71 454 pressure testing cooling system
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
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71 454 pressure testing cooling system
Having problems with cooling system,, my old radiator 4 core kept the 454 at 180 with 16 in electric fan. I went with a new aluminum radiator because it was having cooling problems,, the new radiator is 3 core CC1215 and should cool better ???, I don't think that's the problem,, the old radiator blew the hose coming from waterpump to the expantion tank,, it is a 71 ls5 car with automatic and ac,, question,, should there be circulation I can see in the expantion tank ? seems like it was circulating before and I could see it well,, if so then I need to see if I have stopped up lines,, the expantion tank gets hot and radiator so I think the waterpump is working right,, but no circulation that I can visually see in the expantion tank,, next, I pressure tested the system with 16 pounds on the tester, cranked the car up and ran for just a minute and it started raising up to higher lbs, over 18 is this normal, now I am going to test with no pressure on tester and see what happens,,, any sugestions , I tried using block tester but I don't have a lot of trust in this,, it tested negative for exhaust gasses.
Last edited by Dane Laney; Jul 9, 2015 at 02:17 PM.
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
when cold I pumped pressure tester to 16lbs and ran engine,, the pressure climbed, now I just tested it with no pressure on the tested when engine a bit warm, and it only went up to 8 lbs pressure and temp climbed to 200 range,, I pumped up the pressure tester with engine warm and running and it didn't seem to keep going up,, when I shut engine down,, pressure drops and I know if I keep pumping it up,, it has to go somewhere,, I should take out plugs and see if water comes out when I turn it over but right now Im tired of burns from the headers,,,,, I was in hope that the first test of climbing pressure when cold, would tell me something,, or no visucal circulation of water in expantion tank, I don't have water in oil,, I don't seem to be loosing any fluid in an amount I notice,, I may try to take a hwy cruse and see if temp drops, then I will know I need more fan,, but don't see why it worked before, with stock radiator at idle and hwy and not now with a better radiator, ?
Last edited by Dane Laney; Jul 9, 2015 at 02:16 PM. Reason: to explain better
Melting Slicks
Joined: Jan 2014
Posts: 2,478
Likes: 254
From: Downers Grove Illinois
when cold I pumped pressure tester to 16lbs and ran engine,, the pressure climbed, now I just tested it with no pressure on the tested when engine a bit warm, and it only went up to 8 lbs pressure and temp climbed to 200 range,, I pumped up the pressure tester with engine warm and running and it didn't seem to keep going up,, when I shut engine down,, pressure drops and I know if I keep pumping it up,, it has to go somewhere,, I should take out plugs and see if water comes out when I turn it over but right now Im tired of burns from the headers,,,,, I was in hope that the first test of climbing pressure when cold, would tell me something,, or no visucal circulation of water in expantion tank, I don't have water in oil,, I don't seem to be loosing any fluid in an amount I notice,, I may try to take a hwy cruse and see if temp drops, then I will know I need more fan,, but don't see why it worked before, with stock radiator at idle and hwy and not now with a better radiator, ?
Burning Brakes
Joined: Apr 2008
Posts: 1,222
Likes: 93
From: shelbyville West Michigan
Ditto. Not sure why you would pressure check and then start the engine? I guess you could put the gauge on and run it to see if it over pressurizes due to bad head gasket, but you wouldn't pressurize it to 16, and then run it, with nowhere to bleed off excess pressure...
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
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If the pressure tester connects where the radiator cap goes then you no longer have the built in pressure regulation of the cap. If your expansion tank is like mine there will be no circulation in it. The level can go up a little when the engine heats up and some coolant expands out through the radiator cap and go back down as it cools off. When you changed the radiator did you make sure to replace all of the seals? Did you change anything else, such as the ignition timing? You do have the shroud back on and the fan working correctly, don't you?
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
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Ditto. Not sure why you would pressure check and then start the engine? I guess you could put the gauge on and run it to see if it over pressurizes due to bad head gasket, but you wouldn't pressurize it to 16, and then run it, with nowhere to bleed off excess pressure...
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
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All seals are good, my expansion is one that comes on the Ls5 with AC , it may be 1971 only with 454, ac and automatic , good to know there is no visual circulation in the expansion tank,, I could of sworn I saw it swirling around with cap off at earlier date,, but if expansion tank and radiator is getting hot then the water pump must be working
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Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
Do these tests with the engine not running. Cold engine, pump up tester to 16-18 psi does pressure hold?
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Last edited by AzMotorhead; Jul 9, 2015 at 07:06 PM.
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
Do these tests with the engine not running. Cold engine, pump up tester to 16-18 psi does pressure hold?
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
Having problems with cooling system,, my old radiator 4 core kept the 454 at 180 with 16 in electric fan. I went with a new aluminum radiator because it was having cooling problems,, the new radiator is 3 core CC1215 and should cool better ???, I don't think that's the problem,, the old radiator blew the hose coming from waterpump to the expantion tank,, it is a 71 ls5 car with automatic and ac,, question,, should there be circulation I can see in the expantion tank ? seems like it was circulating before and I could see it well,, if so then I need to see if I have stopped up lines,, the expantion tank gets hot and radiator so I think the waterpump is working right,, but no circulation that I can visually see in the expantion tank,, next, I pressure tested the system with 16 pounds on the tester, cranked the car up and ran for just a minute and it started raising up to higher lbs, over 18 is this normal, now I am going to test with no pressure on tester and see what happens,,, any sugestions , I tried using block tester but I don't have a lot of trust in this,, it tested negative for exhaust gasses.
Last edited by Dane Laney; Jul 10, 2015 at 12:13 PM. Reason: wording
Melting Slicks
Joined: Jan 2014
Posts: 2,478
Likes: 254
From: Downers Grove Illinois
I can't believe I did this,, I did purchase new seals for the radiator,, they stayed with the old radiator,, the new one was so tight they wouldn't work, I had always planned on sealing the side,, the biggest rule on cooling a BB C3 sealing the radiator,, yes in deed, just an eighth of an inch was enough for hot air to come back around and cause it to run hotter,,, I do think I still have a leaky head gasket, that only leaks at certain temps, But as far as when I sealed the sides and tried it,, it only got to 182 degrees, now it was cooler temp outside not in the 90's like the day before,, But I do think I have it where I can drive it a bit,, I am sure the head gasket will continue to get worse,, that is another story,, thanks all for the help.. I still can't believe I forgot to get back to the seals the sides,, so now I'm going to go for a ride today and see what happens,, thanks again for all the help. I forget more each day but driving a monster around seems to make it all better
Burning Brakes
Joined: Apr 2008
Posts: 1,222
Likes: 93
From: shelbyville West Michigan
if you have a bad head gasket and it only leaks a little, and continues to get worse, you are asking for a destroyed motor. it can eat away at head, block, you know what coolant in the oil does to a bearing for even a short time?
SBC's are a dime a dozen, period big blocks are another story. I'd have those heads off this weekend if it were me...couple bucks in gaskets and anti-freeze, and in a few hours your back in business...
SBC's are a dime a dozen, period big blocks are another story. I'd have those heads off this weekend if it were me...couple bucks in gaskets and anti-freeze, and in a few hours your back in business...
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
Do these tests with the engine not running. Cold engine, pump up tester to 16-18 psi does pressure hold?
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Warm engine repeat 16-18 psi does pressure hold?
Remove spark plugs and pressurize cooling system. Does pressure still hold?
If yes will it hold pressure for more than 1 hr?
If yes to all cooling system is sound. If no you have a leak. Be sure to verify heater core is not leaking before condemning engine.
Test your radiator cap does it hold pressure to its rated psi? does it vent if over pressurized?
One thing to remember water heaters are made to suck. any hose running to the water pump is feeding it. Water is drawn into the pump via the hoses and pushed out the back into the block
Last edited by Dane Laney; Jul 10, 2015 at 02:16 PM. Reason: wording
Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
As it cools some pressure will drop. From 16 to 12 I think would be acceptable. As long as you don't lose all the pressure as it sits.
On these type of older cooling systems it was common to always hear a little "Glug Glug" from the coolant as you undid the cap
On these type of older cooling systems it was common to always hear a little "Glug Glug" from the coolant as you undid the cap
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
if you have a bad head gasket and it only leaks a little, and continues to get worse, you are asking for a destroyed motor. it can eat away at head, block, you know what coolant in the oil does to a bearing for even a short time?
SBC's are a dime a dozen, period big blocks are another story. I'd have those heads off this weekend if it were me...couple bucks in gaskets and anti-freeze, and in a few hours your back in business...
SBC's are a dime a dozen, period big blocks are another story. I'd have those heads off this weekend if it were me...couple bucks in gaskets and anti-freeze, and in a few hours your back in business...
Last edited by Dane Laney; Jul 14, 2015 at 10:36 AM.
Thread Starter
Heel & Toe
Joined: Jan 2012
Posts: 15
Likes: 0
yes sir,, I didn't forget to do that,, I think it was just the seals on the sides,, brain freeze,, I am going to go for a ride today finally to see what happens,, I have it at 180 degrees at mid afternoon warm at idle, and that's where it ran before,, it did drop down to 160 on interstate I am now remembering that,, I never had the front spoilers to put more air into the radiator,, there was never a need but I always wanted too,, so eventually that will happen,, hopefully it will run the same temps it always did and everything will be fine,, thanks for your interest and help
Drifting
Joined: Sep 2014
Posts: 1,430
Likes: 59
From: Long beach NY
St. Jude Donor '15-'16, '18
yes sir,, I didn't forget to do that,, I think it was just the seals on the sides,, brain freeze,, I am going to go for a ride today finally to see what happens,, I have it at 180 degrees at mid afternoon warm at idle, and that's where it ran before,, it did drop down to 160 on interstate I am now remembering that,, I never had the front spoilers to put more air into the radiator,, there was never a need but I always wanted too,, so eventually that will happen,, hopefully it will run the same temps it always did and everything will be fine,, thanks for your interest and help