Engine experts please come in...

[Gears & Crosses]

OK, heres the story. I have an 86 SVO Mustang with a 87 5.0 motor installed. This car has been sitting in retirement for about two years and I am ready to get this car back on street duty. The problem is, before I put the car up, it would run hot. The real problem is it would only run hot when running on the highway, not sitting at idle or cruising around town!!! When on the highway the temperature gauge would come up and the engine would ping. I have never heard of a car only running hot on the highway. The engine sounds and runs fine otherwise. What is wrong????

Let me give you some more information. Before the trouble started I changed the water pump, put on 1.7 roller rockers and I changed the timing chain. The car did not run hot before these changes. The car has a relatively new 3 core Modine radiator, 180 deg. high flow themstat, stock clutch fan and shroud.

If I remember correctly I tried playing with thermostats and that did not help. I just took the water pump off this weekend to see if they gave me the wrong water pump but it matches my old water pump (checked the impeller).
My next guess is that the lower radiator hose is collapsing?? I don't know.
Please help me this 5.0 get back on its feet

Gears

 

[ss93cobra]

Probably a dumb question, but you did "burp" the system to evacuate any air pockets and then rev the throttle and dump in as much coolant as you possibly could right? The radiator hose being suspect isn't too likely really. Some aftermarket brands of thermostats aren't worth a darn either. What type did you install? With a 3 row radiator and 180 degree t-stat my car barely climbs over 180 before the stat opens up and cools it down. For whatever reason your problem is more related to extended higher rpm's which makes me wonder about the cooling system having air pockets in it. Let me know and good luck.

 

[mustangkid5]

have you checked timing? not only dist but cam timing too. motor can make extra heat if the timing is to far advanced. just and idea.
5.0 used revers rotation water pump so if you changed waterpumps and started over heating maybe got wrong one.
I dont know if the block or heads have been switched but ford used different coolent passages in 60's 70's and 80's head gaskets will interchange from all years but not the head to block. A friend of mine had same problem and motor had been rebuild and the used 70's model heads on a 80's model block.
I would try to burp the radiator park car with the radiator higher the motor (on a hill or use a jack and some stands to lift front)
Just trying to give a couple ideas

 

[bmo37]

i would guess since your having over ehating problems when high speed driving either the stock clutch fan or the fan itself is the problem, if the fan doesn't slow down and let the air moving through the radiator cool it will cause a problem.

I'd do the fan clutch and maybe a flexlite fan.

 

[Mustang5L5]

Maybe it's trying to tell you it wants the 2.3L turbo back

 

[schiccc]

i had the same problem , i switched out the fan clutch and no more over heating on the highway

 

[88stangmangt]

lol no more 5.0 i want my turbo back lol

 

[SmockDoiley]

Usually if the car is overheating at idle its the water pump or fan. If its overheating at speed, its the radiator. How does that thing look? If its the original radiator, not only is it really old, but its also probably too small for the 5.0. Let me know how it looks.

 

[jerry beach]

Usually if the car is overheating at idle its the water pump or fan. If its overheating at speed, its the radiator. How does that thing look? If its the original radiator, not only is it really old, but its also probably too small for the 5.0. Let me know how it looks.

This is true, The hose may be sucking shut at hwy speed. Squeeze it and see if there is a spring inside to hold it open. If not I would put one in to be sure. You could rev the motor and watch it to see if it sucks shut, just stay out of line with that fan. Is there scale in the rad from sitting? Heat it up at home with the cap open and look for good flow in the rad. The only other thing I can think of would be the stat stuck open and letting the water flow too quickly at hwy speed, not giving it enough time to cool in the rad.

 

[Gears & Crosses]

Thanks for all of the responses,

ss93Cobra - I am sure that I probably didn't burp the system, but I have one of those vent/lever release caps that I opened a few times to check the level in the radiator. Would this venting be considered good enough? When I refill the cooling sytem this time, I will do as you and Mustangkid suggested. The thermostat is a Robert Shaw/Motorcraft type.

Mustangkid5- I have checked the timing and I even retarted my timing back to the base 10 degrees advanced. My worst fear is that the cam timing could be off, even though I was very careful when i installed the timing chain. I really don't want to tear it down to the timing chain again. Do you know of a way I could check the cam timing without tearing it down??? I thought of the reverse rotation water pump and I thought for sure thats what the problem was going to be. I just tore apart the water pump and compared it to the old one I had. They have the same impeller.

bmo37- The stock fan clutch is the original one with the engine. Maybe its time for a new one.

schiccc- Thanks for the feed back I will try that if the cooling system burping and new radiator hose don't work.

SmockDoiley - No, I don't believe its the radiator at this point. It has very few miles on it and it was purchased new a few years ago. It was only about a year old when I first had this problem. It is a new Modine 3 core HD radiator.

jerry beach - You are thinking what I am thinking. Do our lower radiator hoses come with a spring in them? Does anyone know? I am going to check for one on mine. I hope thats the problem. I might just change out the thermostat anyway just to be safe.

I will probably start working on it tomorrow guys. Thanks for all of your ideas!

Gears

 

[Gears & Crosses]

It has been verified that there in not a spring in the lower radiator hose. Can anyone verify for sure that there is supposed to be a spring in the lower hose.

Thanks

 

[Gears & Crosses]

TTT

 

[Mustang5L5]

I have no spring in mine

 

[bmo37]

never heard of a spring in a radiator hose, i know none of my many stangs ever had that.

 

[79'293stang]

mine has a spring in it but it wasnt the stock peice it was one i bought from a parts store

 

[white 89 GT]

Is the fan turning the correct direction.

 

[Gears & Crosses]

I just went to Advance Auto and they didn't have a spring in a new hose. I may try somewhere else tomorrow.

white 89 GT- Thats a good point. I will check the fan rotation / serpentine belt routing when I get the car back together. I am going to put it together with a new lower radiator hose and a new themostat and burp the system and go from there. The fan clutch will be next.

Thanks again,
Gears

 

[Mike86Stang]

I have a spring in mine to prevent it from collapsing, if it helps.

I also believe that this may be the fan clutch going /being bad.

As a side note with the whole directional thing with the water pumps
& fan thing. Just make sure your belt is routed right other wise you
could possibly be spinning it in the wrong direction.

 

[Mustang5L5]

How much resitance does the fan clutch have? If it spins relatively freely then it's most likely bad. It should spin with resistance when you turn it by hand

 

[Mike86Stang]

How much resitance does the fan clutch have? If it spins relatively freely then it's most likely bad. It should spin with resistance when you turn it by hand

Just to add on to what Mustang5L5 said....it shouldn't hardly spin at all... if you try to spin it ...it should move maybe an additional 3-5 inches of rotation & then stop if that much.