Leaky Intake Manifold Gasket?

[sweetbeats]

Hi all. Really hoping to get some input.

‘03 Eddie Bauer with the 4.6L V8 here. I was having a pretty significant coolant leak even under normal operating conditions and I tracked it down, pretty quickly, to the thermostat housing. I put in a new thermostat seal…the old one was pretty toasted…figured I had things licked but now it looks like maybe there’s seeping between the intake manifold and the head? I’m not sure…or maybe it’s just coolant that had leeched in there and it’s percolating out? See the pic below…the picture is showing the area directly below the thermostat housing and you can see it looks wet between the aluminum crossover pipe and what I think is the manifold gasket. Anybody else experience this? Do I just leave it alone until it seems more like for sure a leak? My problem is this is our daily driver, and I know me if I pull the intake manifold it’s injector seals, plugs, vacuum line inspection, throttle body cleaning…

 

[J_C]

I'd hook up a scan tool capable of live data. If your intake manifold has a leak, you will have high long term fuel trims, if not leaking bad enough to make it run poorly too. If it is running poorly you can spray something where the leak is suspected, or blow smoke at it, or use propane/etc to see if the idle changes.

If it is running okay, and you don't have a chance to hook a scan tool up, I'd keep an eye on the coolant level and especially that the oil looks good, no evidence of it starting to take a chocolate milkshake color. I'd idle it a while and check that before driving it anywhere as well as later on. While idling it, I'd carefully watch the tail pipe in case there's evidence of it burning out the exhaust and shut the engine off if there is. This may not apply to your engine but on some, coolant goes up through the gasket for throttle body deicing.

I'm not familiar with the valleys and crevices on that engine and can't make out much from your picture, but yes it is possible that some coolant pooled somewhere and as the engine heats up, it boils off.

Of course there are other things that can be done like pressure testing the cooling system, taking spark plugs out to see if any look wet, putting UV dye in the coolant (directly in radiator), running it and looking at it with a UV light.

 

[sweetbeats]

I'd hook up a scan tool capable of live data. If your intake manifold has a leak, you will have high long term fuel trims, if not leaking bad enough to make it run poorly too. If it is running poorly you can spray something where the leak is suspected, or blow smoke at it, or use propane/etc to see if the idle changes.

If it is running okay, and you don't have a chance to hook a scan tool up, I'd keep an eye on the coolant level and especially that the oil looks good, no evidence of it starting to take a chocolate milkshake color. I'd idle it a while and check that before driving it anywhere as well as later on. While idling it, I'd carefully watch the tail pipe in case there's evidence of it burning out the exhaust and shut the engine off if there is. This may not apply to your engine but on some, coolant goes up through the gasket for throttle body deicing.

I'm not familiar with the valleys and crevices on that engine and can't make out much from your picture, but yes it is possible that some coolant pooled somewhere and as the engine heats up, it boils off.

Of course there are other things that can be done like pressure testing the cooling system, taking spark plugs out to see if any look wet, putting UV dye in the coolant (directly in radiator), running it and looking at it with a UV light.

Hi. Thanks for the feedback. The motor runs like a champ, and no evidence of anything wrong at the tailpipe. To be clear we are talking about the intake manifold gasket, not the head gasket. There are no oil galleys that pass into the intake manifold. There *are* coolant passageways because of the crossover pipe to carry coolant from one cylinder bank to the other, as well as to the heater core. But an intake manifold gasket failure on this engine could not lead to coolant contamination of the engine oil.

I’ll just keep my eyes on it I guess.

 

[sweetbeats]

So it’s continuing to seep pretty significantly between the intake manifold and the gasket, so I’m prepping to pull the intake manifold. I’m going to replace all the lower and upper gaskets, and figure I’ll do the injector seals while I’m in there…check spark plugs and replace if indicated. Can anybody think of anything else I should do while I’m in there? I’m talking about stuff that requires parts…I’m putting a parts order together. There’s lots of other PM tasks I’m going to do…clean the throttle body, MAF sensor, etc. but if anybody can think of other stuff I should do that requires parts let me know. Again, truck runs like a champ, but I’m confident the manifold gasket has failed.

 

[sweetbeats]

So here’s the deal…there are gaskets between the aluminum crossover pipe and the plastic intake manifold casting. The gasket on the driver’s side on my Explorer had failed…eroded toward the rear:

So if you have coolant leaking from below the thermostat housing OR at the other end of the crossover pipe, it might not be the intake manifold gasket, but rather the gaskets between the crossover pipe and the manifold.

I had trouble finding these gaskets. I found ones that *looked* correct, but were listed as not compatible with my ‘03 V8 equipped Explorer…Crown Vic yes, F150 yes…my local auto parts store worked with me and ordered the set and had me not pay for them so when they came in we could compare to the old gaskets and if it was a match I’d pay and take them home, and if they didn’t match they’d let them go back to the warehouse. Anyway, I got them, they are a perfect match; Mahle part number GS33745.

Here’s some additional random pics of the disassembled intake manifold so you can see where the gaskets live:

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