Heating and Engine Operating Temp Issues

[horse with no name]

Hi All,

I have a question that likely has been asked before, however, I couldn't find any threads that detail my exact issue. I have an '88 5.0 with minor mods (Exhaust, Gears, Short-throw shifter, Fluidyne Aluminum Radiator).

Recently I have began to notice the temperature fluctuating between 160° and 200° after the car has warmed up. The engine temp even occasionally dips back down to about 140° after approaching 200°. In addtion, the heater takes forever to work(about 20-30 minutes), and even when it does, it occasionally begins to blow cold while the engine temperature continues to fluctuate.

Initially I was thinking this was maybe a thermostat issue. However, I am concerned the heater core maybe beginning to go out (no signs of leakage though). Haven't changed the thermostat yet.

Any thoughts?

Thanks in advance for your help!

[horse with no name]

All,

Just an update on my post from yesterday --- Upon getting home yesterday after my commute, I noticed a faint scent of ethylene glycol as I was walking past the front of my mustang, and noticed steam coming out of the hood...

Upon further invesitgation I discovered that my $400 Fluidyne Aluminum radiator was leaking on the back left hand side, right near a weld line (Only about 4 years old, maybe has 6000 miles on it).

Not sure if this is a common occurence for Fluidyne radiators? Has anyone else had this happen to them? Any one have any issues with any other Aluminum radiators?

[buckneked7719]

my car does the exact same thing it has the stock radiator.it doesnt seem to leak.but it takes forever to warm up.and the heater doesnt seem to get that hot even at full operating temp.i also notice the fluctuating temp.i was also thinking of replacing the thermostat.i also noticed what appears to be a vacume operated valve inline on the heater hose.t hink it might control the flow to the heater core im going to try that as well .if you find a solution to your problem please post. im tired of freezing to death any help would be appreciated

[horse with no name]

Update # 2- On the heater/engine temp fiasco on my 1988 5.0 - Spent Super Bowl Weekend replacing the radiator, bi-pass hose, serpentine belt, thermostat, and thermostat gasket.

Result: Heater performance not much better, and now the temperature gauge doesn't work at all.

Help -- Any ideas/suggestions would be appreciated -- I am guessing the heater core is to blame, but no signs or smells indicating leakage --

[USMC302]

What temp therm are you using and did you let all the air out of the system after the install? Did you drill a very small hole on top of the thermostat before installing?

[horse with no name]

I replaced the old Thermostat with another stock unit (195 degree). I did not drill a small hole, should I have? Also,the temp gauge is working, but the car is not getting above 150 degrees, which is okay, I guess.

The heater performance is okay, but it does not blow as hot as it use to.. I am wondering if the heater core is source of all the problems...

Thoughts?

[USMC302]

The small hole helps. You temps should be getting more than 150 unless it's -5 outside. It should warm up to 180 at least for an optimal running temp.