geo overheating

[thenn3025]

I need some help. Here's the story. Had 2 valves burn in my 3 cylinder. Replaced and repaired them. After putting back together car used alot of oil. Was told by GM mech that I was in need of a ring job, cause the new valve job raised the compression and the rings could not handle it. OK tore it apart and honed and replaced rings. Car runs great now but it can only go about 2 miles and it is overheating and pushing the antifreeze out. GM service manager said I probably had a cracked head because I have air bubbles in radiator. I wasn't sure about that as I could not see any cracks in it. Anyway replaced the head and guess what. It does the same thing it did before. Water boiling out of radiator. Does anybody have any ideas as to what I am missing? I have tried everything I can think of. GM service Man. is stumped also. Is it possible that the waterpump is sucking air from some where and pushing it in to the water? I could really use some help. Thanks

[zerocool1014a]

i would deffinately check the water pump.. my sisters geo was having a similar problem and well.. not too long after it started her waterpump blew... so i would deffinately think your on the right track with the waterpump

[geozukigti]

waterpump could be bad, radiator could be plugged, thermostat could be bad, cracked block is possible. Did you replace the headbolts and head gasket last time you put the head on?

[thenn3025]

Changed the waterpump about a year ago. It does the same thing with the thermostat removed. New head gasket not the bolts. Radiator has been flushed. I am getting a new lower radiator hose. I am thinking it might be collapsing. Gone a give that a shot. Got to thinking my overheating problem started when I put the new water pump on. Then I could go about 10 mi and the gauge would start to climb. By 20 mi it was boiling. Now it is about 3 mi.

[geozukigti]

Have your radiator checked too. It could be corroded shut. Also, when you pull the headbolts, always replace them. If they're stretched, they will give false torque readings when torquing them down, and will stretch more, causing a bad seal around the headgasket. You can pick a set up on Ebay for less than $20.

[BruceVW]

I had a similar problem with a '96 VW GTI recently, and the backyard mechanic that caused the problem insisted that I had a cracked head. A quick pressure bleed-down test proved that the head was not cracked.

The actual problem was just a blockage of the little 1/4" OD return line from the cylinder head to the coolant return reservoir! There is normally only a trickle of flow through that hose, but on many modern cars, it is the only path to purge the air from the cylinder head. On most 1.8L and 2.0L GTI's, a blocked return line results in large pockets of air in the head, bubbles and boilover of the radiator, and rapid overheating. The fix was simply to stick an eighth-inch drill bit into the hose nipple on the head and gently turn it by hand to break the ball of rust stuck inside. I've put another 30K miles (235K total) on it since then and haven't had a problem.

I don't know if this applies to Geos, but don't overlook the smallest of passageways when troubleshooting cooling problems.

Good luck.