I drive for about 20 min and the temp will go up, come to a stop and it goes back down.Water is being pushed into the overflow and bubbling when hot but sucked back in when it cools down.It can idle all day long and not overheat. Radiator is not clogged,new waterpump,new radiator cap,removed thermostat and new head gasket.Did a compression test all four were within 20psi of eachother.No coolant leaks and fan is working.I bled the coolant system but didnt help.No water in oil or oil in water.Could there be a clog in the cooling passages of the motor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by E_F_9 &raquo;</TD></TR><TR><TD CLASS="quote">I drive for about 20 min and the temp will go up, come to a stop and it goes back down.Water is being pushed into the overflow and bubbling when hot but sucked back in when it cools down.It can idle all day long and not overheat. Radiator is not clogged,new waterpump,new radiator cap,removed thermostat and new head gasket.Did a compression test all four were within 20psi of eachother.No coolant leaks and fan is working.I bled the coolant system but didnt help.No water in oil or oil in water.Could there be a clog in the cooling passages of the motor?</TD></TR></TABLE>

A clog is possible, especially with things like cheap aftermarket coolant & tap water - the chemicals will burn out and collect in places. Older motors can potentially have pieces of debris in them from various crap over the years.

I wouldn't think its the most likely thing, could you describe how exactly it's overheating? If it isn't at idle, have you checked all of your heater hose?

Bled the system for air bubbles properly?

 

driving highway speed for about 15-20 min it rise pretty quickly and stop right before the red and sit there.If i let off the gas it drops a little.If i come to a stop it drops alot sometimes but immeditaly rises when i accelerate again.I turn the car off and the overflow is full of water and lots of pressure until it cools down then it sucks the water back in. im lost

 

so driving home from work today it was fine for about 5 miles then it started to rise to about 3/4 hot,it only sat there for about 5 seconds and dropped fast back to half. sat at half for a few minutes and slowly rose back to about 3/4 maybe a little over but then i was home so i shut it off

 

check rad cap,thermostat and maybe Radiator pressure?

 

Try this.

Take it for a drive. When it starts to heat up, turn on your heater full blast(defrost setting so you don't burn up in there too bad).

If the temp comes down more than likely you have air bubbles in the system or a bad rad cap. Let it cool down. Jack up the front of the car so that the radiator inlet is the highest point and let the car run and visually check to see if any bubbles come out. Be patient. Sometimes it takes a while for those bubbles to come out. Keep filling it with coolant as well as the bubbles come out.

Have you checked the thermostat? Let the car warm up and see if the fans kick on...while the car is warming up you should feel the upper hose get very warm and the lower hose is gonna be cold. If the lower hose stays cold even after the fans kick on then you got a stuck shut thermostat.

 

im just gonna swap heads because that is the only thing i havent tried, i guess it could have cracked or warped when the water pump went out originally. I have new rad. cap,took thermostat out,bled the system,tried different rad. new head gasket and new water pump

 

100% its a warped head...i just had the same problem and it costs alot of money to try to find the problem.....trust me.!!!

 

luckily i have plenty of heads

 

You can rent or buy a Combustion Leak Detection Kit to see if you have any exhaust gases in your radiator coolant caused by a bad head gasket, cracked head or block.
Fluid changes from blue to yellow when exposed to combustion gases from the radiator.

Also the 20psi difference from the pistons seems like a lot. My guess is that something was missed when replacing the head gasket or there is a crack on the head.

If you decide to replace the head, make sure you have the head machined, install a new head gasket, and tighten the head bolts to specs. Good luck

 

T-stat?