I have a general cooling system pressure testing question:

As I'm in the process of putting my 250 back together I borrowed a cooling system tester to test my cooling system for leaks before I reassembled everything. I pressured up my EMPTY cooling system and sprayed soapy water to check for air leaking. It worked and I was able to isolate a serious leak around my heater valve, which I was able to fix by pulling it apart and replacing the o-rings. Pressured it up again and no noticeable, or audible leaks.

My question: Should the gauge hold the pressure in the system this way for a significant period of time without leaking down? I know the tester is designed to be used with a full coolinig system and I know that that would change the pressure in the system onced you pressured it up with air. I notice a pretty slow leak on the gauge - about half the original air pressure lost after 3 hours.

Any thoughts?

Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

What pressure are you checking at?

A cooling system is meant to seal for liquids, not gasses. The fact that it holds pressure at all with air alone is a true testament to your assembly of the system. I think you should be fine. Coolant molecules are much larger and have WAY more surface tension than air, so I think you can breathe easy.

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1983 300SD
Rusty, Loud and Proud

I'm not positive - the gauge I borrowed is worn and I can't read the numbers. I know that it's not more than 11-12 lbs though, becuase I can read the upper ranges.

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

I'm with Dieseldoofus on this one. Air will leak out where liquid will stay. Fill it with water and then pressure it to be sure.
Jeff

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1971 R600 Mack toterhome (SuperDawg)
99 NU-WA Snowbird 34+2 SE 102 5er
If it's not diesel, it's not in my stable!
53 F100 617.951/auto
95 Dodge 3500 Cummins/5 speed service truck

I agree.

A cooling system is not designed to be perfectly sealed for gases at 15 psi. If the leakdown occurred over three hours, you can be assured that the liquid will not leak. In fact, it's possible that the gauge itself could be the culprit for such a leak.

I had a hydraulic leak in a custom hydraulic system that we built. It had a hand held Enerpac pump. The 1500 psi system would lose about 50 psi every five minutes or so. Couldn't find any leak even after the system went to zero.

Turns out that Enerpac products are so poorly designed that the pump cannot hold the pressure that it develops. Unbelievable.

A classic example of a company that has the big name in the business and provides total crap as a product.

Thanks guys - that provides some peace of mind as I re-install the manifold assembly.

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

i work in hvac and i can tell you that your minimal loss of air is aceptable for everything including water and hvac systems you are perfectly fine heck have the systems we desighn dont hold so well, you are allowed a 15% leack byt code for buildings i dont know if its the same for cars but its realy has no effect on leackadge or water, you will be 100% fine

Agree that Enerpac is crap.