My '88 5.0L Sport is still running warm....I broiled out the rad w/ a vinegar mix and changed the thermostat.
When rolling along it will run ok on the temp gauge then the needle will go right up against the top of the normal bracket for a little while then drop back down to the middle. Last week it ran at the top long enough that the front tranny seal started leaking. It did not help that the wife was racing a punk and gave the 'bird a flogging! When it sat and cooled back down the seal stopped leaking.
So...the rad was flushed and thermostat was changed and the problem still exists. What to do next??
Is the fan and fan clutch in good shape (assuming stock stuff here)? Maybe there is air in the cooling system somewhere?
Darren
Are you sure it's not the gauge? When the temp gauge pops up, do the fuel and oil pressure gauges also increase?
Maybe a bad sending unit or broken wire?
Darren
The gauges do not move together...been watching them close. The fan appears to be in goood shape.
......and how would I get the pocket of air out?
One trick is to drill an 1/8" hole at the top of the thermostat in the lip. This allow it to burp past the thermostat but not flood past during normal operating conditions so the thermostat actually works. I drill it and then do this to hold it in the 12 o'clock position:
(http://i786.photobucket.com/albums/yy142/dbrune_83/Thermostat1a.jpg) (http://i786.photobucket.com/albums/yy142/dbrune_83/Thermostat2a.jpg)
Darren
Or just leave the cap off and run it till it burps off, Your thermostat seems to be working, it raises the temp and when it opens the temp drops. If your rad. is in poor shape it may still be clogged. If you know for sure your fans working. and it heats up at a sit still It probably is your rad. It wouldn't be by chance it's full of debris in the front of it between the ac condenser and the rad?
I reread the original post and I think you are on to something Kitz Kat. I read the boiling out part but what about the radiator getting rodded (mechanically cleaned)?
Darren
For the price, you can get a new stock one for less than 100.
You can narrow it down by the way the symptoms appear. Does the car run hot at highway speed but fine around town? That would be a rad issue. Is it hot in town but fine on the highway? That's a symptom of a slipping fan clutch.
Also, do you have a TC nose on the car? If so, the black plastic chin spoiler is a MUST. Even without the TC snoot you should have the black plastic piece there. These cars are bottom feeders (most of the cooling air comes in from under the bumper).
It will run hot randomly at both highway and city speeds.
Nothing is packed up between the A/C condenser and radiator.
When I filled it up with water/antifreeze, I did leave the cap off until it reached temp and it bubbled out air then topped off.
It has the factory sport nose and chin spoiler in place.
Sounds like you did it right to me. I had one motor that just did not want to burp the air and it took several attempts. I think I finally removed the temp sending unit and it made a small mess but that finally got it fixed. I think the hole in the thermostat would have done the same thing but I was young and had to battle stuff back then.
I know pulling the radiator is a pain but most good shops will test it for you and give you a quote on what it would cost to rod it. If its a factory piece then I am with Kitz Kat on you would save yourself a ton of hassle by buying a new one and just swapping them out. I got my 3 core for both my cars cheaper online than at the parts stores here:
http://www.npdcool.com/radiator/index.php/cPath/21_396
Hope you get it figured out as this problem is right up there with diagnosing fuel/ignition issues.
Darren
Rads are easy......much better than tranny's!!
It's got to be either a radiator or fan clutch issue. I'm leaning towards the radiator if it gets hot at highway speeds. Can you see the fluid move through the radiator with the cap off?
Just a shot in the dark but how old is the water pump?
Did you get that dry erase board yet? Kidding of course.
Darren
For burping purposes I usually undo one of the throttle body hoses while filling up the radiator, in conjunction with a couple tiny holes in the thermostat, 180 deg. apart from each other. After that, whatever small bit of air may be left evacuates without issues. I just make sure the rad overflow is full, and let it do its job.