97 3.0 running hot after Interstate run

[Scoopo]

Hey again all. Been awhile.

I've got a 97 Taurus sedan with something over 100,000 miles.
I bought it from my parents when they got a 2003 model. They bought it with something like 5 or 8 thousand miles on it... so I'm familiar with its history. It has always been well kept.

I don't recall exactly when this 'running hot' problem started but here's the recent history:
I suddenly had a small coolant leak that steadily grew worse and worse. Turned out to be a freeze plug. I had a local shop put a new freeze plug in and all seemed well.
I then had the oil changed and they suggested getting a radiator flush. I remember thinking the shop should have flushed it when they did the freeze plug but you know how it goes... so a few weeks later I had that done and had a new thermostat installed while they were at it.

In retrospect the car has had this odd singing sound that I could never figure out. Very hard to explain but it's a high pitched 'wheezing' or 'singing' that would get higher and quieter till it stopped. That's been happening for a couple of years but without problems. Turns out it's the overflow tank (or whatever it's called) cap.

These days it's gotten bad enough to hear quite often. Like practically all the freakin time.
The main problem is that I have about a 25 minute Interstate commute to work. The temperature is fine on the highway but after running 70-75 mph for a short time the temp guage will climb to just a hair below pegged when I get off the exit.
Yesterday it was hot out. When I went to lunch I got less than 2 miles down the road before the temp was again nearly pegged... after sitting for some 4 hours.

Today I figure I'd top off the coolant after work but it simply wasn't thirsty. I noticed my fans weren't running while the engine was at normal running temperature. After reading here a bit I took it a couple of miles with the a/c on high kind of hoping it was my temperature sending unit (whatever tells the fans to run). When I pulled back in I checked and they're both running as fast as they can. No problem there.

I'm baffled.
Could a bad pressure cap cause this? It does boil over a little even though the temp isn't quite pegged. And it just sings and sings mostly.
Could it be the transmission fluid being too hot to allow the radiator to properly cool the coolant after running at relatively high speed? (wasn't going fast yesterday for less than 2 miles... maye a little further but less than 5 for sure and less than 55mph. And I'm assuming the fluid runs to the radiator for cooling like the old days when I was a parking lot mechanic.)
The tranny has been a little odd for most of its life... kinda acts like it can't decide what gear it wants to be in when in that happy zone between accelerating and decelerating.

Please help!

btw, sorry for the long post. I wanted to give as much info as I could.

[KimMG]

Might be a partially clogged radiator, bad cap, a bad water pump (vanes on pump may be worn).
Check the radiator for cold spots.
Pressure test the cap.

[GPFred]

How about a bad thermostat not opening?

[Scoopo]

I just had a new thermostat installed a few weeks ago while it was in for a radiator flush.

I'm going to put a new cap on the tank.
I'm hoping it's not the water pump or the radiator itself but I don't know just yet. Gotta try the cheap solution first... ie cap. With that thing singing like it's been doing for so long, and having gotten so bad, I'm going to hope that solves it.

It's going to the shop in the morning so we'll soon see. If I can find a cap locally I may not even take it in if that fixes it. *fingers crossed*

Thanks for the replies guys.

[shorod]

Originally Posted by Scoopo

I just had a new thermostat installed a few weeks ago while it was in for a radiator flush.

I'm going to put a new cap on the tank.
I'm hoping it's not the water pump or the radiator itself but I don't know just yet. Gotta try the cheap solution first... ie cap. With that thing singing like it's been doing for so long, and having gotten so bad, I'm going to hope that solves it.

It's going to the shop in the morning so we'll soon see. If I can find a cap locally I may not even take it in if that fixes it. *fingers crossed*

Thanks for the replies guys.

Well, I suppose the shop could have put the thermostat in backwards. Of course, someone would almost have to have been sleeping to do that, but that could explain things if it's been getting worse since the flush.


Also, with the car somewhat cool, remove the radiator cap and start the engine. Watch the coolant for bubbles. If you see bubbles, you likely have a compression getting into the cooling system, either from a bad head gasket, cracked head, or cracked block. I don't believe this is as common on the 3.0L as it is on the 3.8L, but it does happen. This seems like a likely issue since you hear your coolant recovery tank "singing," unless the coolant is just getting SO hot that it is boiling, in which case your thermostat is probably not in backwards.

-Rod

[Scoopo]

Looks like KimMG nailed it with the water pump.

The shop said they could find nothing wrong and couldn't get it to run hot after driving on the Interstate.(figures)
They decided to replace the water pump and afterward said the impeller blades were worn.
After a couple days of testing it out in the heat at 75 miles an hour with the air cranked up, the temp guage has yet to budge above normal.
No singing from the cap either - which was every day whether it registered hot or not.
Yay!

Thanx much for the replies.