Rapidly Fluctuating Temp

[Joes4x4Ranger]

Last June I put a Motorcraft Longblock in my 91. Ever since, my coolant temp gauge jumps rapidly between the "O' in "NORMAL" and cold. The thermostat is the 198F that came with the longblock.

Over the last few days the temp fluctuation has been MUCH higher, now it shoots up to the "M" and then drops right back down the the line at the start of the "NORMAL" range. The water level in my overflow tank is always at the Full Cold line. It is the weirdest ****, I can fill it up to the top of the bottle and after a few days its back to the "FULL COLD" line and that is where it stays.

Ive checked the water level every day for the past 2 weeks and it is always at the full cold line regardless of the engine temp or how long I run the engine. I'm wondering if I should change to an aftermarket 160 or 180 thermostat? My thinking is not letting the water get so hot, the "cold shot" of water from the radiator wont be as severe, and the temp will actually stabilize.

Also ever since I put the engine in, my oil pressure needle is in the middle or "R". With my tired 200K+ blown head gasket old motor my oil pressure was always at the "L" in "NORMAL". Again I installed the new oil pump that came with the engine. I soaked it. Primed it manually before installing, and cranked the engine with the coil pack unplugged till I got oil pressure before I started the motor for the first time.

Could I have an electrical problem that is causing my gauges to be haywire? If so what should I start checking?

 

[alphamale]

Fluctuations

Howdy, put an external oil pressure gage on to see if you are within specks. The gages in these vehicles are not all that great.

As to the engine temp, i had the same problem with mine when I replaced the heads last summer. I had a big air pocket in the block. I ended up pulling the water pump and shoving my garden hose into one of the ports in the block and forced all kinds of air out of the block. It still does it a litle bit today but not enough to make the engine run hot. There are a couple of other people on this site who had simalar problems.

Good luck with it!

 

[walterd140]

Had a blown head gasket that I dumped the 'wonder stuff' into. It made some rapid changes as well.

Not to scare you, but just a heads up

 

[Joes4x4Ranger]

Alphamale, Do you think that air pockets will still be in my motor after 6 months and almost 4,000 miles? Is there any way to test to see if air is still in my cooling system? I don't really want to pull that water pump, is there another way to expel ALL the trapped air in my cooling system?

The cool weather is almost over here in hell, I want to get this figured out before the 100*F temps hit. We probably only have about another month of 60's and 70's. It'll be 90+ by March.