Whats the weak link in my cooling system??

90FoxBdy

Founding Member
Jun 17, 2000
553
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17
Linthicum, MD
I finally got the car running after a two year break. My problem is now is that it wants to heat up while driving. At idle it will sit at 190 all day in 105 degree weather. However once you start getting on it it will quickly creep towards the 250 mark. If I back off and drive very easy it cools itself off quickly. My cooling system consist of 3 row pepboys radiator, 180 stat, jegs electric fan pushing 2800cfm with a thermostat switch controlled by a bulb coming in contact with the radiator and a advance auto parts (wp 641) water pump. (I needed standard rotation pump). Stock size pulley

What do you see as the weak link. Is a standard water pump enough to handle my combo? Also is the thermostat switch that came with the fan any good? I really am not a big fan of the concept, but I bought it in a bind.

Thanks for any input.
 
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Since it heats up under load and at speed, the fan should be ok. Total heat rejection could be an issue. Do you think the radiator could be partially clogged or scaled up?

Is the lower air dam in place? A lot of folks on here say it doesn't do much, but they don't live in hot climates. In hot temps, it can help.

Good luck.
 
Have you tried to move the timing any just to see if it helps. look into a High flow water pump, like hissin do you have the lower air dam on it it will make a difference. can you turn on the fan and cool it or do you just have to slow down? turning on the fan would tell me lack of air flow..
 
No i dont have the air deflector. I will try to track one down. There is a good chance the radiator is clogged up in some spots. I have the cleaner running through it now. Have not messed with the timing as of yet. I did have previous problems with heating up from my timing being off but it wasnt like these symptons. The thing would literally heat up within seconds and stay hot.


I know this radiator is not the best but I used it previously with my old setup with hi flow water pump, stock fan, and special service (police) fan clutch and even with a/c in traffic you couldnt get the car hotter than 185. We will see how this cleaner does. Fan blew a fuse so I have to run to the store before i can try anything else.

Thxs for the replies.
 
Do you think the radiator could be partially clogged or scaled up?

I think that's the answer right there as this would be typical when the engine runs hot under load and at speed. Two years without running the engine would be enough for rust and scale deposits to build up and block the radiator.

Is the lower air dam in place? A lot of folks on here say it doesn't do much, but they don't live in hot climates. In hot temps, it can help.

My Stang doesn't have the deflector, I do live in a hot climate (116*F these days), and I don't have any problem with the engine running hotter at speed. If the air dam does help at all its effect must be minor.
 
My Stang doesn't have the deflector, I do live in a hot climate (116*F these days), and I don't have any problem with the engine running hotter at speed. If the air dam does help at all its effect must be minor.

You likely have other cooling system mods to the car that might compensate. If you're not at the low threshold of your t-stat, you might find that while not running hot, you could run cooler with one.

It's also less noticable on a SN95 than a GT Fox (the GT fox has no grill at all. At least SN's have some openings up front).
 
You likely have other cooling system mods to the car that might compensate. If you're not at the low threshold of your t-stat, you might find that while not running hot, you could run cooler with one.

I do have a Mishimoto aluminium radiator and a Mr. Gasket 180* t'stat so they certainly help. The engine tends to stay around 195-200*F now that summer temps. are near 115*F.
My Stang never had an air deflector and none of the other SN95 Stangs that I've seen in the UAE have one either.
 
IMO, don't even bother with that radiator flush crap.
I tried it on my e350 van a few times, it really doesn't do anything to break loose any of the tough sludge.
If you are on a budget take the radiator to a radiator shop and have it cleaned out.
 
If pulling the radiator for the cleaning, something like CLR might clean the rad a bit more than other cleaners that are meant to be added to systems in their dynamic.
 
I just got an awesome 3 row radiator with brass (or plated?) end tanks from CJPony for $126 and free delivery fast. If they have a frequent sale you can get another -10% off that. Holds my 86GT stocker with AOD cooling attached at 180-185 even when autocrossing in 90F+ weather today.

It fit perfectly and came with all the proper fittings and then some.
 
Haven't seen this mentioned, but maybe hose collapse? I've seen that happen.

Also, like previously stated, I would get the air dam put on too.

My 90 GT has a 3 row (S.S.P.) radiator from Autozone, a 180* thermostat, and a flex fan with a spacer and underdrives. It never gets above the "A" in NORMAL, even idling in 100+ degree TX heat.
 
Well I finally got back to it. Put in a borrowed two row radiator. It helped but I'm still having the same probs except now on the highway it wants to stay around 210. Get off the throttle and it will go down to 190 rather quickly. Any more ideas?

TTop I run a standard rotation because of my belt setup. Alt is on the drivers side and I only run crank, wp, and alt.
 
i would just take a look at the hoses quick. if one is collapsing it would restrict the coolant flow. try just runnin it up to 3 or 4 grand and seeing if your hoses are doing anything. i think on my 89 gt the lower hose had a spring in it to keep it from collapsing.