strange temp. spikes

[themadhatter]

Well i've been haveing some problems with the supra what happens is the temp. gauge is spiking to the red or very close then dropping back down to normal. So far i've changed the water pump and theremostat (clipped the dodad thingy off and positioned the hole at 12:00)but neither helped. I also checked all the coolent hoses for leaks and found nothing.
I did a compression check this after noon and heres the results
1-130
2-130
3-150
4-150
5-150
6-150
(redid the test twice to double check)
according to the tsrm the 130 meets the min. compession listing and there is no other sign of a blown headgasket (no white exhaustr smoke/steam or milky oil)
and i'm going to bypass the heater core in the morrning to see if that helps but besides that i'm out of ideas

 

[grimreaper]

block tester to be 100% sure.

20 psi difference is NOT within tsrm specs.

hows the radiator? old/new, clogged/cleaned, packed full of dirt in the fins? stock clutch fan? need a LOT more small stuff. list EVERYTHING you've done and what condition its in...

 

[suprashy]

I remember having an erratic temp. guage. The needle jumped up and down. It was the connector which is located in the water jacket or therm. housing area. IIRC, it is the long thin type. Verify that all your connections in that area are solid. Also, may wanna change your rad. cap....Stick with Toyo....
HTH.

 

[quake]

after checking to obvious, swing by a shop that does inspections and have them put the sniffer just above your open radiator cap when the car is running they should not charge you for this or not much $10.00. The numbers will jump up as soon as hc's are detected.

 

[Dakar2008]

are you burping the radiator when you fill up. or are you just filling it up once?

 

[themadhatter]

I went and bought a block tester kit like grim suggested and the test was negitive for HC in the colling system but maybe i did something wrong so i'm going to retest the car tommorow and dakar i bleed the system every time i refill the coolent.

 

[jdub]

What kind of thermostat? This looks like a stuck/sticky stat....especially if it happens most of the time on a cold engine.
I've gotten bad ones brand new out of the box. I test mine now before I install

 

[themadhatter]

the problem never has happened while the car is cold only happens when the car is fully warmed up and been driven a few miles

 

[jdub]

Here's what a sticky stat does: First start in the morning (or after a long sit), you drive 5-6 miles and the temp gauge rises to normal temp. Suddenly, the temp rises pretty quick all the way to near max. You pull over to take a look and it drops (stat decides to open).

When it does this next time, feel the rad hose before the temp drops...if it feels relatively cool, it's the stat. If the hose is hot, it could be either your fan clutch or a partially blocked radiator.

One more time...what kind of thermostat? I'm not going to keep asking the same questions over and over

 

[quake]

after checking all other options do as i said the block test does not show all leaks,