Yet Another thread on Lower Intake

[happydog500]

With all the threads on the Intake Manifold problems with the 3.8, I have one I can't remember if it's been commented on before.

I think the problem with the Lower is the gaskets they used where bad. Once you fix it, or update the gaskets, it should be OK. Over the years, I've heard people who change out the gaskets, but after it's fixed, it leaks again.

This is what I had happen to me (wondering if he really did change it is another possibility). Right after I fixed it, it was using antifreeze. I was thinking there might be a air pocket that made it so I had to add. The use happened for a while but stopped, then started again.

Why does it still leak after it's been fixed?

I found gooky stuff leaked and found it to be antifreeze leaking. Here is a picture of what it looked like from above and taking a picture holding the camera underneath the pipe. I wanted to find where it was leaking from but can't tell from this picture.

Any ideas or thoughts?

Thank you,
Chris.

P.S. after seven months, I may have enough to get the transmission fixed next week but am bummed out that after I finally have enough money, I may need more to fix this problem right after I finally get it running.

[Tech II]

To me, it looks like the throttle body gasket is leaking...was that replaced when the job was done?

[snshddog]

If I remember right that one has a plastic upper pleanum and they usually need replaced because they distort. There are 2 coolant passages in it.

[Jrs3800]

I agree with Tech... Was the upper intake replaced with a new gasket?

as well there is another coolant passage in the lower intake right under the throttle body... I have seen this gasket go bad and fail..

[enslow]

Agree with all the above. Also, sometimes the coolant passages in the UIM actually collapse.

In your picture, I see a little tan coloured goop above the LIM to block gasket, and a collection of gunk just below the LIM, but no trail on the LIM between the two sources.

1) What did you use for gaskets for the UIM? If that tan coloured stuff is in your coolant, you need to really flush the coolant system thoroughly. I can't think of anything that should be tan coloured at the UIM, TB, or coolant crossover gaskets.

2) What did you use on the ends of the valley gaskets? I think I see a dab of black RTV at the ends. I put about an inch of RTV from the ends of the valley gaskets.

3) How did you clean the gasket surfaces? Were there any scores on the aluminum gasket surfaces? On mine, there was a deep score on the iron surface, enough for my fingernail to stick in. I used a little JBweld to fill the score.

This is probably the reason I took a week to do my UIM/LIM gaskets. I knew I wouldn't want to do it again, so I spent about 2 days just cleaning gasket surfaces with solvent and non-abrasive materials. I used thread chasers to clean all bolt threads, and used a Q-tip with solvent to clean the bolt holes. I replaced the UIM with the Surefix from APN, replaced all gaskets, even the coolant crossover one. The only thing I did that I'm not happy with is I used a cheap Help! coolant elbow. Some have had those leak within a year whereas the OEM ones usually last much longer.

So far after 7 months it hasn't lost a drop of coolant However, I took much more care that most would, almost unreasonably so. I wouldn't cut it in a shop because I'd take way too long, but I don't know what short cuts I can safely take.

[happydog500]

We used FelPro Gaskets with the new APN Plenum sure fix. I got the updated smaller stove pipe with it. I did the job on my motor with excellent results. I lost the motor so I got a new one. The very good mechanic who replaced my motor put all new gaskets, and the new plenum on.

I was afraid it was the LIM. Maybe I only have to replace the upper? From what I remember, the orange upper gasket was a concern when I visited the shop. It didn't lay flat. I remember him commenting he didn't like that. "I'd feel better if this laid flat." I figured it will be bolted on and pushed down so it didn't matter.

Man, this would be great not having to do the Lower again. We put new fluid in when we did the motor swap, so it should be newer antifreeze.

Any way to know for sure if I take the upper off if I need to do anything to the lower? What should I look for? I'd hate to to the upper and find it's the lower again.

Thank you
Chris.

[Jrs3800]

Chris.. There is a coolant passage there, it has a cover with 2 8mm bolts iirc... There is a gasket there and sometimes if not replaced it can leak... This looks to be your case and the lower does not have to be removed to fix this... This could also be a throttle body issue.... But its hard to say without looking at it...

[happydog500]

OK, thanks! What would be the, "throttle body issue?"
Chris.

[enslow]

If you can, put a coolant pressure tester on and pressurize to 15 psi and wait. Using a light, and perhaps a mirror, see if you can find where the coolant is seeping from. If you used the APN UIM, the throttle body gasket it comes with is good, so I doubt you have the throttle body issue unless you didn't torque the TB studs properly.

[enslow]

The throttle body issues I'm aware of are warping of the UIM at the throttle body due to overtorquing. The other issue I've seen is the collapsing of the coolant passages in the UIM at the throttle body, possibly due to dexcool.

[happydog500]

If I remember, it leaked but not all the time. That's one thing I couldn't understand that it leaked inconsistently.

After this happened, my trans went out and it sat. I've had it back for a week or two and it hasn't leaked at all. Maybe after awhile it will lose fluid. It will go awhile and not lose any.

Does that tell anything by it not leaking all the time?

Chris.

[HotZ28]

Originally Posted by happydog500

If I remember, it leaked but not all the time. That's one thing I couldn't understand that it leaked inconsistently.

After this happened, my trans went out and it sat. I've had it back for a week or two and it hasn't leaked at all. Maybe after awhile it will lose fluid. It will go awhile and not lose any.

Does that tell anything by it not leaking all the time?

Chris.

The leaks can become more prevalent with lower ambient temps due to expansion/contraction of the plastic & gaskets. What ambient temp it was it when you first notice the leaks?

[happydog500]

During the spring or early summer it leaked and didn't leak. Now that I have it running again it's below freezing. It is not leaking but if I run it for a while it probably will leak again because it has leaked and not leaked.

Chris.