3.8L Intake Manifold Gasket Replacement
 

I am getting ready to replace the lower intake gasket on my 2007 JKU. I have a small coolant leak near the front of the intake and I believe that I have the oil leak in the rear of the intake that migrates down the bellhousing.

I have read some "how to's" and even watched a video so I am feeling pretty confident about the deal as I have a fair amount of mechanical experience.

I do have a few questions so if anyone else has experience that could help, it would be much appreciated.

1. In the picture below on the upper right (1) is the intake, (2) are the plastic things that secure the wiring (3) is the rail and (4) the fuel line. What type of sensor or sending unit is (5)? I am familiar with the ECT sensor near the thermostat housing but I do not know what this is for?
2. Also are there any sending units/sensors on the rear of the intake that I should be aware of? In my research I did not find any. When people talk of the oil leak coming from the intake is it just leaking out of the valley?
3. In some of the step by step's I've seen online it states to pull the injectors and the fuel rail. I see no reason to do this unless there is a really good reason, do you agree?

I have the new gasket and I have rented the fuel line disconnect tool. Also, while I have the coolant drained I am going to replace the thermostat and that ECT sensor as well as the upper and lower radiator hoses. I think these last items are probably very unnecessary but in the spirit of going overboard I thought why not...and I am getting ready for a 3 + week over 5,000 mile journey across the county next year and I want everything to be in top shape.

Now I just have to decide if I am going to use the mopar coolant or go with the Zerex G05 stuff.

Anything I missed? Thanks for any input.




Attachment 672610

So I finished the intake manifold gasket job. It actually went pretty smooth. I did run into one problem though. I stripped out some bolts for the upper intake manifold. That aluminum in my lower manifold must be very soft. I was using a torque wrench, 1/4" drive, and they would not take more than about 80" pounds. I ended up tightening the other 5 that I didn't strip out to about 70" pounds and called it good. It seems to be fine and even though 3 don't tighten any longer I think they are still at about 50" pounds. I was using a stepped method of torquing the bolts 50-80-105" pounds when I discovered this issue. I will have to go back and fix this so they all torque to the right spec.

Also the gasket was definitely leaking some coolant. Most of it between the intake and the gasket on the drivers side. It took me quite a while to clean the corrosion off the lower intake.

It seems to be running good. No leaks initially, hopefully that holds true indefinitely.

Attachment 672762

Attachment 672763

Thanks!
 

Just started this task today and this thread is so helpful.
Right now i am having trouble getting that 13mm bolt on the very back passenger side out. Hard to get a socket on it squarely.
will try again tomorrow.

I did this long delayed job last year about this time, along with timing chain replacement. Jeep is an '09 JKUR that only had 65k on it and developed an upper oilpan leak. While the pan was off I discovered the loose chain. The lower intake gasket had been weeping in front above the water pump for years, so I decied to tackle the gasket at the same time as the timing chain job. From what I can remember:

1) The upper manifold with the throttle body came off easily, but the push tabs at the injectors, the conduit for the harness and the plug at the throttle body either crumbled or broke on reinstallation. I had to get a repair kit for the throttle body plug from Mopar that cost $50. I replaced the crumbled conduit with the stuff they use on the ignition wires, much moe durable, and just zip tied the injector plug lines to the tab mountings.
2) The lower manifold gasket has metal plates at each end. These can be loose and FALL INTO THE OIL PAN when you pull off the old gasket!!! Do yourself a big favor and pull these off before you try to yank off the old gasket. (Don't ask how I know this...just DON'T! ;-) )
3) Make sure you get the new style, which has raised ridges around all the ports. The old style flat gasket is still being sold by the aftermarket and will leak just like the original.
4) Clean the threads for the lower intake manifold bolts thoroughly and blow out & chase the threads in the heads. Use a bit of oil on the threads or a dab of anti-sieze and they'll torque up smoothly. Take the bolts up in three progressively tighter steps until they stay at torque spec.
5) The factory spec for the upper intake manifold bolts is bullshit, way too much, as is the spec for the thermostat housing. Use you head, snug them up firm and give them just a bit more. I came close to stripping one out but caught it in time.

Hope this helps.

How did you know this was an issue? Were you getting coolant in the oil?

It was a slow leak out the lower front of the manifold. Would gradually lose coolant. When I pulled the manifold I learned it was weeping out the back side as well.

Ahh, ok. Mine was very slightly low on coolant when I looked at it the other day, but I don't think it is a leak. I keep checking it and it seems fine. One of the several things I monitor as my 3.8 ages. Still runs like a champ, though.

The geniuses at Jeep designed the coolant reservoir with an overflow vent that can spew coolant on steep climbs and rough terrain. That may be where your coolant is escaping.

80lb-ft you crazy intake manifolds never require that much torque. It must have been in- lb not ft- lb .That's why you stripped the threads.
lo

Replacing the intake manifold gasket is one of the things we just completed. Also broke an oil pan bolt off and tried to run it to see if that ended up leaking (ofcourse it did) so I drained the oil and pulled the pan to have better access to extracting that bolt. When I drained the oil however, it was brownish milky coloration and looked like it had coolant/water in it. I had only run the engine for about 5 miles on that new oil. After reading your comments about the "old style" intake gasket, that's exactly what I put on mine. It didn't have the raised edges that I recall. I'm wondering now if coolant was able to get into the oil from that location now? If it leaked into another passage seems like it would get right into a cylinder.