cooling system problem

[lhcolts]

Hey Joeg, Im having the same exact problem as you did with the cooling system in my 2000 ford ranger 3.0 v6.it just started this week after I took it to a repair shop and had them do a radiator flush. They have been no help,and I guess its my problem to resolve. I have changed the thermostat, new radiator cap and replaced the heater control valve. I then Took the hoses off the heater core back flushed it with air.I had great heat after this and it did not give me any problems the rest of the day. This morning it did the same thing it has been doing first thing in the morning when i leave for work. the gage starts to rise just past c and then nose dives to cold for a mile then jumps and pegs hot for a mile or so and then falls to its normal operating range. I have no or very little heat when this is going on. After i get to work I pop the hood and it has filled the reservoir with coolant and blown the top off and shot coolant all over the engine. It has 147,000 miles on it . I have not replaced the water pump yet. Some people say it could be a blown head gasket ?.The truck runs great and the oil looks fine.This has me stessed out as we do not have much money for an expensive repair bill. How did you correct the problem in your truck Please help Thanks Lonnie

 

[RonD]

Simple test for blown head gasket:
You will need a sandwich bag or latex glove

With engine cold start it up
Remove rad cap and overflow hose from rad
Place baggie or glove over rad cap opening and pinch it tight to seal
place finger over overflow outlet

If baggie or glove starts to inflate you have a compression leak from piston cylinder to cooling system, blown gasket or cracked head.

There is no pressure in a cold cooling system, coolant heating up is what gives the system pressure.


Heater blowing hot and cold means air is in the cooling system, could be pushed in by a bad head gasket or just air from not bleeding the system.

 

[lhcolts]

Cooling System problem

Thanks Ron,Ill give it a try. How long do you have to wait to see if bag will inflate or does it do it immediately.The last time I ran the engine was around 11:00 am.How long should I wait before I do this test.

 

[adsm08]

Results should be pretty quick.

 

[RonD]

yes, it happens pretty quick, especially if its a big leak from a cylinder.

And warm engine is fine, as long as coolant is not expanding and overflowing the rad which doesn't happen until coolant is hot.
Cold engine/rad is just easier to work with.

And not that it matters at that point but if baggie does inflate you can ID the cylinder that is leaking into the cooling system using the same method.
Remove all spark plug wires
Remove all but 1 spark plug
If you are alone use a rubber band to hold baggie or glove on rad cap opening, and vacuum cap or hose with bolt in it to block over flow outlet

Turn over engine...watch baggie
remove the spark plug and put it in the next cylinder
repeat until all cylinders are tested

Baggie will dance when spark plug is in leaking cylinder, test them all there can be more than one.

I use a compression tester instead of a spark plug, either will work.

 

[McCormack]

3.0s are known for wearing out their water pump vanes, so if it were me I would replace the water pump before doing anything else.