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Leak Down Test Help


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#1 fdmays

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Posted 29 March 2018 - 03:04 AM

Looking for some advice. Been getting mayonnaise in my valve cover and under my oil filler cap. Thought it was from the car having sat for a while, but it continues to come back even after 2 recent oil changes and a few long drives. Thought it could be a possible head gasket thinking that coolant is getting in and mixing with the oil, so I did a compression test and had 180 psi across all 4 cylinders. Check. Figured the next step would be to do a leak down test. Here's where it gets interesting, all 4 cylinders are showing around 45 - 50% leakage and I can hear the air coming from the vent in my oil filler cap on the valve cover. Any thoughts here? I'm thinking I'm going to pull the head this weekend and take a look at the valves, gasket, and head., but figured I'd ask first.

#2 Spider

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Posted 29 March 2018 - 04:22 AM

Personally, as the Compression Test seemed healthy, I wouldn't get too hung up on a Leak Down Test as it's a static test and the motor is in a dynamic state when running.

 

Also, while the compression test may have been OK, it doesn't necessary mean there's not a leakage path via the gasket from the cooling passage to the push rod holes (and that leads to the sump).

 

Are you loosing coolant?

 

Is there any oil in the water?  (not that this is conclusive)



#3 minidaves

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Posted 29 March 2018 - 06:24 AM

leakdown is just that leakage, your rings are wornout



#4 minimans

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Posted 29 March 2018 - 07:11 AM

Are you sure your doing the test correctly? TDC firing position with piston static at the top? If all the cylinders read the same low figure I'd be a suspect of the method or gauge personally



#5 Dusky

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Posted 29 March 2018 - 07:59 AM

Does your coolant level go down?
Have you got the breathers fitted and connected to the carb? I could pour out water when I had those pesky k&n breathers 'filters'

#6 ACDodd

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Posted 29 March 2018 - 12:00 PM

With figures that bad check out the valves.

Ac

#7 Northernpower

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Posted 29 March 2018 - 12:18 PM

I'd whip the head off. You don't say what type of engine it is but working on the assumption it's a carb type then it won't take very long at all. If it's injection obviously it'll take a little longer but still worth it. Besides it'll be a nice Easter project.



#8 fdmays

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Posted 29 March 2018 - 12:22 PM

Yea, test was done at TDC for each cylinder. Wondering if it's my guage, but still getting mayonnaise regardless. I'm losing some coolant for sure. I've got the crankcase breather filter installed. Also, theirs a blanking plate at the mechanical fuel pump location. I'm running a 45 Dcoe and there isn't any other lines connected to it minus the fuel line. My intake manifold does have a servo nipple that's currently capped and not being used. Wondering if I should remove the blanking plate and run a breather line to the intake manifold. Ideas?

#9 fdmays

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Posted 29 March 2018 - 12:54 PM

Yup sorry she's a 1380 with a stage 3 head and 45 dcoe weber. The interfering thing is that the leakage is consistent across all 4 cylinders.

#10 Spider

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Posted 29 March 2018 - 06:37 PM

 I'm losing some coolant for sure.

 

I'd suggest taking the head off and going from there.

 

It could the something as simple as the gasket (most likely) or it could have a crack in the head.



#11 fdmays

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Posted 30 March 2018 - 02:05 AM

Alrighty, heads coming off this weekend. So next question, since I'm taking the head off, head gasket is getting replaced. Thoughts on Bk450 VS cometic?

Edited by fdmays, 30 March 2018 - 02:06 AM.


#12 Sprocket

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Posted 30 March 2018 - 07:59 AM

Some Mayo is normal in this cold weather especially when it is an atmospheric crankcase vent.

Edited by Sprocket, 30 March 2018 - 07:59 AM.


#13 Retroman

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Posted 30 March 2018 - 03:35 PM

To my way of thinking its the head gasket...

 

You have water in the oil and its using water.

 

Sometimes you never find out what the cause is.....generally specifically or in life

 

A BK450 will be fine for you assuming its a recently bought one.






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