1991 V6 Pickup

Left work this morning ang got down the road about 3 miles and noticed the water temp rising very fast. Pulled over to the side road and saw antifreeze sprayed over the motor. Had my dad tow it home and let it cool down. Couldn't find any leaks so I decided to start with the thermostat. Replaced that and it took 3 minutes at idle for the truck to over heat again. Let it cool back down and removed the radiator cap and cranked the truck back up. Within 30 seconds the truck start flowing water out of the radiator like a small fountain.

Something in the motor sounds odd but I can't tell if it is something coming from the timing cover or the motor itself. Pull the dip stick and oil cap and found no evidence of water.

What do you guys think? Water pump, blown head gasket, etc..........??

 

cap not holding pressure should hold like 13 to 16 pounds i think

 

I would tend to think water pump. Since you're hearing something that may be coming from the timing cover.

It's 6th on the FSM checklist for engine overheating. But everything that precedes it appears to be fine right? A blown head gasket's either 11th or 12th, depending on what they mean. It may not even be on the list if what they mean is a coolant passage blockage. I'm not sure what they mean, but I'm guessing they mean the latter. I can't see how a blown head gasket could possibly cause overheating(other than by causing number 1).

Here's the list:

1. Engine coolant leak
2. Cooling fan system
3. Radiator and radiator cap
4. Thermostat
5. Timing belt
6. Water Pump
7. Valve timing
8. Spark plug
9. Knock sensor circuit
10. Oil pump
11. Cylinder head
12. Cylinder block
13. Drive belt

http://personal.utulsa.edu/~nathan-b...63troubles.pdf

 

can anyone explain the fountain effect coming out of the radiator after 30 seconds? What might that indicate?

 

Sorry, I failed to mention that. It would also be pointing me in the direction of the water pump. But it might be due to something on the list that's ranked higher in priority, like say the radiator(since you just replaced the thermostat). It basically just means there's high pressure building up in the system. Which in turn means that high temperature, and/or a coolant passage blockage, is causing it. High temperature would be caused by lack of coolant flow, which could be because of a failed water pump or a blockage somewhere in the coolant system. If there's any blockage(s) it's most likely in the radiator. You could try back-flushing it to see if that helps. If it doesn't, then you might try replacing it before replacing the water pump.

I said water pump first because of the peculiar noise you seem to be hearing. Which doesn't make me think it's the radiator.

 

it could be cause ny the collant sitting in the block not circulating and it gets real hot and blows out the cap, if it has an air pocket it can allow for steam to build inside and force the coolant out the open cap

 

what about the coolant itself? if you are not running diluted anti-freeze would that cause an above normal spike in temp?

 

Blown head gasket( from the combustion chamber to a cooling passage)can cause your coolent system to become pressurized. It will cause your coolent to overheat and cause blowouts at the weakest point in the system( bubbling overflow tank , leaking radiator/ hoses ect...

 

I would check for water flow inside the engine when you first start, when cold. See if there is evidence of water circulation by the waterpump. If you prove that the pump is working properly then move to a blown headgasket analysis.

fjmudder1

 

Buy or rent a coolant testing system. I bought one from Sears for about $38.00

That's where I'd START. Can you describe or tape the "odd" sound?

 

*duplicate post*