So, I'm still overheating, cant figure it out. Timing is correct, and determined today the radiator is doing its job.
Setup:
new 383
edelbrock high flow aluminum water pump.
26" core radiator
dual spals

today I pulled the spal's off, but the shroud back on, and bolted up the mechanical fan. this thing pulls MUCH more air than the spals... like a friggin wind tunnel. Start the car, idle for 15 mins and it heats right up... upwards of 240-250*. got out the IR temp gun and raised the car a bit.. water going into the radiator is 230* and the water coming out is 112*.... so the radiator is doing its job. why is it still running so hot? flow restriction maybe?

thanks.

 

Just for kicks......back your timing way way down. See what happens. I did this, and my temps evened out. Also borrow another timing light, mine was way off......showed 14, but was at 23*.

 

i'll try that out.... my light is a real cheapo.

 

I'm still thinking I have air in the system... when cold, should the upper radiator hose be dry? cause mine is.

how do I properly burp the system when I dont have a cap on the radiator? my fill location is on my expansion tank.

thanks.

 

Take the thermostat out and drill a 1/16" hole in it. Reassemble and fill through the expansion tank with the engine running. Sometimes these thermostats can seal shut pretty good, trapping air in the engine. You then think you have it full when it really isn't.

BigBlockk

Later.....

 

Take the thermostat out run car if it does not overheat either the thermostat is bad or the intake gaskets are backwards

 

no, if yors system is filled with coolant enough the upper hose won't be dry. If you try to remove the upper hose it should come flowing out.

I wouldn't recommend running it without the t-stat in it. you can check the t-stat by removing it and checking it in a pot of water on the stove with a thermometer and watch to see at what temp it opens up.

I ran into the same issue a few weeks back trying to get my system filled up all the way.
I filled the radiator as full as I could and left the cap off so I could monitor the level. started the car and ran it up to temp. when the t-stat opens up you should be able to see the coolant level drop so fill it back up until it at the top again. It took a few times doing this until I could get it filled up. Also, when it's hot and you shut off the motor check the level in the overflow tank and if it's not up to the "HOT" line add more coolant to the tank until it is and run it again.
It's also a good idea that while running the car and monitoring the coolant level that you put the heater on full hot. This will open up the heater box to allow coolant to flow into it. If it's closed you can trap a lot of air in there so open it up.

 

Something is goofy....no way the inlet temp to radiator should be 230* and the inlet back to motor should be 112*.

I don't think there is an automotive radiator in the world that will take 100* out of the coolant as it passes through. More like 10*-40* maybe max.

I think you are on right track on making sure it's full. Try pulling upper hose loose at whichever is higher..the intake or the neck and fill it through the hose until it comes out the opening on either radiator or t-stat housing. Then quickly put hose back on. As long astank is higher than radiator, it should get remaining air out there too.


JIM

 

I've got a hole drilled in the T-stat, and its definatley opening... the upper hose is cool, till the temp rises... right around 180 I can feel the hot water start to flow through.

427Hotrod... could have been a bad reading, had the car 2' off the ground on the lift so I could crawl under and get a reading off the lower hose connection. tight spot there.

so, it sounds like my upper hose should be full of coolant when the car is cold, but I'm pretty sure my expansion tank is lower than this level.... what gives? I'll try and fill it up tomorrow.

thanks again

 

If, and I stress if, the inlet is 230 and outlet is 112, then I would be looking for water flow issue. The only way fluid could cool down that much would be if the water was staying in the radiator much longer than it should, or the air flowing through the radiator is -40 and you are driving 100mph.

To ensure it's not due to trapped air or that the thermostat is not opening all the way, I would remove the thermostat just to see what happens. I would run without the thermostat for daily driving, but there is nothing wrong with removing the thermo for troubleshooting.

Did the problem start after changing somehting, say a water pump, thermo, hoses????

The expansion tank is normally lower than the top of the radiator. As the cooling system heats up, and builds more presure than the cap can handle, overflow will be pushed into the expansion tank. When the engine cools down, and the water contracts, a vacum will be created and draw fluid backinto the radiator.

 

the problem started after I put the new engine in. It ran good for a while, temp around 190* but it kept blowing out coolant... because i overfilled it.... so i thought. but now im thinking there isnt enough coolant, as the upper hose is dry when cold.

tomorrow i'll pull the thermo, fill it up from the upper hose, and let it run again. i'll also try and get a better temp reading off the radiator outlet. its a little unsettling crawling under the car when its running . i gave it one quick shot with the IR then got outta there.

a friends shop has a cooling system vacuum pump... should i bother them to borrow it?

 

Before I go too far, I am by no means a ceritfied mechanic. Just an old DIY'er.

Please excuse some of the following questions, as they may seem dumb, but I will ask anyway. I'm not familiar with cooling systems earlier than my '73, which is the only Vette I have had, so I will assume it is similar, in that the radiator cap is on the radiator and not on the expansion tank.

I find it alarming that it is blowing fluid out when only 190. Is the cap on when it is blowing out the fluid? If it is, and I really hate to mention this, but it sounds like you have a blown head gasket or a really bad crack that is allowing compression to enter into the cooling system. I hope I'm wrong, but. . .

I had a blown head gasket on a '57 I had more years ago than I care to admit, which had similar symptons. It heated up rather quickly and would purge fluid. I took out the thermo, filled the system with water and watched for bubbles. Unfortunately, bubbles are what I saw. I'm not sure if a vacum pump would help or a compression check. I would first do a compression check. If all cylinders are where they should be, then a vacum pump may be helpful.

 

Typically, IMO, fluid blowing out is a thermostat problem....pull it out and run the car hard...that should answer the possible thermostat problem and push any trapped air out....IMO

 

I was thinking about this on the way to work this morning. If the radiator cap is on the expansion tank and teh expansion tank is below the top of the Radiator, then it would be difficult to get all the trapped air out. I am still inclined to remove the thremo and see what happens. Hopefully there is someone watching that is familiar your cooling system that can help.

 

heading over to work on it now... did a little thinking while tryint to sleep last night. this problem was happening last year, but had to go to Florida for work, so didnt drive it much last summer.

last year, it would heat up, so I'd pull the upper hose, and dump more coolant in. ran good, nice and cool. but whenever I'd step on it, it'd blow out a bunch of coolant from the overflow... and keep blowing it out until its at the point I'm at now... coolant level finally leveled out, but overheating.

I'll report back later. Im going now to pull the thermo and fill 'er back up.

 

I was having a hard time burping mine too after the new engine install. I was concerned that it was my Victor Jr. contributing to the problem since the t-stat housing is elevated above the intake valley along with the intake plenum. This put the t-stat housing and upper hose well above the tank on the passenger firewall. I asked in another post if other people had a problem with that. It does not seem to be a problem, so I would not get too hung up on the amount of coolant in the upper hose when cool. I know my upper hose purges when the engine cools down, but since it looks like I've gotten the air all burped out of the block, she runs cool now.

To burp mine, I parked it in the driveway with the nose high. I took the cap off, and ran it for probably 15-20 minutes, constantly adding distilled water and antifreeze. I kept the tank full to the top since the flow was churning the coolant in the tank. It would periodically spit a bit out, but by being patient and constantly adding a little at a time, I was able to get it to take more and more. When it went for three or four minutes and would not accept any more coolant without spitting it back out, I shut it down and installed the cap. I've not had any more problems since. BTW....keep an eye on the temp gauge the whole time and if you have an electric fan, put 12V on the AC sensing line to keep the fan running all the time on high.

 

yeh is does sound like Air in the system....

 

Try the Moroso thermostat adapter - it has a fitting on top to hold a rad cap - and also has a weep tube to go to your expansion tank. I use this on all my Vettes - with a Stant Lever-Vent cap. When the motor is HOT open up the lever-vent (don't turn the cap to open it) and let some gas escape to the overflow tank. This will purge your system with little or no hassle.

 

the easiest way i found to burp the car is to jack the right front up with the engine cold...tak a funnel and put in the rad opening and start the car...when the temps come up, the air will work it's way to the highest point in the system...

 

so here's my update...

it was air... but it was only in there because the system builds up too much pressure when I lay into the throttle, it then spits the coolant out of the overflow. I've tried a new 16lb cap, same thing. Fill 'er back up with coolant, and the temp stays nice and steady. No water in the oil, and no smoke out the tailpipes whatsoever. Only thing I can think is that my high flow water pump is pushing TOO much water, and overpressurizing the system. Today I put the carquest replacement pump back on the car. fired it up, idle for 20 mins and the temp stays good. I just need to take it out for a spin now and rip on it a little to see what happens. hopefully it will refrain from and keep itself cool.