overheating stumped mechanics

[smc2017]

92' 240 just replaced radiator, now overheats. new t-stat,coolant checked all hoses, bled,no smoke, oil clean pressure test..... heres the catch, it will not overheat for a week, and then it starts. check the radiator it's low. top it off runs fine, let it sit for a few hours run it again it over heats. doesn't overheat when idle, just when moving. Any ideas? I'm losing my mind.

[navysnail]

have you tested the pressure cap

[Nismo_Freak]

Possibly a leaking heater core?

[navysnail]

is there coolant on the ground were you park

[NISTECH]

the 240 can be a ***** to blled all the air out. get the front of the car as high as safely possible use a special bleed funnel you can get at some of the parts houses fill the funnel about half way start the car turn the heater on full blast and run the engine at 2000 rpm for 2 mins then let it idle for 10 mins check the temp of the air blowing from your vents should be hot. if not let the car continue to idle to allow it to cycle the t-stat a few times and purge the air out.

[navysnail]

dont forget about the bleed hole on the manifold

[smc2017]

Update... its been bled several times, i have had in the shop they can't find a problem. no fluid on the ground, no leaks from the water pump. replaced the overfill tank now it doesn't overheat but keeps eating fluid. oils clean no smoke or residue out the tail pipe. looking like head gasket, but not showing normal signs.

[navysnail]

if you are loosing fluid without it dripping, then its probobly the hg

[NISTECH]

doesnt the shop have a block tester? Its used to measure for HC's in the cooling system. Its a very simplistic tool.

[smc2017]

they say they checked it, and found nothing. Need a good mechanic not a parts swapper. I don't have the time myself to do the work. Looks like I might have to. ?'s the normal running temp. It still seems to be a bit warm. Thanks for the help.

[Q45tech]

I See your problem you are using a MECHANIC instead of a Qualified [in your brand] Certified well trained TECHNICAN.

If someone allows you to call them a Mechanic [without correcting you or explaining the difference] run away fast.

There is a serious glut of Mechanics in US but a very high demand for TECHNICANS.............few dealerships have very many real TECHS.

The word overheating is meaningless without accurate temperature reading within 1F resolution.

[NISTECH]

There is a serious glut of Mechanics in US but a very high demand for TECHNICANS.............few dealerships have very many real TECHS.

Aint that the truth!!

[smc2017]

not many techs in this area. dealer isn't worth a s***! Thinking about upgrading the motor. If it is the hg why spend 1200 on that when i can get a real motor and spend just alittle more. that i'll do myself! thanks for all the help.