Idle temperature with rebuilt head

A

ags290

Well-known member
Supporter 2022
Supporter 2021
Supporter 2019
Howdy ,

I was setting the timing on the 170 this morning after installing the new head and noticed the temperature starting to climb. The heater hoses were warm to the touch after about 10 minutes at idle. The upper radiator hose was cold, so I grabbed my infrared temp gun and checked them. The heater hoses registered 185 on the inlet and outlet and the upper radiator hose was ambient temperature 70 degrees. I checked the temperature sending unit and it registered 200. I then checked the factory gauge and it was almost to the full hot so I turned the car off and am letting it cool down.

The head I originally had on the car was a C4DE and I replaced it with a C7DE, so the temperature sending units were different sized. I switched over to a sending unit for a 1968 mustang to fit the hole. Will this be compatible with my 1965 gauge cluster? Also , when I ran the car yesterday it never got above the half point on the gauge but the radiator cap was off the entire time as I was trying to purge air from the system. Could I have an air bubble still trapped in the system? Are these cars susceptible to that? It's there a trick to burp the coolant system?

I ran it yesterday with the radiator cap off and waited for the radiator coolant level to drop and then filled it with water and ran it until I saw good coolant flow through the radiator. Am I worrying about nothing?

Kevin

PS I have not had any overheating issues before with the car, even in the Texas Summer.
 
I think its air Kevin. Not sure how many times you have run and filled since you got it back together but when I did mine I drilled a very small hole in the top (up) side of the thermostat flange to help with the fill when it's closed. At least I think that's why I did it, there may have been beer involved!
 
When the air eventually comes up to the top, it creates a void in the pump and nothing circulates and you see nothing coming through the top hose. You will have to refill a couple times to purge all the air.

Run with the cap off when the block is cold and you will see the coolant level drop quickly when the t-stat opens. Let it run for a while: 10 minutes or so refilling as needed. You will see air bubble out and then gradually quit bubbling. It takes a little while for all the high spots in the block to purge. Do it a couple times over the week.

After all the air is purged, make sure there is about a 1/2" of air at the top of the radiator. No more.
 
I wouldn't think there would be much of a differance between those years of temp gauge senders but if you have a Volt / Ohm tester measure the resistance of each and then you will know for sure. You could also use a brass bushing in your head so you can mount your original sender unit, by the way 200 degrees isn't too hot. It sounds like your T- Stat hasn't opened though with the temp differance between the top hose. Turn your heater on to full hot too to help with purging the air out of the system. Good luck :nod:
 
I just re-read your post. I think you have an air bubble. When you run the engine with some air still in the coolant space, it gets (much) hotter than the target temp. Then, when you turn it off, the water settles in the block and heats up above the target temp. If you start it shortly after, the temp will read way too high. This also happens when the coolant jacket is full. It heats up and then cools off as you run it. Once the coolant passages are full of water, the temp will rise and fall, but not so much.

Of course, a lean burn will cause overheating too. Make sure all the air is out of the block/radiator first.
 
:unsure: A little hint on filling or refilling a cooling system.When draining,have the vehicle nose down.When filling,have the vehicle nose up.That will help to get the air out of the system.
Have used this method for a few decades,and it works well.
Good luck.Have fun.Be safe.
Leo
 
Hi, I do the small hole in the thermostat now, but it is not really necessary on these engines. Since you get hot water to the heater the bypass is "taking care" of any air lock. Once you said the upper hose is cold to the touch, and then you said there is flow through the radiator. If there is flow through the radiator the thermostat is opening. It will open and close cycle a few times until the engine is warmed up, then the upper hose will get hot. As mentioned, keep filling until an inch below the top. I'm sure the T stat spring is in the engine, or it would not open. It sounds normal. I would trust the temp gun, behind and in front of the thermostat. All the gauges on my Bronco read low. Good luck
 
Thanks for the advice guys, I just came back in from running the car without the radiator cap and as soon as the t-stat opened I got some more air out of the system. The temp gauge never went above the half way point and when the t-stat opened it settled in at about one quarter on the gauge even after reinstalling the cap.

I let it run for about 10 minutes while fiddling around trying to get the base idle set. I went ahead and re timed the engine at 14 degrees without the LOM line connected at had it idling at 900 RPM in gear and running smooth. When I reconnected the line the RPMs jumped to 1100 and 42 degrees advanced. I ran out of adjustment on the base idle screw on the Holley 1940 and was only able to drop the RPMs to 1000 with a surge of+/- 50 RPM. I then tried to lean it out to drop the RPM's until my eyes started burning with very little success. I am letting the car cool down again before going back out to do battle again.

So here is the new question, Where should the LOM line be connected for vacuum? I currently have it on the body of the carb, right below where the automatic choke tube goes. The vacuum source for the automatic transmission is on the intake log with a single barb and the PCV valve is a single hose that goes to the carb spacer. Does this all sound correct? I ran the car for 2 years this way without issue and had it idling much smoother than now.

Sorry about the revolving question but I can't find a vacuum diagram in my 1964 Comet and Falcon manual or the 1965 Mustang manual.

Again thanks for the help, all replies and advice are welcomed!

Kevin
 
ags290":1qkgxmxr said:
Thanks for the advice guys, I just came back in from running the car without the radiator cap and as soon as the t-stat opened I got some more air out of the system. The temp gauge never went above the half way point and when the t-stat opened it settled in at about one quarter on the gauge even after reinstalling the cap.

I let it run for about 10 minutes while fiddling around trying to get the base idle set. I went ahead and re timed the engine at 14 degrees without the LOM line connected at had it idling at 900 RPM in gear and running smooth. When I reconnected the line the RPMs jumped to 1100 and 42 degrees advanced. I ran out of adjustment on the base idle screw on the Holley 1940 and was only able to drop the RPMs to 1000 with a surge of+/- 50 RPM. I then tried to lean it out to drop the RPM's until my eyes started burning with very little success. I am letting the car cool down again before going out to do battle.

So here is the new question, Where should the LOM line be connected for vacuum? I currently have it on the body of the carb, right below where the automatic choke tube goes. The vacuum source for the automatic transmission is on the intake log with a single barb ant the PCV valve is a single hose that goes to the carb spacer. Does this all sound correct? I ran the car for 2 years this way without issue and had it idling much smoother than now.

Sorry about the revolving question but I can't find a vacuum diagram in my 1964 Comet and Falcon manual or the 1965 Mustang manual.

Again thanks for the help, all replies and advice are welcomed!

Kevin
Click to expand...

You got some problems there with tune the idle RPM is way too high. Try base lining the tune back to factory specs to see if it helps any. Your vacuum hook ups all sound like they are right, but a picture would help verify that. You may have a bad vaccum leak though that is causing the high idle RPM.

Early 1965 Mustang 170 with an Auto trans the stock tune up specs are these.
Set the plugs to .034 gap if you have the stock type points set them to .025 or 37 to 42 degrees dwell. Base timing is set to 12 degrees BTC. Idle is set to lean best idle RPM then curb idle is set to 525 RPM in drive. Auto choke should be open fully too before setting carb.

Good luck :nod: edited
 
Bubba,

Thanks for the reply. I have the plugs gapped at .035, I reset the timing at 12 degrees and have a Petronix points conversion, with these settings it runs better, but not right. I am wondering if I could have a vacuum leak from either the base of the carb or the base of the spacer. I put fresh gaskets on both . I will put a wrench on the bolts and studs and make sure that they are tight. I will also play with the PCV valve. I replaced it and the grommet so those are new to the equation along with the barb for the transmission vacuum line that I moved between heads. Could there be another vacuum port on the new head that I missed? Is there something else I should check for the vacuum leak? I hate to start spraying carb cleaner on all of the pretty fresh painted parts looking for a vacuum leak.

Kevin
 
Hi, make sure the bolts and fittings are snug, not tight. Recheck the vacuum lines and hoses. Carb cleaner spray should not make a mess. Use the little straw for more control. A vacuum leak will cause your idle problem. Also make sure your choke is fully open and you are off the fast idle cam. Good luck
 
.035 on plug gap is also ok, with a Pertronix and a little hotter coil you can even go to up to a .044 - .045 plug gap for a bit better performance. There isn't all that many places for vacuum leaks on these early Ford six heads. The one port on the intake that your transmission Moduel line is hooked to and carb base gasket plus the lower gasket under the PCV adapter plate, then the hoses going to trans line, the PCV, and the LOD line, that is about it. If you don't have any hose clamps on the PCV line at the adapter plate you might install one there. Another way to check for a vacuum leak without making a mess is to use some smoke. Good luck :nod:
 
Found the leak! My son was dying to drive the car. He hadn't driven it since leaving for College after Christmas break. I figured we couldn't hurt anything so I said lets go, just in the neighborhood. We backed out of the driveway and went to accelerate and there was no 1-2 shift. Ah Ha! Turns out I had knocked the elbow for the transmission modulator off when crawling underneath to loosen the exhaust in preparation to remove the head. I don't fit under these cars like I used too, fat and fifty doesn't give you a lot of ground clearance. Anyway all is well! The idle is set at 500 and you can barely tell it is running. Coming to a stop it just purrs. The cooling gauge went to the half way point then dropped once the t-stat opened and ran at the one quarter mark.

I will continue to watch the coolant level and try to burp it over the next few days along with watching the oil to make sure we don't commingle fluids. My son is so proud of how this turned out. I cannot tell all of you how thankful I am for all of your help and for the forum.

One proud Dad,

Kevin
 
Sounds like U did pretty good! things R as they should B.
Congratulations
 
:beer: congrats on finding the problem and getting it back running as it should. (y) :nod:
 
The heater bypasses the thermostat if you have it plumbed the way they did it in 64. I don't know what temp stat you are running but if it's 190 or 195 try a 180 and get a good one.
 
Seth,

I am running a 190 degree thermostat and I do have the heater lines run the way they were from the factory. I believe it is a Stant or Motorcraft thermostat. What would you recommend as a good one?

Kevin
 
Test your thermostat before you install it. It sounds like don't you have excessive air in the system if your heater valve is open and you are getting heat to the heater while the engine is 190+
 
:unsure: as a side note for those that might read this post after OP. It does make a difference in having a good working heater if the heater hoses are not hooked up correctly. The Supply Hose starts at the top radiator hose / T State housing and goes through the (carb heat plate / PCV adapter plate on early cars) and then on to the lower heater hose fitting. The upper heater hose fitting (Return Hose) goes to the water pump fitting. See below link in the third post down for an illustration of the factory heater hose routing. Good luck :nod:

http://forums.vintage-mustang.com/conco ... 966-a.html
 
You must log in or register to reply here.
Back
Top