overheat issue

[slayer5]

Ok, I searched this board for answers to my prob....and and got some info, but I still need some more help. I have a 94' geo , runs great, starts on a dime, but if its hot out , which I live in Arizona, its starts to overheat, boil out the overflow...you guys know the drill. Ok, I have good radiator fan, no antifreeze in oil, if I take radiator cap off and start it, it has great flow after themo opens. So I assume the water pump would be ok. Also, if radiator was clogged, would it flow great ? I am wondering if it could be my cat clogged enough to restrict exhaust. Because the cat, pipes and muffle are all original. I have noticed a slight decrease in power. But it won't overheat unless I go 20 to 30 miles at 100 degrees outside. Could you give me some symptoms of what would happen with a clogged cat. Such as slight loss of power, or a change in sound or whatever you can say....
Thanks guys

[brivers]

I can think of only three reasons your car would overheat while driving assuming thermostat is good.
1. Lower radiator hose is collapsing at high rpm.
2. ignition timing retarded.
3. Radiator is partially clogged.
My money is on #3, It may look like you have good flow, but if its all flowing through 20 % of the fins you will eventually overheat. Flush or replace your radiator, and do it now before you damage your motor. Good luck.

[slayer5]

ok I will check those things out...here is another symptom...in the last 1 year I have gone through 2 sets of spark plugs. Not oil fowled, electrode damage, burned. Also, 1 month ago it was cold out after work, when I started it up , all other cars in parking lot was doing the steam out the tailpipe, mine was not. If you have any more imput, I'd apprieciate it.

[GM Line Rat]

Originally Posted by slayer5

here is another symptom...in the last 1 year I have gone through 2 sets of spark plugs. Not oil fowled, electrode damage, burned.

By burned do you mean "Black and Sooty" etc, or the electrode(s) were all/partially burned off the Plug(s)??? Take a look at this Spark Plug chart and see if you can tell us what the Plug(s) looked like when damaged?

Spark Plug wear Conditions

[slayer5]

closest one to what plug looked like was the "MELTED" one

[RossT]

I have seen with other cars, if the rad cap is bad, it will boil and overflow thru the overflow bottle. Make sure your cap is new and you don't have any air in the system. Also you may want to do a compression check just to make sure. Post your numbers here. You can buy a tester from walmart for about $25. Search this forum on how to do it.

[slayer5]

ok I will check it out, but pretty sure cap is good. I will be working on it this coming weekend.

[slayer5]

Hey, I went outside this morning and started it up without cap on to burp air out. What would be considerd alot of air ? Or at least enough to overheat. I'd get a cap size bubble then a couple small ones. This went on for awhile then it slowed up.

[GM Line Rat]

#1. Check the timing on this car 1st and see if it is set properly. This issue with the Spark plugs is NOT GOOD and soon you'll be needing a new head gasket if the car keeps overheating!!! Dont run the car Hot like this until you figure out whats's causing the overheating condition??? Here's a complete thread including pictures on how to Properly set a 3 Cylinder Geo Metro's Ignition Timing. If you dont have a Timing light, the local Autozone or autostore will rent 1 to you cheap so you can check it. Also, If your timing is off, you had better recheck your Spark plugs for any damage again? They may have to be replaced.........Again.......

3Cyl Geo Metro Timing Method


If the timing is set correctly, I Guess it's time to ask this Question: "How well does the heater work in this car when you set it to full heat and the car is warmed up? My then says that this car needs a COMPLETE Cooling system flushing including the Heater core in both directions, a new Thermostat in the proper temp range for summer driving and what Ross said (A New radiator Cap). The flushing will require you to drain out all the old antifreeze (Drian plug is on the DS bottom of the Radiator) and dispose of it properly, then (With the engine cold), Buy a Bottle of "Prestone Super Flush" and pour it into your radiator, fill the rest of the system with water, then run the car per directions on the prestone flush bottle. After completly flushing the cooling system out with clean water, remove both of your heater core hoses (Shown in the pic below), and run water thru the heater core in "BOTH" Directions (1 hose, then the other) until the water is clear coming out of the heater core. Reattach the hoses, then put in NEW Green anti freeze in a 50/50 "Pre Mixed" bottles from the auto store. Slightly elevate the front end of the car (Park on a slight hill or put the front wheels of car on a set of ramps). Then, with the heater on FULL HOT Position inside the car, start the car with the radiator cap OFF and let it warm up to operating temp in order to burp all the excess air out of the cooling system. Fill the radiator with the 50/50 Antifreeze mix as needed as the car warms up in order to keep the system full as air comes out and your thermostat opens. After the air is all out of the system, put the radiator cap back on and put the car on level ground again. Drive the car for a few miles, then bring it back to your house and let it cool all the way down again. Now take the radiator cap back off and fill the radiator as needed until it's topped off and there's the proper level in the overfloe bottle too! Drive the car for a few days and recheck the coolant level............Your done with the flush!

Heater Core Hoses





Geo Metro Cooling System



Another good timing reference thread
Ignition Timng.

[slayer5]

Well guys, I found out it was a blown head gasket. I had the head tested for cracks...no cracks but it was slightly warped. So machine shop milled it and I got the gasket kit, put all back together and presto.... all is well. No more overheating. No more sparkplug issues, no more engine ping. I want to thank you guys for all you assistance...