2.4 D.I. Engine Rebuild - TerrainForum.net: GMC Terrain Forum
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post #1 of 9 (permalink) Old 11-02-2019, 07:05 PM Thread Starter
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2.4 D.I. Engine Rebuild

I rebuild Ecotec engines here in Las Vegas and was wondering if you fellow board members could answer a few questions for me. Usually my customers bring me 2.2 or 2.4 engines with failed timing chains that require cylinder head repair and timing set(s) replaced. The next most common issue is a rod knock from low oil needing a complete rebuild. Recently I have been getting several requests for full engine rebuilds on the 2012-2016 2.4 direct injection power plants. Dealership telling owners $7500+ for the service. All stemming from low oil damaging engines. Some are "mild" rod knocks and others have seized or locked up.

I am unaware why some qualify for the extended oil consumption warranty and others do not (the Terrain in my garage started out as a rental so automatically denied extended consumption warranty. Anyway my question is for any of you that have had the warranty repaired completed. Did the updated pistons cure the oil consumption issue? I have read TSBs that claim its the direct injection washing down the bores and I have read TSBs that claim its the piston. I ask because I want to correct the issue as well when I do the work. If the updated pistons are a cure (or big improvement) great I will sell OEM and have shop hone bore only. If not, I will have bored .020 and replace pistons (aftermarket as OEM is standard only). If the new pistons are magic and truly cure the issue, I will offer to re-sleeve block for customer and not bore ($$$ is new issue). Labor (except on re-sleeve option) stays the same cost by me, but I like to offer all parts options with pros and cons. At this point I simply do not have the data to offer advice.

The Terrain I am doing now was originally a rental vehicle and purchased by the family that brought to me. Rod knocking, top chain guide missing upper rail, side guide in 3 pieces, oil down 3 quarts and way over due for a change. Crankshaft was able to polish and use standard bearings for both rods and mains. Bores looked amazing. All hash marks looked perfect despite oil usage and low amount. Machine shop confirmed bores well within spec so factory updated pistons are going back in. Cylinder head got a full refurbish including valve job, seals, and milled. All 16 guides were still good. This is very rare, usually at least the exhaust guides need replaced ( or at least on the non-direct injection Ecotec engines. The valve lash adjusters (lifters) were another story. 7 of the 16 were failing or had already seized completely. I am replacing all 16 to be safe (aftermarket for cost savings and prior use know to be good). Also replacing all 4 injectors, pump and fuel pipe to rail.

This, being my first D.I. project is a learning curve as well as knowledge gained to future rebuilds. I will have all parts from shop and dealership on Monday and begin the rebuild/install process and can update every few thousand miles to the oil usage, assuming customer will stay in touch as requested.

Also should mention vehicle has 130K. I used Hastings rings. I feel they are as good as (if not the actual manufacturer of) factory rings. On several HHR, Auras, and Malibu rebuilds I have done in the past, simply replacing pistons with cheap aftermarket and Hasting rings really improved oil usage. So I am optimistic that the updated factory pistons will do so as well.

So thanks for reading and post any input you have towards the oil usage issue, love to know.

Las Vegas NV
Rebuild Ecotec engines
Repair GM cars & SUVs
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post #2 of 9 (permalink) Old 11-02-2019, 10:55 PM
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Had the warranty repair for the rings done at 50k for oil consumption (after the timing chain was replaced at 25k). Now at 109,000 and the oil consumption has not returned.

2012 Equinox 2.4L 1LT AWD, black, 80,000 miles
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post #3 of 9 (permalink) Old 11-02-2019, 11:23 PM Thread Starter
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Thanks for the reply. You say they replaced the rings, did they replace the pistons as well?

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post #4 of 9 (permalink) Old 11-03-2019, 03:07 PM
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My 2012 Nox was serviced last December after 90k. The timing chain slipped at 87K, no damage, replaced under a Route 66 Warranty. It was previously owned and unknown quality of service. Oil analysis showed more than 5% fuel dilution in the oil after 1500 miles. Dealer replaced HP fuel pump. No difference. I assumed fuel dilution was due to high blow-by along with oil consumption. No change to fuel dilution after pistons and rings were replaced and adequate time to seat. Oil consumption was slightly over 1 qt/every 1000 miles. Cut off for GM is 1qt/2k miles, under 120k total miles. They said they would warranty again if it occurs before that mileage.

I am not convinced that the sole problem with oil consumption was due to rings and pistons in certain years. GDI is big factory in the accelerated wear to cylinder walls, and timing chain wear/slippage. My cylinders lost all the cross-hatch, and showed minor pitting likely due to fuel wash and hot spots. Dealer refused to check cylinder specs. My compression and leak down was nearly the same before and after (220-225, <5%) Engineers have discovered better methods of fuel delivery, atomization and improved flame kernal propagation with DI and to limit cylinder wash in the past ten years. Unfortunately, that technology is not in use in these Gen II engines.

Another reason I doubt the ring and piston defect causing wear and subsequent oil consumption is based on data from BlackStone labs. They gave me oil sample data for 500 different GM Ecotec engines from 2006 - 2017. After analyzing the data and running various scenarios on those data points, GDI Gen II engines showed double the iron wear rate in the oil compared to non GDI engines. Chromium has elevated levels as well compared to same non GDI engines. Wear rates increased significantly at or above 2-3% fuel dilution. Fuel Dilution above 2% was non-existent in port injected engines and typically much lower. Those engines are known to last over 200k. My own oil analysis for the past year, shows concentrations of fuel at low mileage, and viscosity shearing and additive depletion at 2500 miles. By 3500 miles the oil is 5W-20, boron additves depleted by 80%, and beginning of increased wear rates. I even ran Amsoil Sig Series 5W-30 which dealt with the fuel contamination using high initial levels of boron. My next step is get the fuel injectors replaced to see if that reduces the accumulation of fuel contamination.

Another contributing factor is the Oil Life Monitor that people rely on too much. GM updated them in 2013, but many on the road still have the old calibrations. People do not check oil level at every fill up as their owner manual recommends. The quality and type of oil is a factor. Some owners are content with cheap quick lube service and wait for the OLM to service it. Many reports of customers coming for VVT issues, and reduce power symptoms to find they are 3qts low.

The PCV system design is another problem. It uses a fixed orifice in the head and poorly design clean side pipe and non-baffled separator in the intake housing. The fixed orrifice is minimally affective at idle but at cruse and light loading, vacuum in the intake/crankcase nearly drops to zero, and pushes moisture and oil out the clean side where is collects and freezes. Same for the fixed orrifice. Stop and go driving in any condition there is no accumulation of moisture or blow-by products, but at cruising speed in lowe temps, higher humidity, I get a noticeable amount of moisture and oil on the clean side. High crankcase pressured leads to rear engine seal failures, dumping the contents of the crankcase on the pavement in a few moments. I am looking at redesigning my PCV system, eliminate the orrifice and go with an adjustable, external PCV valve.

My recommendations: use a high quality 100% synthetic oil, and quality filter, change every 3k miles, have oil tested once a year to keep tabs on fuel dilution. Try a 40W oil if fuel keeps diluting and shearing the viscosity. Change oil after 1st 1k miles to reduce wear metal contamination. Use a catch can on the clean side of the PCV. Easy install, This keeps half of the system clear and prevents both sides from freezing, and blowing seals, and reduces intake valve build-up. From the BMW forum, they also have trouble with PCV design, they recommend adequate warm ups before driving in freezing weather, daily italian tune-ups.

When rebuilding the engines, I agree with inspect the exhaust valves and exhaust manifold. The local machine show often see pitting on the exhaust valves. I had significant pitting on mine, so I had them re-cut, replace the valve stem seals is a given. They come with the GM kit. They wont replace them at the dealer even though that is one of possible causes in the TSB. The exhaust manifold often cracks between the ports 2-3. Do good job cleaning the oil sump, and valve cover baffles.

Cloyes offers an improved timing chain set, tensioners and metal guides, as they report. A company out east has done high temp coatings on pistons, combustion chamber and valves for the ecotec to reduce the effects of carbon build from GDI engines. I believe newer engine designs are incorporating this technology. Something to consider for customer that want the extra mile. On mine, I have installed 6mm vacuum ports on each runner at the intake manifold for injecting CRC cleaner directly into the intake ports. The stock intake was not designed to flow fluid that well.

It appears oil consumption is stable on my piston/ring replacement. In some cases I have read, fuel replaces the burned oil up to a point giving a false oil level Waiting on my next oil analysis.
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post #5 of 9 (permalink) Old 11-03-2019, 07:19 PM Thread Starter
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Thanks for that detailed reply. If you are losing a quart in 1000 miles that should satisfy the requirements for the warranty claim, right? In your situation, I am wondering if they will replace the engine instead of rebuild. Please post what the outcome is.

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post #6 of 9 (permalink) Old 11-03-2019, 07:56 PM
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Quote:
Originally Posted by uluz2a6 View Post
Thanks for that detailed reply. If you are losing a quart in 1000 miles that should satisfy the requirements for the warranty claim, right? In your situation, I am wondering if they will replace the engine instead of rebuild. Please post what the outcome is.
The work was completed last December. They entered my Nox into their monitoring program and immediately scheduled replacement of the rings and pistons as soon is it hit their threshold. Had it back in 2 days and they gave a loaner car. When I showed them the glazed cylinders and pitting, they still would not budge. They will only replace the engine if cylinders are damaged and approved by HQ. They do the replacement in the car so honing the cylinders and cleaning was out of the question. All they do is swap or replace. So far no more oil consumption I assume after 11k miles, I have been changing oil every 2-3k miles due to fuel contamination.
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post #7 of 9 (permalink) Old 11-03-2019, 11:04 PM
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Thanks for that detailed reply. If you are losing a quart in 1000 miles that should satisfy the requirements for the warranty claim, right? In your situation, I am wondering if they will replace the engine instead of rebuild. Please post what the outcome is.
Here is a link to an article about Dickmeyer Auto Engineering that solved GDI carbon build up and PCV clogging issues.

https://www.enginebuildermag.com/201...-fictions-gdi/
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post #8 of 9 (permalink) Old 11-06-2019, 08:06 PM
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Yes, piston and rings. If you poke around on here I think you should be able to find a link to the GM service bulletin on this, which describes why the cylinders are fine, even if they show zebra striping, etc. might be useful reading for you.

Also, FYI I have gone by the OLM, usually changing it around 0-10%, but with full synthetic.

2012 Equinox 2.4L 1LT AWD, black, 80,000 miles
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post #9 of 9 (permalink) Old 11-08-2019, 02:05 PM
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uluaz2a6,

Hopefully you will share your findings, your knowledge learned and pictures of gdi equinox and terrain GDI engines with us as you do rebuilds.

Answering your original question,
both rings and piston are replaced under GM warrantee, according to gmTechlink. (see below)

Your other question is not known for certainty
But I have read of folks who have had the piston and rings replaced, only to have the oil consumption issue return
And
I believe Oil consumption still occurs on newer engines that were built with new piston and rings
.... all gdi engines will burn oil eventually unless ....

Xxxxxxxxxxxxxxxx

Gdi engines suffer from carbon build up on intake valves, as explained by Mr. Dickmeyer, in sydnesb's above link.

GDI Design Flaws
it’s almost like the crankcase ventilation system was an afterthought.
“On the EcoTec GM 2.4L engine, the inlet where the plastic intake manifold meets the heads for the crankcase ventilation system
is down in a low spot
that you would normally see an oil drain back passage through,”
“So you get oil that as it works its way through the engine and comes up to the top end and then works its way back down and falls to these low spots.
That’s where .... the vacuum source for the crankcase ventilation system, so they’re sucking in oil.

"“We coated the backsides of the valves,”
“I then added an oil separator to the intake system
and
we coated the entire skirt of the pistons with PTFE moly coating.
We coated the top and the underside with a heat barrier
and at 40,000 miles we pulled the intake manifold off this vehicle and there was little to no build up.
^^^^^. Mr. Dickmeyer^^^^^

Since the PCV is internal to engine, I don't know how Mr. Dickmeyer added an oil separator (catch can) to the internal PCV orifice ......
Unless he plugged up the internal 80 thousands of an inch diameter internal PCV orifice in the intake manifold
And
add a new hole in top of crankcase, and a new PCV orifice, with an external hose, a catchcan and then a new hole "somewhere" to return the crankcase gasses to the intake manifold or intake ports .....
( that ^^ is a good idea for you)
And
while I understand coating of valve stem and top side of intake valve with "teflon" , but pistons
And inside of engine part-of-the-valve with an heat insulator? (What is heat resistant coating flakes off
((same with the teflon coating)), would it trash cat converter, jam in piston rings? Who knows?)
Xxxxxxxxxxxxxxxxx

Since a theory is that carbon falling off intake valves, via LSPI, scratches cylinder walls,
during your tear downs and rebuilds, could you carefully examine cylinder walls for scratches, which might allow piston blow by and oil consumption.
Or is it actual grooves in pistons, into which rings attach that is damaged by carbon and then allows piston blowby ?
Who knows?

Also, in the oil control rings, are the tiny holes , are those plugged up with carbon or gunk?
Let's us know your observations

xxxxxxxxxxxxxxxxxx
FYI
Around here, where we have temperatures around 10 degrees F in winter and colder, these engines suffer from crankshaft rear main seal failures. The plastic nylon orifice of the dirty side PCV inside the engine, plugs up, bonds with the engine oil sludge, (like varnish on metal?) coupled with piston ring blowby,
Pushes crankcase gunk up and out the clean side PCV breather hose, and if cold enough, it freezes solid...
Then,
with enough crankcase pressure from piston blowby
a hole is blown thru viton rear main seal at sharp corner where living hinge attaches to overmolded steel ring.
Yes a hole, and then catastrophic failure as engine oil is squirted onto pavement

(Are aftermarket rear main seals a better quality?)

The Mr. Dickmeyer external Dirtyside PCV with catchcan idea, should prevent crankshaft rear main seal failure

Xxxxxxxxxxxxx

Not much is known of the specifics of the 5-25-2013 running change piston ring upgrade
.... Below is from gm techlink.....

2.4L Ecotec Engine Oil Consumption
August 6, 2013
Excessive oil consumption on some 2010-2013 LaCrosse, Equinox, Terrain and 2011-2013 Regal models equipped with the 2.4L engine (RPOs LAF, LEA) does not require engine replacement. If excessive oil consumption is confirmed after an oil consumption test, new pistons and piston rings should be installed.

Piston Ring Coating
The top compression ring in the new kit has a more robust coating on it that is designed not to wear as quickly as the original coating. Tests indicate that it wears about 4-5 times longer than the original coating.

If the top compression ring is worn, it will allow combustion pressure past it, which causes the oil control rings to be less effective and results in excessive oil consumption.

On 2010-2011 vehicles built before March 2011, there is a strong correlation between leaking high pressure fuel pumps diluting the oil and causing the ring wear. Due to this, check the fuel pump, balance chain, balance chain tensioner and timing chain for the proper part numbers. The updated fuel pump has an enhanced seal.

If these updated parts have not been installed during a previous repair, they should be replaced when the pistons and rings are replaced. Use field action #12313 if the balance chain and/or fuel pump is replaced.

Zebra Stripes
The pistons must be replaced because as the rings wear down, it starts to widen the piston ring groves. The worn grooves will not retain the new rings correctly.

The “zebra” stripping on the bore surface (Fig. 1) is not an indication of a cylinder bore abnormality, but rather a transfer of the ring material as it was worn down. The bores are still uniform and the new rings seal. The validation of the new ring pack was done on used blocks that had zebra striping. It’s not necessary to do any surface treatment to the zebra striped bores when installing the new pistons and rings.
^^^^^ techlink_aug_f01. ^^^^^

To be clear,
zebra stripes is different then combustion chamber wall scouring. Combustion wall scouring occurs when carbon from GDI intake valves falls into combustion chambers and scratched cylinder walls.
Zebra stripes is the transfer of piston ring plating to the cylinder walls.


My 2 cents ^^^^^

2012 Traverse with Elite E2 X catchcan
Three Equinox with 2.4 engine, 2013, 2016 and 2016
2017 equinox with 3.6 engine with Elite E2 X catchcan

Last edited by ThreeNox; 11-08-2019 at 02:11 PM. Reason: Typo 's
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