Ok, I'm not sure what all the different temps are supposed to be but I'm having an issue with the new motor (383) and need some guidance. I'm running a 160 degree thermostat and My temp gauge inside the car stays between 160 and 180 even when sitting still with the A/C on. But when I shut off the car I can smell coolant and it's boiling inside the overspill tank.

I popped the hood and started shooting different areas with the laser thermometer and at different parts on the headers the temp ranges from 200 to as high as 323 degrees. I could also see that the fuel was boiling (I have a clear container in the line where the filter is, it's an electric fuel pump).

The cap on the radiator is 16 lbs. Do I need a bigger radiator or is it something else? Is my temp sensor screwed up? Obviously coolant doesn't boil at 180, so I don't know if it's just getting hot in the overspill because my 300+ degree headers are right below the overspill tank or what the deal is, or if my temp sensor is waaaay off and I was running hot all this time. Everything seemed to run fine, no issues like you would expect with an overheated motor. This is a fairly new radiator and had no problems with it with my original motor (350 L-82), but maybe it's not up to the task of the 383? This really isn't my area... I don't know what temp I should expect the headers to be, that just seems like it's hotter than it should be.

 

Shoot the thermostat housing and the radiator where the upper hose goes in and see how that compares to the dash gage reading.The headers and the dash gage are like apples and oranges.

 

It was within 4 degrees of gauge reading when I shut it off.

That's what's weird to me ... water doesn't boil until 212, so if the temp is truly only 165 (external reading at tstat housing) then why is it coming out of the radiator into the overspill and boiling out of there? Should I maybe try a cap that's more than 16 lbs since it's obviously more than that or do I need a bigger radiator?

 

Maybe a bad cap? Have you run it long enough to work all the air out of the system?

 

Never had any problems with the cap on the old motor (cooling system is the same) but I guess it wouldn't hurt to try a different one. How long should it take to work the air out, I've run it maybe 3 hours so far and it's boiled in the overspill tank every time. I added about a gallon this morning because I couldn't see coolant in the radiator (was full yesterday).

I'll go buy a cap now, should I buy another 16 lb cap or get a higher one since its a high performance engine?

 

3 hours is plenty it should be out in 10 min.The header temps seem good.If you couldnt see coolant in the rad it must have been low.Is your tank the plastic late model kind that connects to the overflow on the raditor or is it the metal expansion tank.Is your system a closed system like late model or is it the old style that needs some room left inside the rad for expansion and the tank is just a puke catcher and doesnt recycle back in the rad?

 

Could be posible that the water in the system is boiling where the temps are 323 deg and therefore forcing the pressure up enough in the system to blow out the cap in to the tank. what areas of the engine are hottest, is it just around the headers or elsewhere? Could it also be caused by wrong timing or running a bit lean on some of the cylinders?
Just a thought.
Good luck.
Peter

 

Ron, I in Florida too, hotter a 2 buck pistol now....

so, when you are running down the FREEWAY road.....what does your temp run at... what is your state rating, and the BRAND of stat.....

second off, when you pull off the freeway into traffic what does the gauge say at worst temp??

does oil say anything about looking like a chocolate milkshake???

when engine is hot, pop the hood and see if the lower hose collapses under suction from the pump....when you rev engine to say 3500 rpms.....

IF you running reasonable at speed and only hot in traffic, it's obviously the cooling fan setup from the mechanical? fan to the shroud or lack there of....OR you plainly need an electric fan setup like from DeWitt or whatEVER but proper shroud and fan/temp controlls to pull that engine temp down again....

I have found the worst heating problems are in summer, running the freeways, off the ramp into traffic when road temps gotta be some 140f or better...all that traffic on black tarmac and no wind or natural cooling...all them cat converters and engines adding to the mess....

also, where is your temp gauge running from...the head or the water crossover under the tstat housing???

PM email me if I miss this thread....

 

nothing to do with regards to your posted issue but i'd replace the 160º t-stat for a 180º unit.

 

Ron take your rad. cap off and look at the little disc on the inside.Hold the cap up with the disc down-if it flops down replace the cap.Sounds like your not getting your 16 lbs of pressure on the system and the parts of the engine that are getting to 212 are boiling internally and pushing the coolant out-"hot spots"

 

16 is good

 

Sorry for so many questions-You must be working on your 80 since your other 2 are all original.You have the closed system -just about has to be a bad cap-the little disc is staying open and not letting pressure to build.

 

If you have a cooling system tester(pump) put it on in place of the rad cap and see how much pressure you are building after the engine reaches normal temp. If your temp gauge or engine do not register hot, you may be getting combustion into the cooling system and what you think is boiling coolant in the reservior is actually air bubbles from the over pressured radiator. Hopefully that is not the case, but if it is, there is a test kit to check for combustion gasses in the cooling system. Have you checked the temp of the coolant in the reservior? The antifreeze and water mixture will have a boiling point higher than 212* F. Barry K is right about the thermosta, It will be better to change up to a 180*, as your cooling systems ability to dissipate heat will determine the max temp. I would not go higher than the 16 lb cap, that would be too much pressure, I would expect a leak.

 

Latent heat in the engine block & headers will transfer back into the water when you shut off the engine. All will stabilize at the same temp and it will be higher than running water temperature. The added heat can cause the water to boil a little; nothing unusual there. If you don't have a coolant recovery tank to catch the expanding fluid, you should probably add one. If fuel is boiling in the fuel line, you need to put some heat shielding/insulation in place to reduce the heat getting to the fuel line. You might also do away with the site glass gizmo. If that catches a rock or cracks from age/whatever?, you could burn up an engine...or a car...pretty easily.

 

If you don't have a tester, hopefully you can borrow one. I would definitely check and make sure you don't have internal problems.