Question about pressure testing cooling system
03-23-2013, 05:56 PM
#1
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Question about pressure testing cooling system
1999 Jeep Cherokee Sport, 6cyl, 4l
I just installed a new radiator. Did not replace the hoses, as they seem to be in good shape. I pressure tested with a Mityvac MV4560 pressure tester, and the system does not hold pressure with the engine cold. I put it under pressure up to 15, and the number on the radiator cap is 16. As per the tester instructions, I also let the engine heat up to running temp with the tester attached, then shut off the engine and let the motor cool. I watched for leaks from hoses but did not see any. The tester did not show any indication of a head gasket problem or cracked block. I have not seen any coolant leaks under the car where it was parked after driving it. So, can't see leaks but the system won't hold pressure. Where do I go from here? Does it seem like there is a problem or is this tester just not reliable? I did bleed the air out of the system but I think there may still be some in there. Would that affect the pressure test? Thanks.
I just installed a new radiator. Did not replace the hoses, as they seem to be in good shape. I pressure tested with a Mityvac MV4560 pressure tester, and the system does not hold pressure with the engine cold. I put it under pressure up to 15, and the number on the radiator cap is 16. As per the tester instructions, I also let the engine heat up to running temp with the tester attached, then shut off the engine and let the motor cool. I watched for leaks from hoses but did not see any. The tester did not show any indication of a head gasket problem or cracked block. I have not seen any coolant leaks under the car where it was parked after driving it. So, can't see leaks but the system won't hold pressure. Where do I go from here? Does it seem like there is a problem or is this tester just not reliable? I did bleed the air out of the system but I think there may still be some in there. Would that affect the pressure test? Thanks.
Last edited by Cameron58; 03-23-2013 at 06:01 PM.
03-23-2013, 06:34 PM
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Year: 1999
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How fast does the pressure drop? Details please.
If an inspection of the radiator, hose connections, heater core, water pump, water outlet, freeze plugs and engine reveals no obvious external leaks, the coolant may be escaping internally through a leaky head gasket or cracked block or cylinder head.
Are you having to add coolant to the reservoir?
If you are not having to add coolant and have no other symptoms, it is more likely that you have an external leak somewhere. And you just need to find it!
Start with snugging up your hose connections and retesting. If still seeing a drop in pressure, get under the front of the vehicle with a good light and perform a comprehensive inspection with the best light you can get your mitts on.
Good luck and keep us updated!
If an inspection of the radiator, hose connections, heater core, water pump, water outlet, freeze plugs and engine reveals no obvious external leaks, the coolant may be escaping internally through a leaky head gasket or cracked block or cylinder head.
Are you having to add coolant to the reservoir?
If you are not having to add coolant and have no other symptoms, it is more likely that you have an external leak somewhere. And you just need to find it!
Start with snugging up your hose connections and retesting. If still seeing a drop in pressure, get under the front of the vehicle with a good light and perform a comprehensive inspection with the best light you can get your mitts on.
Good luck and keep us updated!
Last edited by tjwalker; 03-23-2013 at 06:40 PM.
03-23-2013, 10:50 PM
#6
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The pressure tester has a cap that goes on in place of the radiator cap. A hose goes out of it to a hand pump with a gauge. The pump is used to pressurize the system. I suppose the cap that is part of the tester could be not quite tight enough, but I don't know of any way to test for that. Maybe I'll try pressurizing with the pressure tester while pushing down on the cap as hard as I can. If the cap is not tight enough maybe that will seal it.
Last edited by Cameron58; 03-23-2013 at 10:56 PM.
03-23-2013, 10:54 PM
#7
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The needle on the pressure tester gauge drops from 16 down to 0 in about five minutes. I don't have to add any coolant. I just changed the rad yesterday and have only drive the car a few times since. But, I checked last night after driving and today after driving, and I did not have to add any coolant at all.
How fast does the pressure drop? Details please.
If an inspection of the radiator, hose connections, heater core, water pump, water outlet, freeze plugs and engine reveals no obvious external leaks, the coolant may be escaping internally through a leaky head gasket or cracked block or cylinder head.
Are you having to add coolant to the reservoir?
If you are not having to add coolant and have no other symptoms, it is more likely that you have an external leak somewhere. And you just need to find it!
Start with snugging up your hose connections and retesting. If still seeing a drop in pressure, get under the front of the vehicle with a good light and perform a comprehensive inspection with the best light you can get your mitts on.
Good luck and keep us updated!
If an inspection of the radiator, hose connections, heater core, water pump, water outlet, freeze plugs and engine reveals no obvious external leaks, the coolant may be escaping internally through a leaky head gasket or cracked block or cylinder head.
Are you having to add coolant to the reservoir?
If you are not having to add coolant and have no other symptoms, it is more likely that you have an external leak somewhere. And you just need to find it!
Start with snugging up your hose connections and retesting. If still seeing a drop in pressure, get under the front of the vehicle with a good light and perform a comprehensive inspection with the best light you can get your mitts on.
Good luck and keep us updated!
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03-23-2013, 11:01 PM
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mix up a bottle of dish soap and water, thick enough to be clingy and squirt around the cap area and watch for bubbles.
If this is a rent-a-tester, lord knows what's been done with it. May well be not sealing on the radiator.
If it isn't there you can soap up the hose connections too and look for Mr. Bubble. Heater hoses too.
If nothing there, listen carefully at the throttle body and exhaust for escaping air (not good to find)
If this is a rent-a-tester, lord knows what's been done with it. May well be not sealing on the radiator.
If it isn't there you can soap up the hose connections too and look for Mr. Bubble. Heater hoses too.
If nothing there, listen carefully at the throttle body and exhaust for escaping air (not good to find)
03-24-2013, 03:42 AM
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Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
The pressure tester has a cap that goes on in place of the radiator cap. A hose goes out of it to a hand pump with a gauge. The pump is used to pressurize the system. I suppose the cap that is part of the tester could be not quite tight enough, but I don't know of any way to test for that. Maybe I'll try pressurizing with the pressure tester while pushing down on the cap as hard as I can. If the cap is not tight enough maybe that will seal it.
03-24-2013, 03:30 PM
#10
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Thread Starter
OK, I tested the radiator cap, and it holds pressure just fine. No problems there. But, when I pressure test the cooling system the radiator cap is not in place. The cap that is part of the pressure tester is on the radiator.
This is the pressure tester I used. The yellow cap goes on the radiator in place of the radiator cap.
I suppose I'll replace the hose clamps next. I believe the ones on the car are original. They are the type with the two tab that stick up, and you squeeze them together with channel lock pliars to loosen the clamp.
This is the pressure tester I used. The yellow cap goes on the radiator in place of the radiator cap.
I suppose I'll replace the hose clamps next. I believe the ones on the car are original. They are the type with the two tab that stick up, and you squeeze them together with channel lock pliars to loosen the clamp.
What.... pressure test the radiator cap adapter should be in the kit.....Pressure testing Radiator cap. By: Zahid J. - YouTube
04-10-2013, 10:41 AM
#11
Senior Member
Did you ever found out how the pressure was escaping? I am about to do this same procedure this weekend.
I have replaced my entire cooling system on my 98 and thought I had finally eliminated all visible leaks, but this week my reservoir dropped about 1 1/2 inches and I can't find where the leak is. I'm going to be pressure testing and crawling all under the vehicle in hopes of finding an external source of the leak.
I have replaced my entire cooling system on my 98 and thought I had finally eliminated all visible leaks, but this week my reservoir dropped about 1 1/2 inches and I can't find where the leak is. I'm going to be pressure testing and crawling all under the vehicle in hopes of finding an external source of the leak.
Last edited by playbass; 04-10-2013 at 11:00 AM.
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