PLS HLP: Overheating on Freeway

[jrnstang]

Guys,

I am stumped at the fact that my car tends to overheat (temp keeps rising) while going 70 on the freeway (Under Load). My car is stock factory with the exception of an Aluminum Rad. My cooling system (Water Pump / Heater Core Bypass/ 180 Degree Therm. / New Upper & Lower Hoses / Stock Plastic Fan w/Working Clutch) has been checked and rechecked. I have also run the car on the freeway without the Thermostat and still overheats (probably not allowing the coolant to cool in the Rad?). I am leaning towards being a clogged Radiator or something clogged in the block, however when I turn the car on and look into the Radiator via where the cap goes, I can see coolant flowing slowly almost dripping thru the core tubes. Also, I do not lose any coolant or get a smell of coolant in the interior or underneath the car.

For example, with a 15 mile stretch (15-20 minutes) of freeway (free flowing) the car (somewhat cool) went from 160 degrees to 260, all this happening while I was going about 70 mph. My temperature is based on an electronic AutoMeter H20 guage I installed in the OEM hole for the stock gauge (Drivers side front on the intake).

Any help or suggestions would be appreciated. Since I have bypassed the heater core (before overheating started), can I still flush the cooling system?

The Radiator is about 6 years old.Sorry,

I also installed a 1993 Cobra Water Pump Pulley (smaller dia.). I do not have underdrive pulleys.

Thanks in advance for any advise.

 

[jrichker]

Under the front bumper there is supposed to be a plastic air dam. It is mounted under the radiator and spans the width of the radiator. Its purpose is to redirect air from under the front bumper up into the radiator.

The plastic air dam is likely to be a victim of parking lot damage or the previous owner’s efforts “to clean up things”. It is needed to maintain proper airflow to the radiator.

 

[jrnstang]

Thanks for the suggestion, I also checked that and it seems to be in pretty good condition (no cracks/Warps). That is another thing I can pretty much elminate from the problem.

 

[93 LX]

bad t-stat?

 

[bhuff30]

You stated a new radiator hoses, but does the new lower hose have a coil inside it to prevent it from colapsing? It is common to suck the hose shut if it does not have a coil inside to keep it open. Obviously, it would tend to suck shut at higher rpms where the water pump is spinning faster. That's probably why you can see water flowing at idle, but then when you get on the highway, it sucks shut.

After getting the car nice and warm, try popping the hood and reving it to 3-4k rpm while watching the lower hose.

 

[jrnstang]

Yeah, I though about that lower rad. hose and replaced it with the one you described, with the coil on the inside.

Thanks.

 

[jrnstang]

Well guys, I had the radiator inspected/cleaned and the shop told me that their was nothing wrong with it. Therfore, I have eliminated the following suspects?



Water Pump

Thermostat

Upper/Lower Radiator Hoses

Temp Sending Unit to Autometer gauge

ECT Switch

Lower air dam infront of Rad.

Clean Radiator

Oli change revealed no coolant

No smell of exhaust in Rad.


Any suggestions?

 

[bhuff30]

How's the ignition and cam timing? You would probably notice a power problem if one of these is significantly off. Excessively retarded ignition timing can certainly cause a cooling problem, as well as cam timing problems.

What kind of rpms are you turning on the highway? My 2.3 had a cooling problem on the highway with a narrow 1 core radiator and 3500-4000rpm on the highway.

If you got an infared temperature gun, you would figure out better what's going on. Then, you would check the temperature of the upper and lower hoses to see if you are cooling well (with fan on), and if your T-stat is really opening up.

 

[Bullitt95]

An engine that only runs hot on the highway under load and runs cool the rest of the time can only be due to one of the following:

Clogged radiator
Lean A/F mixture (clogged injectors, clogged fuel filter)
Retarded ignition timing

If the temp. gauge intermittently spikes high at other times, you could have a sticking thermostat.
Even with the underside air deflector removed, the engine shouldn't overheat on the highway.

 

[jrnstang]

Actually, I noticed that the coolant was really not flowing once the thermostat (180 degree) opened and I did a power flush of the water jackets. I think that did the trick. Took her for a test drive (20 minutes) and never got over 200.



I want to thank everyone for their comments and suggestions. I appreciate guys taken time out of their lives to help out a fellow mustanger.



Thanks again,