to 225 deg. Engine rebuilt 4 yrs. Ago (302). So far it has a new radiator, fan clutch, water pump, hoses, 3 thermostats 195 deg, mechanical temp gauge. Two years back about.5 miles from home the lower radiator hose let go, I drove it home and temp gauge on dash reached the hot side. I parked it and the next day changed the upper and lower hoses, added new antifreeze. Started it up waited til it warmed up topped off radiator and recovery tank, put cap on. Took it for A ride temp gauge went over tward the hot side, to the L in normal and stayed there. For the last two years the above mentioned items were replaced one at a time with no avail. I installed the mechanical temp gauge to better see the temperature, thats how I got the temp numbers above. I checked it out with a inferred temp gun, the thermostat housing read between 205 and 210, various spots on the intake read about the same. Lower rad return hose red 120 deg. Inlet heater hose was 160 deg outlet hose 140 deg but I get very little heat in the winter? When the truck is started cold it warms up in the normal time range maybe between 5 & 10 minutes or so, thats idling not driving. You can watch the temp gauge climb up to 195 then you can see it drop off a few degrees when the stat opens, then from there it slowly climbs up to about 205-210 and stays around there. When you drive it it climbs right up to 220-225 then in a few minutes it drops back to 210 and then back up again, and it keeps repeating this cycle. It doesn't matter if you drive it hard or easy it still does this. One thing I find strange is that if I shut it down for maybe 2 or 3 minutes the temp gauge goes from 225 down to almost 180 deg like a rocket then climbs its way back up? Any help would be much appreciated. Thank You Mitch
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Tuesday, July 12th, 2011 AT 1:02 AM

8 Replies

Tiny
ASEMASTER6371
  • EXPERT
It sounds like you may have a head gasket issue. Also, when it was rebuilt, did you have it bored out and if you did, how much? If it is over bored out, it will always run hot from the thin cylinder walls.
Get someone to do a leak down test to confirm the head gaskets are good.

Roy
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Tuesday, July 12th, 2011 AT 2:57 AM
Tiny
CJ MEDEVAC
  • EXPERT
Thought I might add a little. Then I'll leave!

New stuff can be bad. Like the fan clutch. And I am usually the one that the defective stuff gets divvied to!

If your radiator hoses do not have internal "anti-collapse" springs. And they tell you they don't put 'em in anymore. They can collapse, or at least, I was the only unlucky one. Anymore, I'll pull 'em out of the old and stick 'em in the new one.

Shot the temp gun at the top of the radiator and found out the drop, as it reached the bottom?

Radiator cap?

And last, to keep my Jeeps ('77 258 and '46 Flathead L-134) circulating thru the radiator faster, I install a "Subaru" Thermostat, the same body as OEM, I have one in my hand now.I can post a pics if you want. All it says is "56mm" and "STC" on the bottom. It is like in 85% or more in any Subaru applications.I have bought many.I've done the homework, as to getting the one I want.

This thermostat has a "Door" on it the size of a Silver Dollar, or larger, where a standard thermostat "door" is about the size of a quarter

OK.I'm done preaching!

The Medic
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Tuesday, July 12th, 2011 AT 4:44 AM
Tiny
CJ MEDEVAC
  • EXPERT
OOOppppssss

I got carried away, like one of those blow up fun castles with the thermostat.

I was also wondering if you purchased the "1 Row" Eskimo Version Radiator or did you get a "Multi-Row" Sahara Version Radiator?

Or did the parts feller have a Cell Phone attack, and order you the wrong one, for your application?

The Medic
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Tuesday, July 12th, 2011 AT 5:06 AM
Tiny
EQUA ADANVDO
  • MEMBER
I agree with ASEMaster 6371 that you have posible head gasket issues. To be more precise restriction through the water pasage holes in the head gasket. If when the engine was rebuilt the builder used any thing like rtv sealant on the head bolts that go into the water passage then it is possible they are mooving through and getting caught at the smaller water passage holes in the gasket toward rhe rear of the heads. This will cause the hose to very likly collaps when what ever foregn material blocks the passage as it hangs up on the smaller hole. For many of you do not laugh. I have turned wrenches for 15 years and recently had this same issue after a knuckle head did this and when pulled down I had to pick out pieces of rtv even after taking out all expansion plugs and pulled both heads and flushed block with great force. NEVER use rtv or any other hard curing sealant on head bolts! ONLY thread sealant paste, only if theygo into the water jacket. NEVER gasket maker or rtv!
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Wednesday, July 13th, 2011 AT 6:58 AM
Tiny
EQUA ADANVDO
  • MEMBER
Oh and it was my truck that I trusted to the knuckle head and it cost me dearly. I did a complete rebuild as a result when all that it needed was the heads to be done and head gaskets. Expensive lesson not to trust other wana be's
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Wednesday, July 13th, 2011 AT 7:14 AM
Tiny
CJ MEDEVAC
  • EXPERT
EQua Adanvdo,

I can also be sympathetic to the overusing RTV thing, I have had to deal with it on another issue

Just wanted to sling out as many other possibilities as I could, generally if I do not respond to something, now, while it's on my mind...it slips away forever! (especially if I was not "on board", and did not get Email Notifications, and getting watch progression)

Many times working on my own stuff, if someone had just made one more suggestion, I might have saved much time, just by going back over the solutions, I thought might have been, already taken care of.

ASEMaster6371, DO NOT EVER THINK I'M TRYING TO "DEGRADE YOUR ANSWERS", or "SAY YOU ARE WRONG", I'm just trying to add to the "fix" possibilities, maybe to expedite the repair.....I welcome you and anyone else to jump on any of mine, to do likewise!....As this is, all about helping someone, who's about to be "afoot"......and we cannot let that happen!

Me being one of them, "cream of the crop, DIYers myself", I can sympathize with the lack of that "one little piece" of info, that someone failed to give me!

That's why you see me go overboard, so often....and yes many times I am wrong, but I do sleep well at night, knowing I tried my best!

This link is my RTV recent EVIL issue!

http://www.2carpros.com/questions/1992-jeep-wrangler-40l-squealing-noise-coming-from-transmission-or-transfercase

Your 2car buddy,

The Medic
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Wednesday, July 13th, 2011 AT 1:50 PM
Tiny
HOTFORD
  • MEMBER
As far as the engine rebuild goes, it was done by a professional mechanic with 25 years exeperience. It was bored out 30 over, all new pistons, rods, crank, cam, valves etc. The fact is the truck ran great for two years, no temp problems at all, then the lower hose let go, it over heated thats when the fun started. Right after I replaced the hoses it started to run hot, all the other parts that were replaced had no effect on the temp at all, so I think I will go back to the hoses and check for the spring in them see if they collapse ect.
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Wednesday, July 13th, 2011 AT 8:19 PM
Tiny
EQUA ADANVDO
  • MEMBER
I do understand that you had no noticable problems or issues for two years untill that fateful day the lower hose let loose. However many "professional" mechanics are not always good mechanics. Further after the motor over heated - "ran till temp guage reached the hot side"- this will cause all areas that no longer have water circulating to cool them, to reach extreem temps and will cause any harding sealers to posibly fleck off into the water jacket or passages. Do observe the hoses and see if either the lower or upper hose colaps. Often the lower hose will have the spring in it, however the uppers seldom do. It is worth paying to find another hose with one in it if nessisary to have the spring in both - (even if you have to buy a hose for another application and pull the spring to use in the upper hose). The only reason though that a hose will colaaps is due to a negitive pressure in the hose and this will only occure from somthing causing a restriction of flow or another way to state it is a flow rate that can not keep up with the pull from the water pump. If a lower hose colapses it is often a radiator blockage, however if it is the upper hose it is not from the radiator but either a t-stat or a restriction internal to the motor
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Thursday, July 14th, 2011 AT 4:56 AM

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