Helpppp cooling system problems

[GKERR]

1999 Ford Ranger 3.0 Flex 4x4 Super Cab

I recently replaced my thermostat and radiator cap because i was having an issue losing heat in the cab. The temperature gauge on my truck would warm up and then go to cold and then warm up to "normal" again. I flushed the coolant,radiator and heat. the problem was solved for about a day.

now, the truck will warm up to "normal" and the heat will work fine for about 10 minutes. the temp gauge will then drop to C for about 10 minutes only to rise back to "normal" with the cab heat returning eventually. I have also noticed that the coolant is being stored in the reservoir and not returning to the radiator.

I have filled the truck coolant and burped the system numerous times. The problem keeps reoccurring.

the oil and tranny fluid are both perfect and the truck is not smoking at all.

any ideas or solutions will help!!!

 

[GKERR]

The thermostat i used was not a motorcraft, just some replacement.. Just saying!!! Thanks everyone in advance!!!

 

[enjr44]

I have/had the exact same problem. The tank filling, I fixed with a new cap. I also changed the thermostat and upper hose (probably not needed).

Two things can keep the coolant from returning to the radiator. A bad hose between the overflow outlet on the rad and the overflow tank can cause this. I guess the overflow outlet or the rad or tank could be cracked; but, probably not. Or a bad rad cap. I heard a bit of wisdom the other day. A new part is not necessarily a good part. It is an untested part.

As far as your gauge drifting back and forth. If you figure this out let me know. Mine does the same thing. I believe it could be wires, sending unit or the gauge itself. I just don't see the engine temperature changing that fast and it was doing it before I changed the stat.

Ed

 

[GKERR]

Well hopefully we can figure this out!!!

 

[modelageek]

Did the stat you use have a bleeder.
Mg 2.5 Lima temp gauge would drift when the coolant was low. If I revved the engine the coolant would get flushed over the sensor and the gauge would drift higher. When the system was full and burped it did not happen

 

[GKERR]

Not sure. If that is the hole in it then yes

 

[RonD]

My '94 4.0l had a partially blocked heater core, on this model the heater core is part of the by-pass system so it would cause temp gauge to go high and back to "normal", not overheating just higher and then down, was random as well, going uphill or down hill didn't matter, idle or high RPM didn't matter.
Heat blew warm all the time but never hot.
New heater core($28) and all was well.

If you have a by-pass on the heater hoses in the engine compartment this wouldn't be the issue, but the by-pass valve could be.

Hot and cold heater core usually means air in the system, it forms an air lock in the heater hose so stops flow to core, it will eventually clear, so flow resumes, then reforms if air can not be purged into overflow tank.

This air can come from a leak in the system or cracked overflow hose; when engine cools down it sucks air back in instead of coolant from overflow tank.

Or it can come from a cracked head or leaking head gasket, they start off small, so you won't always see the "white smoke" or bubbling overflow tank.

But higher than normal level in overflow tank can be a sign of cylinder head leak into cooling system.
Cylinder has 600+ psi so a small leak will push exhaust gasses into 16 psi cooling system, so "air" gets pushed in and coolant pushed out, into overflow, raising its level, this air can also stop flow to heater core.

 

[GKERR]

My '94 4.0l had a partially blocked heater core, on this model the heater core is part of the by-pass system so it would cause temp gauge to go high and back to "normal", not overheating just higher and then down, was random as well, going uphill or down hill didn't matter, idle or high RPM didn't matter.
Heat blew warm all the time but never hot.
New heater core($28) and all was well.

If you have a by-pass on the heater hoses in the engine compartment this wouldn't be the issue, but the by-pass valve could be.

Hot and cold heater core usually means air in the system, it forms an air lock in the heater hose so stops flow to core, it will eventually clear, so flow resumes, then reforms if air can not be purged into overflow tank.

This air can come from a leak in the system or cracked overflow hose; when engine cools down it sucks air back in instead of coolant from overflow tank.

Or it can come from a cracked head or leaking head gasket, they start off small, so you won't always see the "white smoke" or bubbling overflow tank.

But higher than normal level in overflow tank can be a sign of cylinder head leak into cooling system.
Cylinder has 600+ psi so a small leak will push exhaust gasses into 16 psi cooling system, so "air" gets pushed in and coolant pushed out, into overflow, raising its level, this air can also stop flow to heater core.

I think im going to run a pressure test this weekend.. I hope its not a head gasket.. The exhaust looks normal, a little smokey but. I have an exhaust it doesnt look like a head gasket...

 

[RonD]

You can always do a Glove Test, quick and easy method to see if there is a cylinder to cooling system leak.

Full overflow and cold heater is often the first sign that type of leak,

If engine has recently been overheated that is what starts the leak, head expands too much from the extra heat and cracks or crushes the head gasket seal.

Hopefully it's just air in the system from bad purge, or a bad by-pass valve.