Head Gasket or Intake Manifold Gasket - How to tell?

[RayInStl]

Hey guys. I recently picked up a 2002 Explorer with the 4.0. It had been wrecked but otherwise ran and drove. I replaced the radiator, fan, fan clutch, and water pump (all damaged in the impact). While replacing the water pump, I removed the thermostat housing to give myself room. So I replaced the t-stat housing gasket at that time (I guess I should really call it an o-ring). After filling the reservoir with water to check for leaks, I started the engine to make sure the thermostat was functioning and the housing wasn't leaking.

I didn't find any leaks and things were looking promising. However, I decided to check the oil to make sure things were still looking good. My worst fear. Water in the oil. It wasn't bad at first but the longer the motor ran, the more watery the oil became and so I shut it down.

My first thought was that after the accident, the previous owner had run it with the damaged radiator and overheated it, causing a head gasket leak. But I also know that these 4.0's are prone to intake manifold gasket leaks that cause water to get into the oil as well. The engine purrs like a kitten. Not even so much as a miss. So my initial thought (hope) is the intake manifold gasket.

I don't see any leaks on the outside of the manifold, but I can't see it very well due to how the upper intake overlaps the valve cover. Is there any sort of test or something I can look for that would conclusively say "head gasket" or "intake manifold gasket"? I'm sure the intake has to come off to get at the heads, so I guess I could just start disassembly and see how the gasket looks, but I'd rather know ahead of time.

Thanks!

Ray

 

[mbrando1994]

I believe intake manifold gasket failure is linked to a hissing noise or suction noise as air will be leaking out of the inlet holes. My 03 only has one set of gaskets for the rings, some have an upper and lower set. I do not think this is in any way related to water getting in the oil.

It does sound like a head gasket issue but have someone perform a compression test on all cylinders. This will give you some evidence either way.

In order to get to the heads the manifold has to come off, In fact, the manifold usually has to come off just to get the valve covers off on these models. Your best bet is going to be pulling the engine. Not even sure if head gasket replacement can be done in vehicle. It probably can be, but it will make your life so much easier to remove it. The two rear most bolts on the intake manifold are even close to impossible to remove. I had to sit on top of mine hunched over, pressed against the hood using extensions, various ratchets, u-joints, adapters, you name it, they certainly didn't make it easy on us.

My best bet is it's a head gasket. Hopefully you don't have a cracked block or head, although if what you're saying is true, it may just be the gaskets. Replace both while engine is out, also have a look at crankshaft bearings and timing. Might as well tune those up while you have everything apart.

 

[p71]

The intake manifold "gasket" on the 4.0 is actually six oval shaped rubber gaskets which correspond to each individual cylinder. Unlike the 4.6 V8, coolant is not being routed through the intake manifold, so there is no way a 4.0 manifold gasket/intake manifold defect would allow water to mix with oil.

 

[RayInStl]

Thanks guys. We went ahead an pulled the intake and found out no water jackets run through, so looks like head gaskets. Oh joy. Are the transmission to engine bolts as impossible to get to as they are on the 98 explorers? We actually bought 2 explorers. The first was a 98 that we're pretty sure broke a timing chain. We got the engine 80% out but getting those top transmission bolts proved difficult. So we decided to try this 2002, since it still ran. We figured we'd just have to replace the front clip and cooling system. So much for that idea!

Either way, we want to continue with the 2002. At this point we're only about $1,200 into it. So even with head gaskets and the extra work, I think we're still in the green. But if those bolts are as hard to get to, I don't know if that's viable.

Thanks again for the help!
Ray

 

[RayInStl]

Anybody know how hard those tranny bolts are on this year of explorer? I poked around last weekend and things seem to be more accessible than they were on the 98. But things couldn't get much less accessible than on the 98. We were using two 24" extensions, a swivel and used a cell phone as a scope so we could see what we were doing. It was an exercise in frustration! Then, on top of that, to get at the starter, you had to remove the front driveshaft.

 

[Stick4503]

The best way to get to those bolts is from the top. Take the hood off. Take off as much of the plastic from the top of the engine and squeeze your hand an ratchet back there. You may have to snake a long extension and wable from the bottom to break it loose first. The recommended torque on those is fairly light so should not be too bad.

Headgasket replacement is not just a unbolt and replace. Your engine has several timing chains that need to be set back in time using a special tool set that will set you back $200 -$250. Search this site for timing chain replacement and you will find hundreds of post. It's not that bad but they did make it troublesome. If you go to the trouble to pull the engine I would change the chains and cassettes. About $300 from RockAuto.

 

[RayInStl]

AAAAAAH. I forgot about the damned timing chains. I wish I'd never set my eyes on one of these 4.0's. I'm sure the engineers has a good reason to do what they did, but my god, what a nightmare to work on.

Thanks for the heads up.