97 K1500 5.0 Coolant in Cylinder 1

[GoToGuy]

Just a note and update. Originally AC 43.13 stated on Engines less than 1000 cubic inches to use a diff's comp tester with an orifice of .040 / and Engines 1000 cubic inches and larger the orifice shall be .060
This was revised and changed in a 09/2001. It changed the specifics to cylinders less than 5 inch bore use .040 orifice and a 5 inch bore and larger to use a .060 orifice. Regardless of total cubic inches.

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A reminder letter was sent out by the FAA. Copy added.

 

[Schurkey]

I didn't know that it wasn't always that way--the .040 orifice for pretty-much all automotive applications (bore diameter less than 5 inches). It certainly makes more sense to base it off of bore diameter than total engine displacement, since you could have 1000 cubic inches from lots of small-bore cylinders, or just a few big ones; and you're testing one cylinder at a time, not the total engine displacement.

The leakdown tester I linked-to has that .040 orifice. I don't know what size the "Master Orifice" is, that's set by Continental/Teledyne. As I said, the "Master Orifice" is a little big for our purposes, but it's usable as a guide. Otherwise you need to test "known-good" engines of the same bore size as the one you have suspicions about, to get a "feel" for the leakdown tester.

 

[GoToGuy]

In regular periodic checks. Engines you see a lot of you have records of previous test. And any time we had something unusual, abnormal readings, if no other outward indications. Recheck the tool, and go out and do good strong runup, then an immediate recheck that would confirm whatever problem we did or did not have. There have been a few head scratching , well it acts normal now. Full power. Wants to drag the wheels and everything is in the green.

 

[Schurkey]

An advantage you "airplane guys" have is that the FAA regulates the orifice size and shape of leakdown testers. There's no "industry standard" or SAE standard for leakdown testers in the automotive world. Tool makers can do whatever they feel like, and there can be huge variations among manufacturers that would make one tool read "high leakage" and another "low leakage" on the same cylinder under the same conditions.

The orifice in the tester (NOT the "Master Orifice") has as much effect on the indicated leakage as the actual cylinder leakage. I can make a cylinder show any leakage a customer might desire, by screwing with the orifice size. Which is why the Master Orifice is so useful. It sets a lower limit on the allowable pressure indicated, to keep folks honest. Otherwise, as I said--you have to use the automotive tester on known-good cylinders of the same bore size to get an idea of what your questionable engine should show for leakage.

Despite what the magazines and piston-ring advertisements say, it's NOT as easy as deciding that 2% or 10% or "whatever" percent is "acceptable" and readings above that magic number are "bad".

 

[Trig]

Good info.

Ordered 2EM w/14mm adapter. I'll report back once I receive it and get some data.

FYI - for those less knowledgeable I looked at HF's Maddox brand (which looks very similar to the OTC brand) which was thirty less than the one from ATS. However, no master orifice/calibration ability and the build quality is apparent from the pictures alone. Also no parts store locally had anything to rent but ymmv.

 

[Trig]

I was able to get some pressure into each cylinder for a rough and dirty test and found definite leakage on the intake valves on #4 and #6. Aside from that I can hear air moving regardless but with the intake off and my method of shoving an air guns rubber tip into the hole that's all I can for sure say was happening.

The following is a check for operator error on my part as well for the next guy that possibly comes along:

I found TDC for each cylinder by first finding #1 TDC by aligning the engraved line on the crank pulley up with the notch on the timing chain cover. Made sure each rocker arm would wiggle around a bit (otherwise you're at BDC). Then if you rotate 90 degrees you're at TDC for the next cylinder in the firing order, in this case #8. I determined 90 degrees by advancing to the middle spot of the third & fourth hole on the crank pulley (there's 12 holes total).

Since I know I have valve seating issues I believe it's safe to go ahead and take the heads off at this point and forgo waiting on the leak down tester. At this point point I need to know where the coolant is coming from which I believe will either be the head gasket or a crack in the head and/or block. If it's a noticeable head gasket issue that's one thing, a crack is another matter entirely from what I understand especially with this being the less desirable 5.0.

Thinking out loud here - please correct me if you see any flaws in my thinking.

Ty

 

[Schurkey]

I was able to get some pressure into each cylinder for a rough and dirty test and found definite leakage on the intake valves on #4 and #6.

Some folks will say that if the leakage is low enough, leakage at a valve can be "ok". I disagree. I accept NO audible leakage from either valve, and NO bubbles in the radiator. As said, there WILL be some leakage past the rings, and you need the leakdown tester gauges to quantify that.

I found TDC for each cylinder by first finding #1 TDC by aligning the engraved line on the crank pulley up with the notch on the timing chain cover. Made sure each rocker arm would wiggle around a bit (otherwise you're at BDC).

No. Not BDC. TDC Compression, or TDC Exhaust (overlap.) TDC Compression, both valves are closed. TDC Exhaust, both valves would be open on overlap unless the lifters have bled-down enough that one or both valves close.

If I hear a valve leak during the leakdown test, I'll pull the valve cover and pop the valve with a rubber hammer. Jolting it open and allowing it to slam shut sometimes crushes the carbon that's keeping the valve slightly open, allowing it to seal.

Don't hit the retainer, hit the valve tip directly, or the valve end of the rocker arm--but don't allow the pushrod to drop out-of-place.

Then if you rotate 90 degrees you're at TDC for the next cylinder in the firing order, in this case #8. I determined 90 degrees by advancing to the middle spot of the third & fourth hole on the crank pulley (there's 12 holes total).

I need a picture to visualize it. To me, if there's 12 holes, and four planes on the crankshaft, the planes are 3 holes apart, not four. 12 / 4 = 3

Since I know I have valve seating issues I believe it's safe to go ahead and take the heads off at this point and forgo waiting on the leak down tester.

Wouldn't be my first choice. I'd want to know how much leakage there is past the rings, and the only way to know is to watch the gauges. The noise echos around the crankcase, can sound like a big leak but actually be small. Or sounds like a small leak, but is actually large. The gauges tell the real story.

Hoping this is a head-gasket leak...but it sounds like you'll be getting the valves and seats lapped or more-likely ground/cut, and be sure to inspect the valve guide-to-valve stem clearance.

 

[L31MaxExpress]

I was able to get some pressure into each cylinder for a rough and dirty test and found definite leakage on the intake valves on #4 and #6. Aside from that I can hear air moving regardless but with the intake off and my method of shoving an air guns rubber tip into the hole that's all I can for sure say was happening.

The following is a check for operator error on my part as well for the next guy that possibly comes along:

I found TDC for each cylinder by first finding #1 TDC by aligning the engraved line on the crank pulley up with the notch on the timing chain cover. Made sure each rocker arm would wiggle around a bit (otherwise you're at BDC). Then if you rotate 90 degrees you're at TDC for the next cylinder in the firing order, in this case #8. I determined 90 degrees by advancing to the middle spot of the third & fourth hole on the crank pulley (there's 12 holes total).

Since I know I have valve seating issues I believe it's safe to go ahead and take the heads off at this point and forgo waiting on the leak down tester. At this point point I need to know where the coolant is coming from which I believe will either be the head gasket or a crack in the head and/or block. If it's a noticeable head gasket issue that's one thing, a crack is another matter entirely from what I understand especially with this being the less desirable 5.0.

Thinking out loud here - please correct me if you see any flaws in my thinking.

Ty

DId you tap the valve tips with a rubber mallet on the offending cylinders? Sonetimes it is just crud keeping them from sealing. When you tap the stem, it blows the crud out and they seal up.

 

[L31MaxExpress]

Some folks will say that if the leakage is low enough, leakage at a valve can be "ok". I disagree. I accept NO audible leakage from either valve, and NO bubbles in the radiator. As said, there WILL be some leakage past the rings, and you need the leakdown tester gauges to quantify that.


No. Not BDC. TDC Compression, or TDC Exhaust (overlap.) TDC Compression, both valves are closed. TDC Exhaust, both valves would be open on overlap unless the lifters have bled-down enough that one or both valves close.


I need a picture to visualize it. To me, if there's 12 holes, and four planes on the crankshaft, the planes are 3 holes apart, not four. 12 / 4 = 3


Wouldn't be my first choice. I'd want to know how much leakage there is past the rings, and the only way to know is to watch the gauges. The noise echos around the crankcase, can sound like a big leak but actually be small. Or sounds like a small leak, but is actually large. The gauges tell the real story.

Hoping this is a head-gasket leak...but it sounds like you'll be getting the valves and seats lapped or more-likely ground/cut, and be sure to inspect the valve guide-to-valve stem clearance.

I still say it is with 99% probability an intake gasket leak in my experience, having had one explode on startup from the same thing.

 

[Schurkey]

I can't argue that. I would, however, expect to see a "clean" path where the hot coolant flowed from the coolant crossover in the intake manifold into #1 intake port; and I'd expect to see the evidence of hot coolant "steam-cleaning" the intake port. But the photos don't show the floor of the port, only some of the roof.

Another reason to use the leakdown tester--if he pressurizes the cylinder for a minute or five and can find no bubbles in the radiator, the likelyhood of the coolant passing by the intake gasket increases. I'd think a big leak like he has would show up under ~100 psi if it were a gasket, and maybe even if it were a cracked casting. Not guaranteed...but likely.