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Discussion Starter #1
I just got my 1968 cougar on the road again and it has the following mods: 1992 ( I believe) 5.0L short block, gt40p ported heads, vintage shelby 302 intake manifold, hi flow fuel pump, mac headers, cam, and msd ignition. I have not replaced the radiator but I am starting to think I need to.

I replaced the thermostat and filled the coolant back up, but it is running at about 210-250 degrees and climbing @ idle and driving on the street. I immediately parked it and am still trouble shooting. Also the water pump is supposedly brand new according to the guy who built that engine up. Any ideas?
 

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Thermostat have a "dingle" valve or hold drilled in it? May want to check the part numbers on the water pump and make sure that it isn't a reverse rotation water pump. Many of the later 5.0's had a serp setup with reverse rotate water pump. Try running it with the radiator cap off and let it warm up to open the thermostat and see if you are getting good water flow.
 

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Discussion Starter #4
I will try it tomorrow morning but I work nights and the car is across town, I am still trying to get her home !! The engine and trans are newer and other than this temp problem it ran great
 

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Newer 5.0 >'80 are designed to flow the other way - if you had the two pumps off laying side by side you would see that the veins run opposingly....

I'd start by checking that your oil is not showing water signs (marshmellow), and that your hoses are not leaking, etc. It should hold pressure around 14-16 lbs.....if not you need to issolate it. Try swapping cap for new one? Be sure your thermostat is in the right direction! See if your hoses get warm and firm or stay squishy...
 

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Dave,
To check the radiator; run the car to operating temp and then feel across the fins for a cool spot or spots. If it is clogged, you'll feel it. I'm assuming that it used to run OK the way you have it set up.

Don't do this with the engine still running!

Steve
 

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Discussion Starter #7
Here is the deal I forgot to mention it is not serpentine belt driven 5.0 it is spinning the other direction like the old engine so I don't think it is the water pump. Plus the car ran fine until just recently when i found a bad ground was causing a false spike in temp on an aftermarket temp gague. I will try to run it soon and see if it is clogged or not but has anyone bought the Champion or American Eagle brand aluminum radiators ? I am on a tight budget and 250.00 is about my limit for a new one.
 

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I have a Champion in mine, very happy with it. It wasn't direct bolt in like they said, but it may be for you.
 

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If the motor is overheating at idle and slow driving I would suspect not enough airflow through the radiator. Fan OK? Radiator shroud on?
 

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Discussion Starter #10
The fan is new and the shroud is all in tact so I bought an American eagle 1" tubed two core that supposedly cools up to 550hp, I hope to have it tomorrow.
 

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Amen (10 char) ...
 

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I hate to bring this up but you mentioned "the guy who built the motor", I had the same problem on a car a while ago. Trying to diagnose was a bugger but it ended up being "the guy who built the motor" put one of the head gaskets on backwards.....hope it's not but something else to consider....
 

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Here is the deal I forgot to mention it is not serpentine belt driven 5.0 it is spinning the other direction like the old engine so I don't think it is the water pump. Plus the car ran fine until just recently when i found a bad ground was causing a false spike in temp on an aftermarket temp gague. I will try to run it soon and see if it is clogged or not but has anyone bought the Champion or American Eagle brand aluminum radiators ? I am on a tight budget and 250.00 is about my limit for a new one.
If you're running an early 302 water pump with a standard V-belt pulley system, you should be OK.
I'd check the following in this order before spending any money:
1) Make sure ignition timing is advanced correctly (at least 10 deg before TDC on a 5.0L). Retarding timing will cause a late burn and heat up the cylinder walls.
2) Double check to see if the thermostat is installed correctly. Pointy side facing FWD. Copper bulb side facing AFT.
3) Pull radiator cap and watch coolant flow in the top tank. It should be moving pretty fast when up to temp.
 

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Yeah that's another classic one for sure! Easy enough to do -- any luck yet?
 

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Discussion Starter #17
I have determined my timing is way off, need to tune my carb after I adjust timing, and I have a faulty temp gauge sending unit wire or ground connection that will probably suck to diagnose for sure. I just need to get some real downtime to troubleshoot these issues. I have MAC headers and GT40P heads that seem to be contacting with the boots of the plug wires, can that create an emi misfire possibly?
 

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Sounds like it's the guage rather than truely overheating then perhaps.... I'd try to find wires that have a 90 degree plug boot so you can route it away from the headers as much as you can, otherwise it will arc through if it gets thin enough after melting. Timing will play a roll in the engine temps as well, but you need to get that guage working and known good to determine what you have. The sending unit is basically just a resistor that varies with temp it reduces/increase voltage to the guage. There isn't a "ground" other than the case itself and then one at the guage/instrument panel.
 
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