I5 Intake Manifold Replacement Questions

[cbetts]

I think my intake manifold is cracked. I have been troubleshooting a loss of power issue the last few days and have been going thought the usual culprits:

• Dirty throttle body
• Bad spark plugs
• Dirty air filter
• bad fuel
• Dirty MAF sensor

Now that I have gone though all of that, I have been focusing on other things. I noticed a vacuum hissing noise and tried to focus in on it. as I was leaning over the driver's side fender, I tugged a little on the throttle body and heard the hissing get louder along with the engine running rougher. I pushed on it and the hissing stopped.

So, how hard is it to swap the intake myself? It looked pretty straight forward in the shop manual until I got to the A/C compressor and alternator removal. I do not have the tools to do the A/C portion. Is it possible to remove the intake while leaving the A/C and alternator in place? I just got done spending $3400 having both differentials rebuilt so I am not ready send it down to Anthony in Santa Ana just yet.

Any advice is appreciated. Thanks in advance.

 

[H3slate]

I think my intake manifold is cracked. I have been troubleshooting a loss of power issue the last few days and have been going thought the usual culprits:

• Dirty throttle body
• Bad spark plugs
• Dirty air filter
• bad fuel
• Dirty MAF sensor

Now that I have gone though all of that, I have been focusing on other things. I noticed a vacuum hissing noise and tried to focus in on it. as I was leaning over the driver's side fender, I tugged a little on the throttle body and heard the hissing get louder along with the engine running rougher. I pushed on it and the hissing stopped.

So, how hard is it to swap the intake myself? It looked pretty straight forward in the shop manual until I got to the A/C compressor and alternator removal. I do not have the tools to do the A/C portion. Is it possible to remove the intake while leaving the A/C and alternator in place? I just got done spending $3400 having both differentials rebuilt so I am not ready send it down to Anthony in Santa Ana just yet.

Any advice is appreciated. Thanks in advance.

It has been awhile since I had to mess with the intake manifold, but yes it can be done without removing the A/C portion. I would have to look at my rig to see how I did it.

I had a loss of power issue that was sporadic, I went through the same troubleshooting until I discovered that my intake manifold was loose. The bolts had backed out somehow, I had never touched the manifold before this happened, and was loosing the seal to the engine. I would remove the throttle body or intake and check to see if the manifold is loose.

I was able to remove the intake manifold and replace the gaskets without too much issue. I do remember having to go through the drivers side wheel well for access to some of the bolts.

Hope this helps, good luck!

 

[4speedfunk]

Probably gasket shrinkage...a huge problem at GM for the past twenty years. For some reason they can't seem to fix it.
I used some special gaskets from Fel-Pro called "problem solvers" on my 5,7L Vortec motor. They were expensive but, they seem to have worked.

 

[CaseyS]

Check the pcv hose connector under the resonator box. That was a culprit on mine at one point.

My fix was rather drastic.

 

[cbetts]

Check the pcv hose connector under the resonator box. That was a culprit on mine at one point.

My fix was rather drastic.

PCV line has recently been replaced with an oil catch can. Based on the noise, there is clearly a problem with the intake whether it is cracked or loose.

Which direction does the engine torque? I am also thinking that the AirDoc may have helped crack the manifold if I have a broken motor mount.

Sent from my XT1254 using Tapatalk

 

[650Hawk]

I'm actually leaning towards the manifold being loose rather than cracked. It's a common, well known issue on the i5, AND if it was cracked but still bolted tight, pulling/pushing on the throttle body wouldn't change things; being loose would.

 

[cbetts]

Got the intake fixed today which took all day. I started off by putting removing the front left wheel and inner fender.

It was pretty straight forward with the exception of the alternator. I found a thread on HF that showed how to remove the alternator without removing the A/C compressor. I left the alternator dangling in the hole for now. Once the alternator was out of the way, I could reach the front bolt of the manifold. Just a tad loose . . .

There is a plate for mounting wire harnesses on the lower part of the manifold with three bolts holding them in. Pop this out. Also removed the dipstick tube. Make note of how it is routed. Took me a good half hour of dinking with it to get it back in place. Now the none bolts for the manifold can be reached.

Once the manifold was out, I could lift the alternator out. Sine it already has 100K miles, I went ahead and put in a new alternator. I thoroughly cleaned the intake and put in new gaskets. Reassembly went smooth, except for the stupid dipstick tube and dropping a bolt that took me another thirty minutes to find (rolled into the differential skid plate).

Truck has regained all the power! Taking it work tomorrow for a trial run. Thanks to everyone that gave me advice. As always, H4O has the best Hummer owners ever!

 

[4speedfunk]

Wow. Those are some crazy-looking ports. These motors scare me....hope I never have to touch mine (other than to replace it with something else).

 

[H3slate]

Glad you got it figured out. I forgot about the dip stick removal. It was not fun putting it back in.

 

[woodwardsh3]

Was that bolt all most ready to fall off in the 2ed picture?

 

[woodwardsh3]

OH i for got did you put blue loc tite on the bolts?

 

[cbetts]

Was that bolt all most ready to fall off in the 2ed picture?

Yep. Fortunately, the bolts have retainers to keep them on the manifold.

OH i for got did you put blue loc tite on the bolts?

Unfortunately, no. I thought about it after I was done. I am not pulling it apart again anytime soon though. I am noticing all the scars on my arms and hands for yesterday's efforts.

 

[4speedfunk]

Not sure how complicated it would be on an H3 but, in the past...I have found it easier to un-bolt and remove the entire dog-house (fenders-grille-hood) in one piece...and set it aside. This will give you full, walk-around access to pretty much do anything to the motor. I used to do this on my 79 Malibu. It was alot of work but, the access I gained was worth it.

 

[cbetts]

There is a lot attached to doghouse. I used to do the same, but times and cars used to be simpler.

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[Mr_Rich]

Not sure how complicated it would be on an H3 but, in the past...I have found it easier to un-bolt and remove the entire dog-house (fenders-grille-hood) in one piece...and set it aside. This will give you full, walk-around access to pretty much do anything to the motor. I used to do this on my 79 Malibu. It was alot of work but, the access I gained was worth it.

That's a good idea except for the problem that it looks to me that part of the H3 body is built more like a unibody than a 60's/ 70's car that you could remove the front clip fairly easily. The H3/ T is more like my '98 Firebird that has extremely limited access to the sides of the engine for simple maintenance like changing spark plugs. I understand Craig's remarks about scarred forearms very well.

 

[cbetts]

So, I am on day two and ol' Bessie drives like new! Drove up 190th Street in Torrance (scene of the infamous Halicki Mustang jump in the original Gone in Sixty Seconds) in fourth gear. For the last year, I thought my engine was just getting tired.

Now I just need my KMW UCP and I will be ready for some trails again!

 

[rascole]

So what was the issue? Crack or loose bolts?

 

[cbetts]

So what was the issue? Crack or loose bolts?

Loose bolts.
[video=youtube;YPmb5dlP9nA]https://www.youtube.com/watch?v=YPmb5dlP9nA[/video]

 

[JPaul]

That's crazy. I've never heard of an intake loosening up like that.

 

[4speedfunk]

Please tell me GM has cancelled this 5-cyl. nightmare. Some motors deserve to be extinct.

 

[Mr_Rich]

Please tell me GM has cancelled this 5-cyl. nightmare. Some motors deserve to be extinct.

I think we saw the last of the Atlas engines in 2012 except for the four banger that they're still using in the Gen2 Colorado & Canyon trucks. Just think; there was a rumor they were going to use the 3.7L as a standard engine in the full-size trucks. I wish Hummer would've survived a couple more years so that we could've gotten the 3.6L V-6 at least. It seems GM is committed to that engine.

 

[rascole]

Please tell me GM has cancelled this 5-cyl. nightmare. Some motors deserve to be extinct.

Ouch, so much hate. :gaah:

 

[cbetts]

Finally got to get up to highway speeds this morning. Now I am actually able to use fifth gear again! WOOHOO! :thumbs: