Overcooling/overheating & no heat! HALP!

[skwerlgurl]

My reliable 13yr old Mustang (175K miles) has been acting weird in regards to heating/overcooling/overheating...particularly when the temperature drops below 30 degrees F.
Recently there has been little to no heat, all the while the engine temperature stays low, then rapidly jumps to near overheating. Most of the time it will level out to normal operating temperature, and heat returns to the passenger compartment.
When this started 2 weeks ago, I had the thermostat replaced & had the system flushed- didn't help.
Then I replaced the water pump (it was the original, god bless it lasted 175k/mi) the fix lasted all of 6 hrs.
The fan appears to be working properly. I have monitored the coolant levels- there is no loss, and I have not had to add any. The head gasket is ok (having replaced the defective one 50k ago) and there is no exhaust gases in the coolant.
My mechanic and I are running out of ideas.
Have any fellow 3.8L mustang owners out there had a similar experience?
I think the old pony still has some good years left.
The stench of burnt antifreeze haunts my dreams & stings my nostrils

 

[Lsredy2kstang]

Did he properly "burp the system". There is a procedure that you have to follow closely to do it properly.

 

[skwerlgurl]

Did he properly "burp the system". There is a procedure that you have to follow closely to do it properly.

Yes, Fred was "burped". I'll shall find out more later.

 

[Skymarshal]

You said the mech said this was not a blown head gasket, but it sure sounds like it. Did he check again for that? Have him put shop air into each cylinder of the warm engine while the piston is at TDC and check in the radiator for bubbles.

 

[skwerlgurl]

You said the mech said this was not a blown head gasket, but it sure sounds like it. Did he check again for that? Have him put shop air into each cylinder of the warm engine while the piston is at TDC and check in the radiator for bubbles.

Not the headgasket- that was the 1st thing he checked...especially since my year/eng size had the defective head gasket trouble. (Took care of that right away)
Believe it or not, it was the stock radiator! There was a tiny pinhole leak & 13yrs/175k miles worth of crud & foulness clogging it.

This car just keeps going and going- truly Ford tough.

 

[GTA_V6_Mustang]

Still love to hear about those 94-95 3.8's that just wont die. Thats how my stang was, Just couldnt kill it.

 

[skwerlgurl]

Still love to hear about those 94-95 3.8's that just wont die. Thats how my stang was, Just couldnt kill it.

My lil pony has been fed a steady diet of cheap gas, infrequent oil changes, many, many sets of tires, bad mechanics, has been driven thru the very bowels of hell and was hit in the rear by an old lady in a buick roadmaster- i had a tiny smudge of her paint. She had 2000 worth of front bumper repair.
Whoever says Ford can't make a reliable (and awesome) car should be dragged behind their communist Honda Civic hybrid.

 

[RED2001GT]

My lil pony has been fed a steady diet of cheap gas, infrequent oil changes, many, many sets of tires, bad mechanics, has been driven thru the very bowels of hell and was hit in the rear by an old lady in a buick roadmaster- i had a tiny smudge of her paint. She had 2000 worth of front bumper repair.
Whoever says Ford can't make a reliable (and awesome) car should be dragged behind their communist Honda Civic hybrid.

It's really very nice to read something like this about the V6 Mustang. I also own a V6 Mustang which has seen 5 years of salty roads and a repaired front bumper and a repainted rear bumper from a hit and run. It's got 39,000 original miles on it so far. I'm hoping that my little pony will last for many more years to come and that I will be able to put 400,000+ miles on it without having to do any major repairs on this car.

 

[RED2001GT]

My lil pony has been fed a steady diet of cheap gas, infrequent oil changes, many, many sets of tires, bad mechanics, has been driven thru the very bowels of hell and was hit in the rear by an old lady in a buick roadmaster- i had a tiny smudge of her paint. She had 2000 worth of front bumper repair.
Whoever says Ford can't make a reliable (and awesome) car should be dragged behind their communist Honda Civic hybrid.

It's really very nice to read something like this about the V6 Mustang. I also own a V6 Mustang. It's a 2002 Mustang which has seen 5 winters of salty roads and a repaired front bumper from a hit and run and a repainted rear bumper. It's got 39,000 original miles on it so far. I'm hoping that my little pony will last for many more years to come and that I will be able to put 400,000+ miles on it without having to do any major repairs on this car. It would be nice for everything to stay original on my Mustang without anything breaking down.

 

[skwerlgurl]

It's really very nice to read something like this about the V6 Mustang. I also own a V6 Mustang. It's a 2002 Mustang which has seen 5 winters of salty roads and a repaired front bumper from a hit and run and a repainted rear bumper. It's got 39,000 original miles on it so far. I'm hoping that my little pony will last for many more years to come and that I will be able to put 400,000+ miles on it without having to do any major repairs on this car. It would be nice for everything to stay original on my Mustang without anything breaking down.

Oh, and I hit a deer too- no damage...at all. weird!

It is a great car...but the wacky heating thing continues. I have found my car consists of trial and error repairs. I haven't had to do major repairs, but troubleshooting to find the problem is maddening.
Currently with this issue with no heat/overcooling/heating I have:
Powerflushed radiator
New thermostat
replace original water pump (even if not the cause, HAD to be replaced)
replace original radiator (same thing)

I am running out of things to replace. It may the headgasket mad: ) or the fan relays...but that is only a guess.

Otherwise- this car is the penultimate survivor, and I love my car.

(if it is the headgasket, anyone got a clue on how much that will run?)


***update****
Finally, it did the weird fan thing while the mechanic was driving....the saga is drawing to a close!