[Bullitt95]

Today I tried the manual high speed fan switch for the first time. The fan works fine but even on high speed, the engine still runs hot (gauge on A, sometimes on L) with the AC running whether I'm idling at a stoplight or barrelling down the highway at 80mph. It's 113*F outside. That rules out the fan as a problem.
I've come to the conclusion that the stock radiator simply doesn't cut the mustard when the outside temp. goes above 95*F, so I'm going to order a Mishimoto unit after payday.

[burnout5.0]

yeah but i have also heard that ppl put an aftermarket radiator in too and that still doesnt fix the problem so idk... im gonna try a new radiator too but i might not fix the problem from what ive heard

[07gtmustang]

you could have a leaking head gasket you might want to get an internal block leak test also how old is the coolant is it dirty is it at the right protection level all could have be factors or one

[07gtmustang]

and is it at the proper level

[07gtmustang]

had a 94 gt 5-speed but did not have this problem, 3.8 are known for blown head gaskets not sure on the 5.0

[Bullitt95]

Originally Posted by 07gtmustang you could have a leaking head gasket you might want to get an internal block leak test also how old is the coolant is it dirty is it at the right protection level all could have be factors or one

I already had the head gaskets replaced less than two weeks ago (I did have one blown gasket on no.1 cylinder but that was caused by a stuck t-stat). Now I'm not losing coolant anymore and the system holds pressure, but the engine still runs hot with the AC on and the engine's without a t-stat. When the AC is off, the gauge doesn't go higher than M (208*F) which is acceptable for me in 110+*F weather. The coolant is new, as you would expect with new head gaskets.
I flushed the cooling system a couple of months ago and even tried leaving vinegar in it for a couple of days. Not much dirt came out; the system was clean.
I think it's time to change the radiator anyway 'cause it's 12 years old. A new aluminium radiator might just make a difference.

[07gtmustang]

if it is holding prussere I would think that it would being do the job I'm sure you've checked to make sure there isn't an air pocket tell us what happens

[Bullitt95]

No air pockets as far as I can tell. Usually an air pocket gives itself away by the gauge fluctuating wildly but mine doesn't do that.
There's one more thing I'll try before I order a new radiator. Since I don't have a t-stat, it's just possible that the coolant is flowing too quickly through the radiator to reject enough heat, so I'll insert a restrictor inside the upper radiator hose. It'll narrow the orifice to the same 1" diameter as the opening in a t-stat and hopefully by slowing down the coolant flow through the radiator, it'll reject more heat.
It'll be trial and error so I hope it won't be error.

[black95conv]

Why dont you just put a thermostat in it. It had one in it from the factory. That way you know there won't be any error and you can rule out "Lack Of Thermostat" as a possible problem.

[Bullitt95]

I tried that about three ago. I bought a brand new Motorcraft 192* t-stat believing it to be good and I installed it. First drive out after about 3 minutes the gauge suddenly swung from the O of NORMAL and pegged into the red. I nursed the car back home after letting the engine cool a bit but I had to pull over and shut down the engine again when the gauge pegged for a second time. I later removed the t-stat to test it in a pan of boiling water. The F&#$ing thing was sticking closed, and that's what caused my head gasket to leak. That's why I didn't put another t-stat back in. After that, the gauge never pegged again but the engine just ran hot as normal. Unfortunately the coolant level in the overflow reservoir would drop and I saw the occasional puff of white smoke from the passenger side tailpipe, and that's what led me to suspect the head gasket had blown. Pulled out the no.1 spark plug and sure enough, coolant started coming out of the plug hole.
I'm going to order a 180* t-stat online and hopefully that one will behave itself. In the meantime I'll try my restrictor and see how that works.

[95blackbeauty]

Its the freakin fan. there was a recall on our year model fans. if u buy a stock replacement its like 200 bucks and u will run coooolllld fo sho.

[Euroeater95]

I dont think that buying a new stock fan will fix the problem. I read the fan recall and it said that there is a chance that the fan bearing could seize and cause an underhood fire. It didnt say anything about the fan not working properly in high or low speeds.

[Euroeater95]

I am also having temp issues and I was thinking of trying a regular fan like the 87-93 Mustangs have. That way it cant be a fan problem anymore, since the fan spins as fast as the engine.

[Bullitt95]

Well, the restrictor in the upper radiator hose had no effect whatsoever. My Mr. Gasket 180* t'stat arrived in the mail yesterday so I'm going to install it tomorrow. I remembered to test it this time in a pan of hot water and it opens/closes properly (unlike the new OEM t'stat I had earlier), so I'll see if that helps at all. I'm not expecting much but I'll be happy if the gauge doesn't go higher than A (215*F) when I have the AC on, so at least I won't have to keep switching the AC off to keep the engine cool and be sweating like a pig behind the wheel.

[95blackbeauty]

ok i couldnt drive my car like five feet without it over heating...the reason being because my fan didnt engage at the right speed at the right time. I know for a fact that a stock replacement works because that what i did. Now if your fan is in working order then im sorry for the suggestion. But by replacing the fan and wiring a switch to the highspeed allowing you to turn it on high at the click of a button....heat problems (for me at least) went out the window.

[Euroeater95]

Wait man, I wasnt calling you out. All I was saying that my problem isnt due to the fan recall, which has nothing to do with with the speeds not working properly. I wasnt saying that you were wrong and I am sorry if it sounded like I was. I am just trying to reason out the problem.

[95blackbeauty]

ah no problem dude. im sorry if i snapped but it totally fixed my heat problem.

[Bullitt95]

Now that I've driven my Stang a few miles with the Mr. Gasket 180* t'stat in place, I can safely say that it's made no difference whatsoever. My engine still runs at 212*F (between M and A) with the AC off and at 222*F (L) with the AC on while driving on the highway. Having the high speed fan on all the time made no difference either.
I've already flushed my cooling system twice so I think the only thing left for me is to replace the radiator. Since I have a 3.73 r&p instead of the stock 2.73, the engine rpm in overdrive is 36% higher and I think the extra heat produced by the engine is too much for the stock radiator to cope with.