97-01 Intake Manifolds - Common Locations to Crack?

[markfothebeast]

SOHC V6 4.0L

I've read about speculation on cracking but can find no photos other than info stating "my mechanic told me so". I had to replace the lower thermostat housing and I've got the upper intake manifold off for the 3rd time in about 2 years and went over this turd with a fine tooth comb. Not that I'm having issues but just curiousity. I put it in the parts washer and cleaned her up.

I found one crack which was my fault because I put a different bolt in but it does not come near the air way, only in to the outer shell. It's basic ABS plastic so it's not a hard fix if even necessary. The bolt holes appear to be intentionally separated from each intake air way and I can't find anywhere that it would possibly cracked unless it was beat. I even overtorqued when I misread ft lbs for inch lbs when I had too many beers last time. I corrected it but I still see no cracks other than the bolt hole in the front corner.

 

[RandomNerd2000]

I've wondered the same thing, I've resold a couple though and make decent money off people, though I don't get how you would crack it unless you're an idiot.

 

[markfothebeast]

The torque rating for the bolts seems too light at 62 inch lbs. This is something like 5.1 ft lbs. Considering that the bolts are self tapping, you'll never get an accurate torque reading.

I'd still like someone to show where the upper manifold tends to crack or if shops are just out to rape the willing.

 

[markfothebeast]

I pulled the upper manifold off when it was 2 degrees fahrenheit and it still did not shatter or crack. I'd like to figure out if these cracking manifolds happen to be fact or fiction.

I've always been nervous about torqueing these plastic Ford parts on properly. But as i stated, I torqued the upper manifold to 62 ft lbs which is nearly 12x tighter than spec.

This is the last round for the Explorer. I'm going to JB Weld everything together next time.