Fluctuating Temp

[Flip4ford]

Well I noticed on a 200 mile trip today that my temp guage floated between "o" and "L" in the normal range on the temp guage. It used to stay rock solid at the "R". When I say flaoted I mean 1 minute one letter next minute the other. O stopped and checked fluids and the radiator cap "Looks" good. Just wondering if anyone had any thoughts?

 

[surf]

The three things that I can think of that might cause that condition are air in the system, a failing radiator cap or a bad temp sending unit.

 

[Tbars4]

..A couple more things would be a sticking thermostat, the vains on the water pump are disappearing or, your fan clutch is heading south..

 

[backfrmcolorado]

Having the same problem with my 92. New temp sensor and stat with new coolent flush and it also "floats" around. Signing on to this on

 

[Tbars4]

..:scratch:..Another item I forgot to add which is very common and often overlooked is a blockage in the heater core...It seems sediment likes to get caught in there either blocking the line or eventually wearing out the heater core..

..Sometimes the sediment blocks the line till enough pressure let's it pass thru until it eventually gets clogged..

..A lot of times a "Flush" will loosen particles from one place and deposit them to the heater core..A loose particulate could also foul a new tstat..

 

[Xeek]

figured id add mine in here. mine is similar except it goes past the L almost towards the HOT marking.. then goes back down. and my coolant seems to be disapearing also. im thinking it was a failed attempt at burmping? im not sure where the weep hole is but the water pump is about the cleanest part on the engine cause its new. so i didnt see anything dripping

rad is new, hoses are new, water pump is new. old owner had it done.

i flushed it yesterday and put in a new 190* motorcraft thermostat. havent had enough driving time to see if it resumes yet. i burned it til i only had a few tiny bubbles this time, using a large funnel.
and when i say flush, i mean run the truck using a flush kit in the heater hose. take the heater hoses off and spray down each hose. spray down into the heater core directly. spray directly into the thermostat hole on the intake, with it removed. all of that til the water was completely clear


one thing tho. my fan is cracked to holy hell. would that cause every bit of the problem?

 

[Brian1]

one thing tho. my fan is cracked to holy hell. would that cause every bit of the problem?

Better replace that now before it fails and you have bigger problems - fan blade going through your radiator for example.

I recently had a similar problem, it would run hotter than normal and fluctuate between n and the a. I had newer hoses, pump and radiator. I ran a pressure test and confirmed that the system was not holding pressure. It was leaking out the gasket between the timing cover and the block which is a common problem on these engines. I replaced the gasket a few weeks ago and while I was at it put in a new t-stat and new cap on and problem solved.

 

[Xeek]

yea. im just not sure if i need a new clutch or not to. mine works, but i dunno howto tell if its heavy duty or standard and i know you have to match the fan with it..

i know exactly the place youre talking about. had to look at pics of my engine build, i dont see anything in those areas. the water pump is clean all the way around.
i may have found my leak tho.. i saw green on the bottom on the rad. near the lower hose. the rad itself, not the plastic. i may have a hole in it. i got some stop leak that worked wonders for the gaping hole i poked in the exploders rad with a tree. so ill try it on here and see.
im dreading the fan nut and wrench. i gave up on the exploder and got a new water pump and pulley and threw the old setup away as one piece lol