over heating help needed

[truetriplex 1]

I need some help with an overheating issue that I am having. I have a 69 R code Mach that is driving me crazy. Car is all original with automatic transmission and air-conditioning. Less than 50 miles on the rebuilt motor, and the radiator and cooling system were completely gone through. It has a 160 thermostat and is running the factory stock carb.

It has been very hot here in Georgia, and normal street driving sees my engine temperature running around 180-190 mark, per the dash thermostat. Within 15 seconds of turning on the air conditioning, the temperature climbs up near the 220 zone, per the dash thermostat. Needless to say, I shut it off before it gets too hot. I have used a heat gun to check the radiator and thermostat housing temperatures.

Normal running condition has heat gun readings around the 180 – 190 range. Again, when I throw in the AC switch, the radiator and thermostat housing readings quickly hit to 220°. I will be checking the jets on the carb later in case the previous owner had changed them out. I have already checked the timing and it is perfect. Does anyone have any thoughts or suggestions?
 

[Brian Conway 264]

Let me suggest that you don,t touch anything concerning the motor or carb.  Does your car have the bi-pass valve that omits your heater core/circut when the AC is turned on ?  Brian

[ray1970 88]

I know you say the cooling has been ck out but the radiator my not be up to the task at hand.

[Caseyrhe 650]

Same ideal on heater by-pass. Did the thermostat you put in have the small bypass hole in it?

[Dave R. 85]

 Do you have the correct fan? My 1969 R code is a 4 speed and of course non-air but a similar problem when stopped in traffic in 80*+ temp. I had a 6 blade fan instead of the correct 7 blade. Also the correct shroud and fan clutch are important. My aftermarket temp sender also contributed to incorrect gauge reading. Made a big difference.   Dave R.

[Dave R. 85]

Here is an interesting article that I had to search for in my bookmarks.   Dave R.

 

http://www.automotiveu.com/SolvingOverheating.htm

[barnett468 418]

I have already checked the timing and it is perfect.

 

 

 

no its not if you have not set the timing curve.

 

you need a 180 t stat.

 

need to know exactly what fan you have and if you have a shroud and if your fan clutch is worn if you have one and what your compression is and how far the engine is bored out and if you have a 2 or 3 row radiator.

 

you most likely need a bigger rad and better fan.

[truetriplex 1]

no its not if you have not set the timing curve.

 

you need a 180 t stat.

 

need to know exactly what fan you have and if you have a shroud and if your fan clutch is worn if you have one and what your compression is and how far the engine is bored out and if you have a 2 or 3 row radiator.

 

you most likely need a bigger rad and better fan.

I DO have the correct fan and fan clutch and shroud. The radiator is factory correct for an A/C car and was professionally cleaned and gone through by a shop that specializes in this work. I will have to check on the bi-pass from the heater core

[barnett468 418]

I DO have the correct fan and fan clutch and shroud. The radiator is factory correct for an A/C car and was professionally cleaned and gone through by a shop that specializes in this work. I will have to check on the bi-pass from the heater core

 

heater core switch has nothing to do with the car overheating.

 

you did not answer my other questions.

 

like i said, you probably need a bigger rad and better fan but need to properly set your timing curve first.

 

if you can spin your fan and it rotates freely by itself  more than one turn, it is weak.

[truetriplex 1]

after the engine was machined and gone through COMPLETELY, it was running a 10.5 compression ratio.  Fan does not spin freely (there is resistance) and it does have the factory 7 blade fan. bore was .030 over and it is a 3 core radiator - freshly re-cored also.  I only wanted to do this motor one time so I tried to have the best professional engine builder do it right. FYI, the distributor was recurved and set to specs.  EVERYTHING in the motor is new, rebuilt, restored or machined to specs

[1969_Mach1 333]

I agree with bernett468, the radiator is very likely not up to the task.  Also, make certain your fan clutch is okay.  Maybe swap it out for a new thermostatic fan clutch and don't opt for the least expensive fan clutch.  With those, you get what you pay for.

 

Cooling systems were marginal at best for cars of this era.  Overheating issues do not surprise me.  I've mentioned it many times, as a kid seeing cars overheated on the side of the road during hot summer days was a common occurrence back in the 1970's.

 

Plus new motors run hotter due to increased friction and cylinder pressures.  Boring 0.030" can also contribute to higher operating temperatures.  Good luck.  There is a lot of heat packed into a small engine compartment with very little way for it to escape.

[ray1970 88]

I agree with bernett468, the radiator is very likely not up to the task.

 

+2 Things have changed over the last 40 years... Radiators have got a lot better.

In the 70s over heating was normal..No need for it nowadays..

[Max Power 74]

Agree on the radiator as well. ACP makes affordable direct replacement ones. No mods necessary.

[danno 128]

One simple test is to find out if it overheats when driving at 70mph.  Take it on a drive for  15 minutes at this speed, and if it still gets hot, you can rule out all the fan ideas.  That only then leaves either the engine creating too much heat, the water in it not flowing,  or radiator too small. My guess is you already know this.  I am interested to see what you find and will keep following.  Good luck these issues are frustrating.

[barnett468 418]

after the engine was machined and gone through COMPLETELY, it was running a 10.5 compression ratio.  Fan does not spin freely (there is resistance) and it does have the factory 7 blade fan. bore was .030 over and it is a 3 core radiator - freshly re-cored also.  I only wanted to do this motor one time so I tried to have the best professional engine builder do it right. FYI, the distributor was recurved and set to specs.  EVERYTHING in the motor is new, rebuilt, restored or machined to specs

 

Your distributor is likely not perfectly correct but it may not be far enough off to male a difference but only testing will tell . Buy a bigger rad and/or better fan or fixed blade fan and a high flow 180 or 190  stat and be done with it.

[truetriplex 1]

I do wish to thank everyone for the valuable input.  I too agree that the problem may stem in teh radiator.  I have taken the car on extended drives (both freeway and city) and even at cruise, the temperature guage stay near the high side, but still in the safe range.  But my question remains unanswered as to why, at curise at 60 MPH's, within 20 seconds after turning on the A/C my temperature gauge will spike to full blown hot.  And this is an actual 20 seconds of time.

 

I happen to be a purist and keep my cars at, or near a 100 point level of restoration.  This is why I will spend the extra money to have an original radiator re-cored, or internally modified (additional core added) to achieve my goals of keeping my cars authentic. Is there a radiator out there that someone can recommend that will accomplish both goals?

[jmlay 80]

The AC condenser sits in front of the radiator. With the AC on the AC condenser heat is transferred from the condenser to the air as air moves through. This same air, heated air, is passing through the radiator. Simply the extra heat/load from the AC condenser may be pushing the cooling system over the edge. 

[Dave R. 85]

truetriplex, do you have the correct pulley on the water pump? A pulley that is larger in diameter slows the pump.   Dave R.

[barnett468 418]

the compressor also requires more power to turn which creates more heat in the engine.

 

the condenser can get to 160 degrees so you are suddenly running 160 degree air into the front of your rad soon after you turn the ac on.

[LoneWolf2U 136]

Change the stat to a 180 degree and slow the coolant flow down. A 160 will be fully open at all times not allowing your rad to do its job correctly.

[lanky 44]

Like a few have said you are definitely running the incorrect temperature thermostat. I bet without the AC on this would make your car's  running temperature be even better, however I also tend to think with 10.5 compression and AC that your radiator isn't up to task.

[truetriplex 1]

Okay, it appears a new symptom has just cropped up. I was checking out the dash control panel when I observed the following. The car had been running for nearly 20 minutes and was at a stable operating temperature. I switched on the fan blower only. The AC was not on (clutch was not engaged on the compressor) nor was the heater switch set too high or hot. Immediately, when the fan blower motor engaged, the temperature gauge immediately went up. When I shut the blower motor off, the temperature gauge returned to its previous position. I am now beginning to suspect that there may be an electrical problem, but I don’t know why. Does anyone have any suggestions?

[LoneWolf2U 136]

missing or poor body grounds. your temp sending uint is taking the ground load.

[Dave R. 85]

+1 on Mach 1 Rider's comment at least as a starting point. Sounds like it has to be an electrical problem not a heat problem.   Dave R.

[Caseyrhe 650]

Shocking that 23 post later its an electrical issue