Mark 95 GT convertible

My stock 95 GT convertible is running to the top of the temp gauge. The car sat for many years while I repainted it and moved, about 6 years in total. I changed the thermostat today with a Ford part, and tested it first on the stove to see if it worked, which it did. I let it run about 10 minutes with the air on, and like before, the temp gauge went to the top, and of course I turned the car off. When I did, I noticed that the top hose was not very hot, but the bottom hose was very hot. I'm assuming I have a blockage in the radiator? Is there any other problem, other than that, that would cause these symptoms?

TrimDrip

Did the thermostat have a valve in it to bleed air off?
Was it installed in the 12 o'clock position?
With a cold top hose, I assume you left the rad cap off to let air escape?

Mark 95 GT convertible

I did not see a bleed valve on the housing. If there is one on that car I'm unaware of it. The stat was installed in the proper position, as dictated by the groove in the housing the stat mounts into-it can only go in one way. And, I did not leave the cap off since I didn't add much coolant-maybe a quart or less? Do you think it could just be air in the system? If there is a bleed valve, and you know where it is, please let me know! On other cars I've had before they were pretty obvious, but of course if there is one on this car I've just missed it. Thanks for all the ideas!

TrimDrip

yes, there is a bleed valve after you put it there. Drill a hole in your thermostat and install the thermostat with the bleed hole in the 12 o'clock position. Leave the radiator cap off after starting the car this time and about 4-6 inches of air from the top of the radiator. Otherwise, you will just make a mess when pressure builds.

it's not crucial that you drill a hole in the thermostat but, one day you will understand why I told you to do it.

imp

Some thermostats already have the hole provided. Possibly it was already present; he did not know what your "valve" was, I suspect. Might be a good idea for anyone buying a t-stat to ask for the one WITH the bleed hole. The "air-bound" problem may be exaggerated on SN 95 as the upper hose goes up and over to the radiator, requiring quite a bit of "oomph" to push the juice.


Now, we haven't explained what caused the original overheat. Sure wasn't air-locked. imp

Mark 95 GT convertible

There was a small hole in the factory Ford stat I installed, and it had a tiny pencil lead size piece of metal in it. It was, I assume, used to align the stat with the groove in the stat housing, since the stat is mounted vertically, and keeps it in place while you install it. It is a clever bit of engineering, and the non factory stat I replaced didn't have it. Anyway, how can I tell if what I'm experiencing is just air trapped, and more importantly, how do I get rid of the air? I certainly don't want to buy a new rad if I don't need one.

TrimDrip

oh, well you are good then. Just leave the cap off this time. The air has to go somewhere.

Mark 95 GT convertible

Ok, here is an update. I ran the car about a half our with the cap off. There was air in the system. The radiator bubbled up air several times, and I waited until I could actually see the coolant moving across the top of the radiator before I topped it off. At that time I capped it and let it build pressure. I even drove it a little around my street (no insurance right now, so not too far), and the cooling fan kicked on, even without the a/c on. Unfortunately, it still is running to the top of the temp gauge, it just took a little longer to get there without the air in the system. When I turned it off I touched both upper and lower hoses, and they seemed about the same temperature. I guess I have a blocked radiator? When I bought the thermostat at the Ford dealer the parts guy said he had seen the impeller blades on the water pump dissolve on older cars, and thought that could be a problem too. Any more thoughts? Any way to test a rad to see if it is plugged? NAPA has one for $120. I don't mind spending the money if I need to but I don't want to replace a part unless I know it's bad.

imp

Narrow down the possibilities. Clogged radiator least likely, IMO. Pump a possibility. If you don't mind wasting some coolant, run eng. till hot, thermostat open, have radiator cap OFF, upper hose clamp loosened plenty at radiator, also having manually twisted loose, so the hose may be pulled off the rad. neck.


Shut down eng. allow liquid levels to stabilize maybe 5 minutes. Have someone start eng. while you immediately slip upper hose off rad. neck. Even at idle, pump should be moving a pretty good flow of coolant, perhaps like an average garden hose open at the end. If just a dribble, pump is likely the culprit. If flow prodigious, look into radiator. A radiator shop ought to be able to acid dip, clean it, for much less than the replacement cost.

If you do this, WEAR LEATHER GLOVES, be careful. imp


EDIT: If rad. clogged, pump will draw considerable about of coolant from outlet tank, push it out of top hose, but flow will slow down quickly.

TrimDrip

I have never seen the impeller dissolve on a fox. I have tore down several Tauruses that had that problem but, never a 302 engine pump.


Does the high speed of the fan ever come on? It has to get up to 228 before it does. If you have a temp gun, verify that it is getting that hot and not cooling off.