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Installed a sct x4 tuner and bought a 30 ft RV at the same time and after install I noticed degass bottle started to show coolant leaking under a load what is my next move now? It's my first diesel so advice needed please!!!
 

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"resident smarty pants"
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Put a pressure gauge on the degas bottle.

Where is it leaking at? At the cap?
 

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Installed a sct x4 tuner and bought a 30 ft RV at the same time and after install I noticed degass bottle started to show coolant leaking under a load what is my next move now? It's my first diesel so advice needed please!!!
 

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Yes from the cap. So what put a gauge on it and drive around? What is a number that if I see it's pretty much game over psi wise..? Thanks for responding..
 

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"resident smarty pants"
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If the cap holds the proper pressure, you should see 16 psig if you have an issue. The cap acts as a relief valve and is designed to vent around 16 psig. Sometimes they get weak and will leak at much lower pressures. Normal pressure when everything gets warmed up is around 8-10 psig.

Once everything is warmed up and the degas bottle pressure gets to the max level, then vent the degas bottle (slowly open the cap - I throw a heavy towel over it for safety). Then drive around for say 30 more minutes with some fairly hard accelerations. This will show you if you are getting pressure from something other than the coolant expansion (ie head gasket leak or EGR cooler leak).

Be sure to get a decent pressure gauge. I have not found the Harbor Freight ones to be very good. Tee the gauge into one of the small vent hoses that tie into the degas bottle. IMO it is best to stick a long hose on it so you can bring it into the cab to watch the pressure as you drive. Just make sure you don;t have any connection leaks.
 

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I'm not a mechanic..

However, would it be easier to just throw a new cap on there and see what it does? Caps are cheap.

Are you 100% sure it's coming from the top? Tank cracks are common.

Sent from my Pixel 3 XL using Tapatalk
 

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"resident smarty pants"
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I agree that caps leak. Also, the sealing surface of the cap sometimes gets warped or gets a burr that can cause leakage. Checking the sealing surface is free and you should definitely do that.

Individual preference on trying a new cap or not. IMO I would want to know what the degas pressure is doing - regardless of whether or not I see evidence of a leak. I think a gauge to check coolant pressure is a necessity of owning a 6.0L (and you can use it for a fuel pressure test gauge also - fuel pressure is another thing all 6.0L owners should be watching).

The gauge will tell you if you have a bad cap and it might save you some money if the cap isn't needed.

Just my way of looking at things .....

If you want a new cap, the part number is: 9C3Z-8101-B
 

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"resident smarty pants"
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This gauge is really nice:


and some nice ones here:


 

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"resident smarty pants"
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As an fyi - a pressure gauge with brass wetted parts (the cheap ones) are not recommended for service over 140 degrees. The ones with stainless steel wetted parts are rated for 212 degrees F. The links I posted just above this one are for ones that has S.S. wetted parts.
 

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I got a cheap pool pressure guage from lowes. Might not be the best but it was 10 bucks & helped me identify my head gasket leak. I actually hooked it back up yesterday to make sure I wasn't building pressure anymore. Didn't get over 8. I was making about 18 before & could see the cap bleed off pressure.
 

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"resident smarty pants"
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A REAL cheap and easy thing to do is to use a Schrader valve on the end of a hose. Then you can check the pressure with any old tire pressure gauge.

 

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I replace the cap with a Ford one first, easy and probably needed sooner or later anyway. Then do the get it hot, vent the cap like above, and then drive again, and check and see if it vents out again. If so then rig up a gauge.
 
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"resident smarty pants"
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Many people have small leaks in the coolant system. With those small leaks, they could have a minor head gasket issue, but never spray out of the cap because the excess pressure leaks at a hose or a fitting ..... and that keeps the degas bottle pressure from exceeding the cap pressure limit.

The best way to test for head gasket leaks is to first make sure you have an "air tight" coolant system up to 16 psig. To do that you need a pressure gauge.

Once you know your system doesn't leak, then you can check the pressure rise when driving (and after venting the tank).

If you are interested in doing a proper test, you need a pressure gauge .........
 
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