Excess pressure in Radiator

[TomsSVX]

I am having difficulties pinpointing my problem. The raditator is getting too much pressure and it leaking out of the cap. The overflow hose is not clogged and the thermostat was just taken out today(left out for test purposes. My origonal theory was that the head gaasket was still shot and i needed to do it again but when using my NAPA block tester, I am finding no exhaust gases in the radiator. So i am back to square one trying to find out where all this pressure is comming from so anyone who can help please feel free to chime in.

[lee]

just to eliminate the obvious, have you tried a new radiator cap or had your's tested?

[oab_au]

If there was excess pressure, it still would not leak out from under the cap. Once the valve in the cap lifts, it should be vented back to the overflow tank. So either the cap is faulty, or the venting to the tank is blocked.

Harvey.

[TomsSVX]

well im gonna go w/ blockage to tank cuz i know the cap is good. ill check in when i am done

[SilverSpear]

Originally posted by tomssvx
well im gonna go w/ blockage to tank cuz i know the cap is good. ill check in when i am done

Check the water pump
if it is okay, take out the radiator and refurbish it !!, some of the sealings are letting some air inside... that's it
happened in my previous BMW

[TomsSVX]

the rad is fine and the pump is brand new.

[Bxsvx]

Even though its brand new, it still can be defective, saw it happen many times.

[TomsSVX]

yhe rad or the pump? the rad is out of my red fwd so I know t works just fine.

[SilverSpear]

try to put again the old pump. see if you have the same symptoms, then you have an air leak (air getting sucked from somewhere) in your cooling system. most probably the rad...

[TomsSVX]

I am not seeing how air could possibly be getting sucked in when there is over 20 psi(enough to make the cap leak) in my cooling system? I am going though a process of bleeding out the heater core because I was told that might be heating up air and expansion is causing all this pressure. My main reason for believing this is because I was not getting hot heat as I should have been. Anyway I will keep all of you updated.

BTW I do not see how the water pump could be faulty when all it does is move the coolant from one place to another, and that is happening just fine.

[Bxsvx]

I know on some cars theres a bleeder valve on the thermostat housing to remove air from the system. I dont know about the svx's though

[TomsSVX]

the thermostat is on the bottom of the engine. There is no bleeder on the SVX. To bleed the sytem you basically have to drive it and let the excess blow off through the overflow and keep filling the system. Im still doing that.

[Myetball]

Have you considered you may have a bad head gasket. If everything else fails, run a compression test on the engine. A leaking head gasket should show up as one or more cylinders low on compression.

[svxpert]

<<To bleed the sytem you basically have to drive it and let the excess blow off through the overflow and keep filling the system. Im still doing that.>>

Is this how you bled the air out of your system when you just put the water pump in?

[Beav]

Water pumps do not 'pump' or 'suck' air into a system. Good grief. There would have to be an extreme blockage of the water pump intake to cause/allow it to pull air into the system.

The rad cap has two gaskets - one seals pressure in the radiator, the other seals the recovery system. If the coolant is leaking at the cap there is a problem with that seal, the radiator surface or the return tube - just as Harvey was explaining.

Block Checkers, the type that work by chemical reaction with CO (carbon monoxide), don't work well in modern engines. The problem stems from the engine producing almost imperceptible levels of CO, as compared to older, carbureted engines. Either try spraying carb cleaner into the engine while it is idling to artificially richen and raise CO levels (enough to make the engine run rough) while using the block checker or remove the spark plugs and apply air pressure to the cylinders, one by one, while watching the radiator for air bubbles.

I do assume the engine isn't overheating? Isn't the SVX t-stat a bypass type 'stat? A lot of engines that employ that type of 'stat don't cool properly with a bypass type 'stat removed. I realize you removed it to check, but it may cause a different type problem in the process. Have you tried just watching for small bubbles while the engine is idling?