Help w/ 2001 F150XL, 4.2/V6 Oil Leak: Intake Manifold Gasket Replacement
 

Bought the truck this year (Jan. 2018) and had no oil leak whatsoever. About 2 weeks ago, suddenly a significant amount of oil started leaking. Did NOT start out slow; it went from "zero" to "significant" almost overnight. Took the truck to two different shops; 1st one put the truck on the lift, looked underneath, said oil was leaking from both sides of the engine and said it was probably both Head Gaskets. 2nd shop looked a little harder and said more than likely it's the Intake Manifold Gasket, but both Head Gaskets could still be bad. 2nd shop also said most of the oil was on the backside of the engine, so that would explain why there was oil on both sides. Wouldn't know until they did a "Seek and Repair" type operation. Estimate for Intake Manifold was $600, and $1,800 for both Head Gaskets.

I've decided to do the repair myself, and also decided to do the Intake Manifold Gasket first, to see if that's the problem, and to see if it fixes the problem. Seems unlikely to me that both Head Gaskets would blow at the same time with no overheating/low coolant at all. Have not yet done the test to see if there is exhaust gasses in the coolant, but I doubt there will be. This test was performed in January when I bought the truck and there was none at that time.

I know some things about vehicle/engine repair. I replaced the Head and Gasket on a 4 cylinder Mitsubishi truck about 20 years ago, and that went OK. I think the Intake Manifold Gasket Replacement is going to be less involved than that.

My main question at this point is, I'd like someone to explain to me and confirm that a bad Intake Manifold Gasket (lower) is sealing the engine oil somehow. Not sure why there would be oil circulating around or near the Intake Manifold. I don't want to put a lot of time, energy and money into a repair for a problem that CAN'T be caused for the reasons I think it is.

Second, the cost of the IM "upper" gaskets is about $40, and I'd like to know if that is worth doing.

When doing the repair, should I pull the whole IM off (all 3 levels, upper, spacer and lower) and then disassemble (or not), or should I take it apart one level at a time. I watched a Youtube video a few days ago where the Mechanic was doing the IM gasket replacement on a 5.4 V8 engine, and he pulled the whole thing out at once. Seems to me that, if the upper gaskets are necessary, it would be easier to take the IM apart in stages (vs. pulling the whole thing out at once and then disassembling it off the truck).

Also any advice from someone that has actually done this, or a similar repair.

Finally I'm looking at this part right here:

https://www.oreillyauto.com/detail/b...d+gasket&pos=4

I recognize the name "Fel-Pro" and I'm pretty sure it means high-quality, but want to make certain of this.

So you're not going back to shop 2 ever, right?

Thanks for the Reply. I really DON'T want to replace the rear main seal. The 2nd mechanic I talked to was pretty certain it wasn't the rear main seal because the engine was wet with oil higher-up than that. But no guarantees. Good to know head gaskets aren't prone to blow on a 4.2.

Assume that comment was aimed at "Adam" and that you meant to say "...back to shop 4 ever...".