68 GTX Running Hot?!?

[69L48Z27]

I've been chasing my tail a little bit with this one. Back story - 440 rebuilt over the winter with new 180 thermostat. Car was put back together and fired up, not a lot of miles but enough to shake it down. Temp gauge on the dash was perfectly vertical in the gauge. Looked normal.

Fast forward a bit... I had a small weeping issue around the water neck and hoses with original style clamps, heater hoses. I resealed the water neck at least 3 times and even swapped heater hoses. No luck so I did something I would never do, after reading some posts here it seemed like a lot you do this. I added a bottle of Bars Leak.

At the same time I also had the dash apart to clean it and address a few issues. The temp gauge was intermittent and the reason was the two nuts on the back were not even finger tight. Put it all back together and ran the Bars Leak in as the instructions state.

Also, radiator was out for cooking and pressure testing over the winter too. All good.

Now the gauge runs to the right of where it did before, right in the middle of the inside brackets.

Now I'm think I clogged the radiator with Bars Leaks. I guess my question is - Where on the gauge is normal?

Reference picture of the gauge:

 

[eldubb440]

"right in the middle" of the normal band is "normal"....... if it creeps to the hot side, you have issues

I would hook up a good mechanical gauge for an accurate number, you may be worrying over nothing...... and no more snake oil

 

[dart4forte]

Did you burp the system

 

[BeeKool]

Do you have a temp gun? This is good to double check the accuracy of your temp gauge.
Also, from my experience. Radiator stop leaks plug the heater core first. Maybe that's just my experience.

The original weeping you were having. It's was from between the hose and water neck? Or water neck and water pump housing?
What radiator cap are you using? Perhaps it allows too much pressure to build and forces leaks.

 

[RJRENTON]

The purpose of the pressurized system is to raise the boiling point of the coolant. With a 50% antifreeze concentration (either ethylene glycol dexcool or regular glycol), for every pound pressure the boiling point of the coolant is increased three degrees F. A 15# pressure cap will raise the boiling point of the coolant to 265 degrees F. Propylene glycol based systems operate differently bedside it has a different specific heat characteristics and cannot be compared directly.
I'm not sure why the concern if the coolant temperature gets to 190-200 degrees F. It does not mean that much. If you want to see what the actual temperature is measure the Metal temperature (cylinder head or cylinder sleeves) which will be much higher. Remember that circulated coolant VELOCITY is the key to good heat transfer characteristics...anyone that doesn't think so is wrong. I'm sure there are proponents that Will argue differently. Perhaps one of the these experts will share their calculations to prove their point rather than speculation.
Bob Renton

 

[oldbee]

Sounds pretty normal to me for a fresh rebuilt engine that's still breaking in.

 

[69L48Z27]

Thx for all the replies. I'm assuming based on the stock gauge its hot, but I really don't know if it is. Bad title I guess...

It's burped for sure. Weeping was between the water neck and housing and at both heater hoses engine side. Radiator cap is a new repop 16lb. Builds pressure for sure. I do need to add analog gauges so I can see the temp.

Thx for confirming the needle range for normal. If right in the middle of the center brackets (just past straight up) is normal then I'm right on. I'm okay with the car running over 200* if it wants. I just thought it was odd that it was 'normal' (needle straight up) and then I had the gauge out AND did Bars Leak then all of the sudden the gauge reads to the hot side. Also, it never boiled over or anything either.

I think I'll drain everything and flush it. Then get an analog gauge installed or get a temp gun. Should have one of those anyway.

Thx again!

 

[5.7 hemi]

Get the water neck with the " o ring", problem solved.

 

[PeteBell68]

Flush out the bars leak if you've had the rad tested as stated . For the thermostat housing a gasket and a ring of black permatex .
Mine was weeping I did a ring around the stat and a continuous thin ring around the bolts and and gasket did the bolts up I let it set for 4 days while I worked on other things .
No leaks and runs perfect .
New hoses leak as things get warmed and seat .

 

[69L48Z27]

I have an update... this week I picked up a couple things, temp gun and gauges.

I have more data but I think I still have an issue. I did not flush anything yet.

Ambient air temp was around 70* today. I went for a good drive, 10+ miles and beat up on it a hand full of times. Then I let it idle for probably 15 minutes.

Upper hose with the temp gun right at the thermostat housing was 200* and the lower hose at the radiator was 150*. Pictures of both gauges below. I'm wondering if the thermostat is not opening. It's not crazy hot but it was only 70* out today and I would think it would run closer to 190* all the time. Based on where the gauge, dash, was happy before that's where it was.

Still something going on...

 

[oldbee]

You could be right on t-stat bad, but it oughta be puking out rad.cap. Lower hose has spring in it?(collapsing?)

 

[Dennis H]

A Mancini Billet housing solved the leak for me.

 

[69L48Z27]

Thx guys. It's not hot enough to boil over yet. The lower hose was not collapsed and the system has pressure once it hot.

The circulation look like an issue looking in the radiator once it was hot when I was making sure the air was out. Usually it will look like the coolant is moving around once the thermostat opens but this looks stagnant like there's no flow.

I'm going to flush it and take the thermostat out this weekend and run straight water in it and see what it does once I confirm the thermostat works.

 

[69 GTX]

Make sure your timing and fuel ratio is set correctly, these can lead to a engine running hot.

 

[STREETREBEL]

Thx guys. It's not hot enough to boil over yet. The lower hose was not collapsed and the system has pressure once it hot.

The circulation look like an issue looking in the radiator once it was hot when I was making sure the air was out. Usually it will look like the coolant is moving around once the thermostat opens but this looks stagnant like there's no flow.

I'm going to flush it and take the thermostat out this weekend and run straight water in it and see what it does once I confirm the thermostat works.

If you have no flow I would pull the thermostat or replace it.

 

[69L48Z27]

I still haven't had time to tackle this one. Drove the car this weekend and it stayed at or under 200* the entire time. Shot the hoses with a gun when I got back from my drive and I had 195* on the top hose and 130* on the lower hose. Outside temp was just under 70*.

AF and timing are good.

My 'to-do' list still includes fully draining the systems, flush it with water, and make sure the T-Stat is opening properly. Need to do this before it get hot out, those 90*+ days are coming...

 

[69L48Z27]

Quick update and question, I had time this evening to pull the T-Stat.

The thermostat is interesting in its operation and might be part of the problem. I always imagined the thermostat was like a switch, open or closed, and not a lot in between. I threw the thermostat in a pan of water and observed that the thermostat was only open a very little bit at 180-190*. It did not fully open until almost 205*. It did close pretty fast at 180*. I ran the heat up and down slowly to see what it would do. I was surprised how hot it needed to be in order to fully open. My question is - is that normal? Or should it go 100% open in that 180-190* range. To recap, this is marked 180*.

I may have solved the leaking water neck issue too. I found that the bolt threads (holes) are not that deep and the bolts (original) are only .090" shorter than the holes when installed dry with housing. This was after chasing both the bolts and threads and cleaning the holes out. I think my problem was the bolts were just barely clamping the housing even thought they felt tight. Too much dirt down in the threads.

Also the coolant looks like old nasty antifreeze after the BarsLeak. Last time I'll be using that.

I'll update again after I flush and put it all back together. Thinking I may go with a 160* stat if I hear that thermostat behavior is normal.

 

[Dennis H]

Green coolant. Stant Superstat 180.

 

[Ranger16]

Quick update and question, I had time this evening to pull the T-Stat.

The thermostat is interesting in its operation and might be part of the problem. I always imagined the thermostat was like a switch, open or closed, and not a lot in between. I threw the thermostat in a pan of water and observed that the thermostat was only open a very little bit at 180-190*. It did not fully open until almost 205*. It did close pretty fast at 180*. I ran the heat up and down slowly to see what it would do. I was surprised how hot it needed to be in order to fully open. My question is - is that normal? Or should it go 100% open in that 180-190* range. To recap, this is marked 180*.

The thermostat is rarely ever full open.
This is from Stant. http://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/
"Thermostat Temperatures

• Thermostats have a “rated” temperature such as 180F or 195F
• This is the temperature the thermostat will start to open, give or take 3 degrees
• The thermostat fully open about 15-20 degrees above its rated temperature"
  

 

[ckessel]

Don't forget that stop leak plugs up more than just the leak. Bar's also contains water pump lubricant which is a water soluble oil. Most people get worried if an engine runs more than 180. Some engines just seem to be upwards of 205-210 without any issues and don't forget that a lot of newer stuff is there too so it can meet emission equipment parameters. Colder than 170 is not good either. If you start getting north of 210 you better start checking things out. You are wise to shoot the hot areas with the heat gun, like you are doing already, to verify the readings. Old gauges are not the most accurate. When I had my 70 Challenger, 180 true was just touching the second mark on the gauge which is almost full left. When it got hotter, the oil pressure would head the other way on the gauge. Was not having engine issues, it was just old gauges that needed to be trued up.