Toyota Tundra Forums banner

1 - 20 of 97 Posts

·
Premium Member
Joined
·
387 Posts
Discussion Starter #1
A leakage test (as opposed to a compression test) is faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body would point to a leaky intake valve. Air coming out of the PCV valve fitting would tell you the rings and/or cylinders are worn.

With that being said here are the results:

Cylinder 1 = 5%
Cylinder 3 = 35%
Cylinder 5 = 37%
Cylinder 7 = 23%

The Toyota Specifications for the Leak Down Test seem very high.
30% leakage = engine in great condition
50% leakage = still in pretty good condition
60% leakage = trouble

I have searched the internet for info, but, these numbers always come up.
5 - 10% leakage = engine in great condition
Up to 20% leakage = still in pretty good condition
More than 30% leakage = trouble

I am very shocked that the Toyota Specifications are so extreme i.e. 60% leakage for any work to be implemented.
Toyota Canada only wanted the driver’s bank done.
I assumed wrong in thinking that they would have done both banks to be thorough.


Can anyone else verify if Toyota's Leak specs. are correct?
 

·
Registered
Joined
·
848 Posts
who did the leakdown test? what is the reason for the test? just to check it or are you having engine problems? if you think your having engine problems and toyota did the test MAKE them list the leakdown #'s in your recipt so later if you have a problem (even if its after the warrenty is over) they will have to cover it because you already show the problem was exzisting while still under warrenty


its nice to see people are learing that a leakdown test is far superior of a test on a motor then a compression test ..
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #3
I have had countless of misfires since the TRD SC install. The Dealership is still trying to figure out what is causing my intermitent misfires at wide open throttle.
 

·
Premium Member
Joined
·
2,395 Posts
Up to 30% leakdown at the rings of a mass produced engine is actually great and I would say 40% is where it gets questionable. 50% would be acceptable at higher mileage as long as there's no noticeable oil consumption. What also really matters is the balance between cylinders and not so much the average leakdown. If Toyota runs a considerable end gap on the top rings, the numbers will show this even though the engine is in great shape. I would think Toyota would set some safety margin in ring end gaps if they felt comfortable running the TRD blower on this engine. Another thing to consider is in which position the piston was sitting during the leakdown test - you'll always have a very slight taper and difference in surface finish of the overall cylinder wall. Considerable deviation in leakdown numbers from cylinder to cylinder can cause misfiring detectable by Toyota's nazi ECM, but we're talking about 25-30% differences here. I would do the leakdown test with the engine still warm (but not hot) due to the fact that a stone cold engine will yield worse numbers. Ideally it would be best to check your engine at close to operating temp, but that's going to be hard to do, not to mention you'd be jeopardizing your spark plug threads.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #5
thumbster Re: ENGINE LEAKDOWN TEST on my 5.7
I have been on the internet for a couple of hours trying to confirm their numbers, but I can not.
I assume top dead center for the test because that is where you will make most of your power,and I also assumed engine was close to operating temp. for test.

They are now suggesting new rockers, since they have already replaced the lifters.
I wounder if they could tap the rocker tips with a plastic hammer to stop the leakage somewhat?
 

·
Registered
Joined
·
848 Posts
sounds like they are going in the right direction but with the misfire i would bet they will end up doing a valve job or replacing the whole motor before they fix the problem .. rockers wont solve the problem but i am betting that their district manager wants the cheapest things done first so they dont eat the whole engine this is what i dont like about toyotas warrnety service
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #7
thumbster Re: ENGINE LEAKDOWN TEST on my 5.7
This is another test I suggested to the Dealership, but I am not sure if it is even relevant.
Engine Blowby Test
This is a brief statement for people that want info.
Piston rings seal the combustion chamber and prevent engine Blowby, but no set of rings can totally prevent some pressure loss past the pistons. Blowby also dilutes the oil in the crankcase with fuel and combustion by-products, which can shorten the life of the oil. It will also increase crankcase emissions and the load on the positive crankcase ventilation (PVC) system.
How much Blowby is normal? For example, a street performance engine that makes around 500 HP. will typically have about 10 cfm of Blowby with conventional piston rings and ring end gap tolerances.

Measuring Blowby allows us to see how well the rings are or are not sealing.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #8
Stripped Honda Re: ENGINE LEAKDOWN TEST on my 5.7

--------------------------------------------------------------------------------
sounds like they are going in the right direction but with the misfire i would bet they will end up doing a valve job or replacing the whole motor before they fix the problem .. rockers wont solve the problem but i am betting that their district manager wants the cheapest things done first so they dont eat the whole engine this is what i dont like about toyotas warrnety service
I am running out of patience, it has been a year.
 

·
Premium Member
Joined
·
1,142 Posts
Hot or cold makes a huge difference. Did they oil down the cylinder before test?

Position of the slug in the hole making significant difference can be a sign of bore damage.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #10
RIjon Re: ENGINE LEAKDOWN TEST on my 5.7

--------------------------------------------------------------------------------
Hot or cold makes a huge difference. Did they oil down the cylinder before test?

Position of the slug in the hole making significant difference can be a sign of bore damage.
I am sure the Master Tech. performed the procedure properly, but these are some of the questions I am asking via e-mail on Monday.
 

·
Registered
Joined
·
117 Posts
What's the basic compression on each cylinder? If high and even you wouldn't get any misfires. I driven vintage Toyotas that had a 20 PSI differential between cylinders and they still wouldn't misfire at wide open throttle, just had a wee bit of roughness. I suspect you have some kind of ignition or lean fuel mixture issue.

How did you determine TDC on each cylinder when performing the leakdown? It's easy to put cyl#1 at TDC, but not on the others. So if you (or the Mastertech) were off a bit you'd get more leakage.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #12
ggemigniani Re: ENGINE LEAKDOWN TEST on my 5.7

--------------------------------------------------------------------------------
What's the basic compression on each cylinder? If high and even you wouldn't get any misfires. I driven vintage Toyotas that had a 20 PSI differential between cylinders and they still wouldn't misfire at wide open throttle, just had a wee bit of roughness. I suspect you have some kind of ignition or lean fuel mixture issue.

How did you determine TDC on each cylinder when performing the leakdown? It's easy to put cyl#1 at TDC, but not on the others. So if you (or the Mastertech) were off a bit you'd get more leakage.
The compression range is 195 - 205. Sorry, I did not ask the number for each one.
The TDC question is being asked also, via e-mail
 

·
Registered
Joined
·
2,792 Posts
What's the basic compression on each cylinder? If high and even you wouldn't get any misfires. I driven vintage Toyotas that had a 20 PSI differential between cylinders and they still wouldn't misfire at wide open throttle, just had a wee bit of roughness. I suspect you have some kind of ignition or lean fuel mixture issue.

How did you determine TDC on each cylinder when performing the leakdown? It's easy to put cyl#1 at TDC, but not on the others. So if you (or the Mastertech) were off a bit you'd get more leakage.
+1
You need real low compression to cause a misfire. If you have a compression problem causing a misfire, it's not going to happen at WOT only.
Most high rpm misfires that are strong enough to set the code are going to be from a spark plug.
Is this a WOT misfire or a high RPM misfire or both?
Have you tried installing spark plugs that are one heat range hotter?
If your misfire is under partial load like climbing as hill at 30-50% throttle, I think you have spark leaking to ground rather than through the plug. Spark could be jumping from the coil connections or the plug connections to the head inside the spark plug tube. Did they seal the connections with dielectric grease?
If you are leaning out enough to misfire, you will set a lean condition code. I doubt you have this issue. All the tundras I've seen run pretty rich throughtout the rpm band.
When exactly does it misfire?
And, can you feel it misfire?
Is the misfire a multi-cylinder misfire, or do you get a specific cylinder misfire?
Sometimes a misfire code can be triggered by other things. Early OBDII chrysler minivans could set a misfire code with a stiff place in the serpentine belt. TSB stated that a new serp belt would cure them. I just want to be sure that you actually have a misfire. I haven't been following your problem.
 

·
Registered
Joined
·
117 Posts
The compression range is 195 - 205. Sorry, I did not ask the number for each one.
Those numbers are well within factory specs so the cylinders are sealing good and the cause of the misfire can't be compression related. Toyota factory repair manual don't have cylinder leak down specs.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #15
socal57chevy Re: ENGINE LEAKDOWN TEST on my 5.7
Have you tried installing spark plugs that are one heat range hotter?
Upgraded plugs are included in the SC Fit Kit.
TRD Gap = 0.032"
Stock Gap = 0.0394" - 0.0433"

Is this a WOT misfire or a high RPM misfire or both?
Both

When exactly does it misfire?
It will happen at anytime, no common symtoms, and plus it is intermitent.
Only thing common when it does happen is WOT and high RPM (always first gear).


Is the misfire a multi-cylinder misfire, or do you get a specific cylinder misfire?
Cylinders 1,3,5,7 have all rang in as misfire codes.
Cylinder 1 has been the only one to come in, the last 7 times.



ggemigniani Re: ENGINE LEAKDOWN TEST on my 5.7

Those numbers are well within factory specs so the cylinders are sealing good and the cause of the misfire can't be compression related. Toyota factory repair manual don't have cylinder leak down specs.
You have a manual? So did it cost you $15.00 (TIS Website)? Thanks for looking it up, very much appreciated.
 

·
Registered
Joined
·
2,792 Posts
Move the #1 spark plug to a different cylinder. If the misfire follows the spark plug, it is the cause of your misfire.
If the misfire stays at the #1 cyl, move the coil to a different cylinder. If the misfire follows the coil, it is the source of the misfire.
If the misfire remains at #1 cyl, move the connector that supplies spark from the coil to the plug to a differen cyl. If the misfire follows, it is your problem.
I would bet that your problem is a spark plug since it is at high rpm WOT. Just because the plugs are new, does not mean they are good. They could also have minute cracks allowing spark to leak. My money is on the spark plug/plugs.
You might also want to check the coils for cracks since they were recently removed and reinstalled.
Just an added bit of info, the upgraded plugs with the S/C kit are a colder heat range to handle the increased cylinder pressures from the S/C.
 

·
Premium Member
Joined
·
2,829 Posts
I am almost positive that it has to do with fuel pressure regulators (Toyota have cheap ones and I ended up with similar issue on mine)

Each side of that engine have fuel pressure regulators and on mine I had similar misfire issue cyl 1,3,5, and sometimes 7 (anything after 4000 rpms). It took for ever to find that problem.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #18
socal57chevy Re: ENGINE LEAKDOWN TEST on my 5.7
Work Done Already:
-new plugs
-swapped coils and injectors
-checked valve clearances
-pressure 195-205 Psi
-new hydraulic adjusters (lifters)
-checked MAF & intake
-new ECU
-swapped VVT Valves

This is from an old thread, but thanks for your input.


Crazy Ivan Re: ENGINE LEAKDOWN TEST on my 5.7

--------------------------------------------------------------------------------
I am almost positive that it has to do with fuel pressure regulators (Toyota have cheap ones and I ended up with similar issue on mine)

Each side of that engine have fuel pressure regulators and on mine I had similar misfire issue cyl 1,3,5, and sometimes 7 (anything after 4000 rpms). It took for ever to find that problem.
Thanks for your input.
 

·
Premium Member
Joined
·
2,395 Posts
I also think it's a fuel problem and am willing to bet my hat that's what's causing your misfires. Based on what's already been tried, everything is pointing towards the driver's side cylinder bank going lean due to lack of fuel. Since you're getting more cyl #1 misfire codes (farthest cyl from the fuel inlet), it's a good indication there's not enough fuel pressure or volume in that fuel rail. Like Ivan said before, some Toyota V8s use two fuel pressure regs (one per bank) and there may be a problem with the driver's side reg. I'm however not certain the 5.7 uses two pressure regs, so I can't say for sure.

BTW - in terms of ignition control, cylinders are banked via the ECU in two groups (cyls 1,4,6,7 and 2,3,5,8). This is in reference to timing control and the purpose of grouping them in this manner is to cross interpolate with the four knock sensors. This allows the ECM to figure out exactly which cylinder is knocking and control it accordingly.

socal57chevy said:
You need real low compression to cause a misfire. If you have a compression problem causing a misfire, it's not going to happen at WOT only.
Absolutely the truth - I don't for one second think the problem is related to low compression or overall mechanical engine condition.
 

·
Premium Member
Joined
·
387 Posts
Discussion Starter #20
The 5.7 only has 1 press. regulator, and it is located on the passenger side.
 
1 - 20 of 97 Posts
Top