Valve cover gasket replacement on 4.2L

dmtaurus

Original poster
Member
Jul 1, 2012
42
I got some oil in #3 spark plug well so the infamous gasket is beginning to leak. I read a post that talks about the valve cover gasket and how to change it. It has good detail but one thing I didn't read was anything about the 2 hoses that wrap around valve cover at the firewall end of the valve cover. I noticed on my 06 that these 2 hoses run in front of the last intake manifold bolt that is at the firewall end. What are these hoses? From a quick look they appear to be heater hoses. That last bolt on the intake looks like a pain to get at and even more so with hoses running in from of it.

Also, I got GB remanufactured fuel injectors to replace the originals as preventative maintenance, since I'm going to be working there. Are the injectors a pain to replace? Seems like removing the rail hold-down bolts and a little back and forth rolling of the injector rail would be the only thing needed to get them out.
 

CaptainXL

Member
Dec 4, 2011
2,445
dmtaurus said:
I got some oil in #3 spark plug well so the infamous gasket is beginning to leak. I read a post that talks about the valve cover gasket and how to change it. It has good detail but one thing I didn't read was anything about the 2 hoses that wrap around valve cover at the firewall end of the valve cover. I noticed on my 06 that these 2 hoses run in front of the last intake manifold bolt that is at the firewall end. What are these hoses? From a quick look they appear to be heater hoses. That last bolt on the intake looks like a pain to get at and even more so with hoses running in from of it.

Also, I got GB remanufactured fuel injectors to replace the originals as preventative maintenance, since I'm going to be working there. Are the injectors a pain to replace? Seems like removing the rail hold-down bolts and a little back and forth rolling of the injector rail would be the only thing needed to get them out.

Most of us for the most part have a leak or two where valve cover seals the spark plug well. However the leak is such a small amount that it doesn't make sense financially to take apart what you said.

If you decide to proceed then you have quite a project ahead of you. I would recommend an ultrasonic injector clean and balance instead of new injectors. You will save some money. Injectors are rated to last the life of the truck (billions of cycles). Kind of a waste of money to put new ones in.
 

dmtaurus

Original poster
Member
Jul 1, 2012
42
CaptainXL said:
Most of us for the most part have a leak or two where valve cover seals the spark plug well. However the leak is such a small amount that it doesn't make sense financially to take apart what you said.

If you decide to proceed then you have quite a project ahead of you. I would recommend an ultrasonic injector clean and balance instead of new injectors. You will save some money. Injectors are rated to last the life of the truck (billions of cycles). Kind of a waste of money to put new ones in.

The leak is enough that it made black with greasy oil, which turns somewhat to carbon and allows dielectric failures, the porcelain of the plug, and even migrated around the spark plug threads and onto the end of the spark plug. Now, the plug was tight in the cylinder head but multiple heating/cooling cycles could possibly make this oil migration occur. Given that #3 and #5 were the wells that had oil residue, #3 being the worst with the most oil, it would be expected that others may soon fail and that oil residue could accumulate even more so. Catching this before it becomes a spark misfire, to me, makes sense, especially when it's summer and not a wintertime mess to work on.

Second, as far as the injectors are concerned I did have some excess fuel in cylinder #1 after I did an injector clean with my OTC fuel injector canister using OTC intake manifold decarb cleaner and OTC fuel injector cleaner. This condition seems to have cleared up after running for several hundred miles. Nevertheless, while I'm there why not pay a little now and ensure that another 92000 miles are relatively trouble-free? A dumb thing that was done on these trucks was the removal of the fuel filter. The only fuel straining I see being done is the strainers inside the injectors.

Third, I've read where guys have removed intake manifold bolts and found that several were just snug. An intake leak isn't good and a few dollars spent on the so-called improved Fel-Pro gaskets sounds like a good idea.

BTW, superior blue is a really good color on these trucks.

So, getting back to my original questions are the 2 hoses heater hoses? And are the injectors relatively easy to remove?
 

Envoy_04

Member
Jul 1, 2013
749
Don't know anything about the ease of removing the injectors but I can tell you about the hoses. They are the secondary air injection system (smog pump) hoses. One intake and one return hose. They go from over by your air box and exhaust manifold around the back of the head, then turn under and terminate at the pump which is on the frame rail almost directly under the driver's seat. Mine turn to a plastic section of pipe behind the head and on each end they've got funky pressed in clamps that can be undone, but not without ruining them. You'll need new clamps when you put the houses back on, regular hose clamps would work fine, the only thing the lines have in them is air.
 

Jtyler77

Member
Aug 10, 2013
44
dmtaurus said:
I got some oil in #3 spark plug well so the infamous gasket is beginning to leak. I read a post that talks about the valve cover gasket and how to change it. It has good detail but one thing I didn't read was anything about the 2 hoses that wrap around valve cover at the firewall end of the valve cover. I noticed on my 06 that these 2 hoses run in front of the last intake manifold bolt that is at the firewall end. What are these hoses? From a quick look they appear to be heater hoses. That last bolt on the intake looks like a pain to get at and even more so with hoses running in from of it.

Also, I got GB remanufactured fuel injectors to replace the originals as preventative maintenance, since I'm going to be working there. Are the injectors a pain to replace? Seems like removing the rail hold-down bolts and a little back and forth rolling of the injector rail would be the only thing needed to get them out.

Did you end up doing your valve cover gasket?
 

dmtaurus

Original poster
Member
Jul 1, 2012
42
Jtyler77 said:
Did you end up doing your valve cover gasket?

Yes, I did; thanks for asking.

It was a very interesting experience. I took some pictures that I hope to at some time post so that they can help others. I used the Haynes manual for help and torque values.

From what I remember these are the steps I did and my observations on doing it.

1. Remove the bolts at each end of the A/C line that runs over the valve cover. Contrary to what Haynes says, the line DOES NOT need to be removed and the A/C system drained to remove the valve cover. I found that there is plenty of clearance to remove the cover, but be careful when moving the hose so as not to strain the connections at the ends of the hose.

2. Remove the drive belt. Pretty straightforward and easy to do.

3. Remove the intake plenum, the air intake hose, the air injection hose, the throttle valve body, and the air box cover.

4. Disconnect the fuel line. See Haynes for details.

4. Remove the alternator. It takes 3/8" drive metric sockets and u-joints and extensions to remove the bolts. Make sure to have a variety.

5. Remove the electrical connectors that surround and are on top of the valve cover.

6. Disconnect the 3 electrical connectors from the PCM. They have flip-up gray levers. Remove the PCM.

7. I found the air injection hoses to be mounted to a bracket that looks like is held to the back of the cylinder head with a bolt. The bracket on mine was loose which allowed the bracket to wobble. This made it easy to eventually remove the intake manifold. I did not have to cut clamps or hoses.

8. Remove the intake bolts. The bolts are retained to the intake manifold. At least GM did that right. Use an inspection mirror to help guide the socket to the bolts; they are hard, if not impossible, to see. Now, the hard one to get is the one closest to the firewall. I was not sure if this bolt was going to come out easily. To get it out I used a 1/4" drive ratchet and metric sockets and extensions to turn it. I say turn because all the bolts, except for the 2 located at the center of the manifold, were finger tight. I could not believe that GM did such a poor job in assembling the engine. These bolts should have been tight; this was the first time that the manifold was removed. I am not 100% sure but I didn't see evidence they were sucking air around the gaskets, so I am glad about that. The intake manifold gaskets were really oily; GM should have put a conventional PCV system on this engine instead of the crappy system they did use. I used several cans of carb cleaner on the intake holes and the injector holes to dissolve the oil and carbon.

9. I decided to replace all the injectors because the manifold has to come off to remove the fuel rail and the injectors. Given the miles, and the heating and cooling cycles that I know this engine goes thru, I decided that this was a prudent thing to do. Other people might think different. I used GB injectors from Rock Auto and they fit well. Removing the fuel rail was easy by rocking it up and down. The injector seals on the head side get the heat so that was another reason to do replace them.

10. Remove the spark plug coil packs, the plugs, and finally the intake cover. The intake cover has a couple of kind of hard to get to bolts at the firewall but 1/4" drive sockets and extensions did the job. The gaskets at the plug wells were really stiff from heat and oil, so it was a good thing to replace them and the cover gasket. I used Fel-Pro gaskets because they claim to be improved, and I have had good experience using their products.

11. Reverse the above steps to re-assemble.


Some extra notes:
1. It took me 13 hours to do the job, this being the first time I ever did this job on this engine. On jobs like this one I take lots of time to clean all the parts before re-assembly. That alone took several hours, using Gunk engine cleaner. The time included tool clean-up and put-away.
2. I used a torque wrench on all the bolts except for the alternator and A/C line because I wanted the joints to be right and I didn't want to be doing this job again.
3. Before I reconnected the electrical plugs I sprayed the terminals on each plug with CRC brand QD electrical cleaner.
4. I was worried about finding bolts that were seized in the aluminum head. I had none.

Tools:
1. Get a 1/4" drive torque wrench. It is hard to get to the valve cover and intake manifold bolts, that is if you can get to them when it's all assembled, to do any tightening.
2. Get an inspection mirror, 1-1/2" diameter works good.
3. Get a magnetic pick-up and 4 -prong claw pick-up tool for the bolts and wrenches that get dropped. The Trailblazer has a million holes and pockets where these fall into and I was glad that I could get the wrenches and bolts that got dropped into tight places without all the associated hassle.

Result:
The engine ran really good for a couple of days. Then the engine light lit. It turns out that the variable valve timing solenoid connector plug was still dirty. I cleaned the plug with CRC and that cured that. But in trying to understand how the vvts works, my research showed that it tends to have some filter screens that loosen and fall off. I didn't want that to happen to mine, since the path the oil takes is to the special timing gear on the exhaust camshaft. So I went ahead and got the solenoid from the local Chevy dealer. I thought I'd have to order it but to my surprise he had 3 of them in stock. It appears as though this is a common problem with the 4.2 engine. I specifically bought the GM part since I read stories where the part that was put on was an after-market part, like the Dorman brand, and found to be poorly constructed. I didn't want that hassle so I stuck with the GM part. Turns out that was a good decision because GM did a redesign of the solenoid by putting a retaining spring over the wire screen filters so that they can't fall off.

After all that, the engine runs good and the gas mileage seems to have gone up a little.
 

Jtyler77

Member
Aug 10, 2013
44
dmtaurus said:
Yes, I did; thanks for asking.

It was a very interesting experience. I took some pictures that I hope to at some time post so that they can help others. I used the Haynes manual for help and torque values.

From what I remember these are the steps I did and my observations on doing it.

1. Remove the bolts at each end of the A/C line that runs over the valve cover. Contrary to what Haynes says, the line DOES NOT need to be removed and the A/C system drained to remove the valve cover. I found that there is plenty of clearance to remove the cover, but be careful when moving the hose so as not to strain the connections at the ends of the hose.

2. Remove the drive belt. Pretty straightforward and easy to do.

3. Remove the intake plenum, the air intake hose, the air injection hose, the throttle valve body, and the air box cover.

4. Disconnect the fuel line. See Haynes for details.

4. Remove the alternator. It takes 3/8" drive metric sockets and u-joints and extensions to remove the bolts. Make sure to have a variety.

5. Remove the electrical connectors that surround and are on top of the valve cover.

6. Disconnect the 3 electrical connectors from the PCM. They have flip-up gray levers. Remove the PCM.

7. I found the air injection hoses to be mounted to a bracket that looks like is held to the back of the cylinder head with a bolt. The bracket on mine was loose which allowed the bracket to wobble. This made it easy to eventually remove the intake manifold. I did not have to cut clamps or hoses.

8. Remove the intake bolts. The bolts are retained to the intake manifold. At least GM did that right. Use an inspection mirror to help guide the socket to the bolts; they are hard, if not impossible, to see. Now, the hard one to get is the one closest to the firewall. I was not sure if this bolt was going to come out easily. To get it out I used a 1/4" drive ratchet and metric sockets and extensions to turn it. I say turn because all the bolts, except for the 2 located at the center of the manifold, were finger tight. I could not believe that GM did such a poor job in assembling the engine. These bolts should have been tight; this was the first time that the manifold was removed. I am not 100% sure but I didn't see evidence they were sucking air around the gaskets, so I am glad about that. The intake manifold gaskets were really oily; GM should have put a conventional PCV system on this engine instead of the crappy system they did use. I used several cans of carb cleaner on the intake holes and the injector holes to dissolve the oil and carbon.

9. I decided to replace all the injectors because the manifold has to come off to remove the fuel rail and the injectors. Given the miles, and the heating and cooling cycles that I know this engine goes thru, I decided that this was a prudent thing to do. Other people might think different. I used GB injectors from Rock Auto and they fit well. Removing the fuel rail was easy by rocking it up and down. The injector seals on the head side get the heat so that was another reason to do replace them.

10. Remove the spark plug coil packs, the plugs, and finally the intake cover. The intake cover has a couple of kind of hard to get to bolts at the firewall but 1/4" drive sockets and extensions did the job. The gaskets at the plug wells were really stiff from heat and oil, so it was a good thing to replace them and the cover gasket. I used Fel-Pro gaskets because they claim to be improved, and I have had good experience using their products.

11. Reverse the above steps to re-assemble.


Some extra notes:
1. It took me 13 hours to do the job, this being the first time I ever did this job on this engine. On jobs like this one I take lots of time to clean all the parts before re-assembly. That alone took several hours, using Gunk engine cleaner. The time included tool clean-up and put-away.
2. I used a torque wrench on all the bolts except for the alternator and A/C line because I wanted the joints to be right and I didn't want to be doing this job again.
3. Before I reconnected the electrical plugs I sprayed the terminals on each plug with CRC brand QD electrical cleaner.
4. I was worried about finding bolts that were seized in the aluminum head. I had none.

Tools:
1. Get a 1/4" drive torque wrench. It is hard to get to the valve cover and intake manifold bolts, that is if you can get to them when it's all assembled, to do any tightening.
2. Get an inspection mirror, 1-1/2" diameter works good.
3. Get a magnetic pick-up and 4 -prong claw pick-up tool for the bolts and wrenches that get dropped. The Trailblazer has a million holes and pockets where these fall into and I was glad that I could get the wrenches and bolts that got dropped into tight places without all the associated hassle.

Result:
The engine ran really good for a couple of days. Then the engine light lit. It turns out that the variable valve timing solenoid connector plug was still dirty. I cleaned the plug with CRC and that cured that. But in trying to understand how the vvts works, my research showed that it tends to have some filter screens that loosen and fall off. I didn't want that to happen to mine, since the path the oil takes is to the special timing gear on the exhaust camshaft. So I went ahead and got the solenoid from the local Chevy dealer. I thought I'd have to order it but to my surprise he had 3 of them in stock. It appears as though this is a common problem with the 4.2 engine. I specifically bought the GM part since I read stories where the part that was put on was an after-market part, like the Dorman brand, and found to be poorly constructed. I didn't want that hassle so I stuck with the GM part. Turns out that was a good decision because GM did a redesign of the solenoid by putting a retaining spring over the wire screen filters so that they can't fall off.

After all that, the engine runs good and the gas mileage seems to have gone up a little.

Glad it went well for ya. I've had mine a few months now an done quite a bit to it so its up to standards. When changing the plugs last weekend I found oil in a couple of the plug valley's too. It seems most aren't worried about it, but I have ocd when it comes to my vehicles. Tryin to sleep an just thinking about oil dripping on my plugs.....

Anyway I've got the book coming $7 duckies on ebay. I wrenched on way too many cars to let this go unchecked. Specially with under 65k. I'll probly get it done in a month or two when work slows. I'll start with a re-torque first an see if that does it.

Thanks for the details and good job:thumbsup:
 

Forum Statistics

Threads
23,234
Posts
637,113
Members
18,398
Latest member
DR.B

Members Online