Cracked intake manifold? [Archive] - Forum


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05-29-2011, 10:36 AM
Has anyone here cracked the cooling jacket on the lower intake manifold before? I was having an overheating problem and noticed coolant under the thermostat sitting next to the rtv where the LIM and the block meet. After tearing it down, I noticed what look like water stains on the LIM on the side of the water jacket. I'm wondering if there is a way to pressure test the water jacket. I have dye penetrant on the way, but I'm not sure how well that is going to work on the rough surfaces involved.

If it is cracked, anyone have an idea how much it is for a replacement? Trying to do this on the cheap...

05-29-2011, 11:39 AM
It's more likely a failed LIM gasket and coolant is leaking out between the head and the LIM.

05-29-2011, 12:25 PM
It's more likely a failed LIM gasket and coolant is leaking out between the head and the LIM.


05-29-2011, 01:58 PM
I have a stock LIM if you end up needing one

will sell cheap too.

05-29-2011, 05:01 PM
I had already changed out the LIM 18 months ago(great walkthrough by the way), and when I put it in I put a thin coating of black hi temp rtv on both sides of the LIM gasket, both the intake valve and water jacket. It sounded like a good idea at the time, but I'm wondering if I shouldn't have, especially on the water jacket.

Photo of area in question, last time I replaced the gaskets I cleaned every surface on the LIM and heads, only reason I'm worried I cracked the LIM. I couldn't get a decent picture of the top of the cooling jacket, the camera wouldn't focus at that short of a distance...

On another note, I did find that my fans aren't running when they're supposed to(or at all, not sure about that). I'm pretty sure that's what did it in, after I did the gaskets last time(all the way to the head gaskets, last time I was getting coolant in the oil...) I was only driving 18 miles each way to work, all highway. But when I drove it down to my dad's in north FL it boiled over when I stopped for gas and cigarettes. This was after about 2 1/2 hours of driving at 1 am, outside air temp around 60F or so. I checked the oil, nothing there. After reading the boards on here, someone mentioned a bad waterpump can cause a backsurge like that.

05-29-2011, 09:25 PM
Yeah, you don't need to and shouldn't put RTV on the entire LIM gaskets. It only needs a little on each corner of the gaskets and across the bridge between the heads. I doubt that would cause a leak though. The most important thing is making sure the bolts are tightened properly and that the right threadlock is used. That is what most people screw up.

Anyway, cracking a LIM would be very rare. You'd have to way over tighten a bolt to do that and it's more likely you'd strip the thread or break the bolt before that would happen. The LIM is usually very strong. From the sound of it, you may have overheated it before, so it's more likely that either the LIM or the heads could have been warped which would cause them not to seal properly and leak. It also possible it could be leaking from where the heater coolant pipe goes into the thermostat housing and dripping down the LIM to the block from there. Might need to replace the O-ring on it, and make sure the nut on the retaining bracket is tight.

05-29-2011, 10:28 PM
I didn't think about it leaking at the heater pipe junction, I'll look into that in the morning. I didn't replace the o-ring on it last time I'm pretty sure.