intake gaskets? coolant leak, smoke test, codes, rough idle...

[alwaysFlOoReD]

I see youtubers doing that a lot so it must not cost THAT much... have any idea what it costs?

No, just where i work does it. I've never really done more than thought about it. But if it was a fairly high dollar vehicle, it makes sense.
I'll ask my boss what it costs and try to remember to post back.

 

[alwaysFlOoReD]

@Brain75
$30 Canadian for oil analysis.
My boss does lots of these so may get a discount.

 

[Shran]

I'd be suspecting a lower intake gasket leak. It could also explain your idle & lean condition. There are coolant passages at the front & back of the heads that flow through the lower intake.

It's pretty easy to mess up a lower intake gasket job on these engines. There are a variety of gaskets available, some are one piece that you bend to fit the spot it goes in and others that are two pieces and rely on a thick bead of silicone to seal. They both work OK...just easy to mess them up... and torque specs have to be followed precisely, and should be retorqued after a few heat cycles.

If you were just leaking coolant or just seeing a vacuum leak I would probably look elsewhere, but both at once, leads me to suggest looking there first. Kind of makes me think a previous owner tried replacing those seals and botched the job.

 

[rangerb4000]

I'd be suspecting a lower intake gasket leak. It could also explain your idle & lean condition. There are coolant passages at the front & back of the heads that flow through the lower intake.

It's pretty easy to mess up a lower intake gasket job on these engines. There are a variety of gaskets available, some are one piece that you bend to fit the spot it goes in and others that are two pieces and rely on a thick bead of silicone to seal. They both work OK...just easy to mess them up... and torque specs have to be followed precisely, and should be retorqued after a few heat cycles.

If you were just leaking coolant or just seeing a vacuum leak I would probably look elsewhere, but both at once, leads me to suggest looking there first. Kind of makes me think a previous owner tried replacing those seals and botched the job.

Thanks, basically have come back around to this conclusion also, based on the timeline of multiple symptoms. The oil just seems ancient and filthy, not watery. I may do a compression test this week.

I can only speculate so much about PO (old guy) but while it appears there was some work done to it, also some kinda random neglect, and towards the end he probably just did whatever to make it run. I traded a 3.0 for it that was also springing leaks left & right, so... not really complaining.

appreciate the feedback on doing the job. I have been researching a bit, definitely ran into the gasket configuration debate. while I would actually enjoy doing it just for experience sake/to see in there myself, I am leaning towards taking it somewhere, since it's winter and sadly I don't have a garage.

 

[rangerb4000]

So I did a quick (cold, dry) compression test this morning and found one cylinder low.
all read 150-155, except for the passenger rear, which read only ~95. I think that is #3?
That would also be the right location for the external coolant leak.
I was reading that low compression in one cylinder can point to valves, piston rings, cracked head... in this case with the coolant leak, would it be a head gasket blown to the outside/not mixing fluids?
edit: spark plugs appear normal

 

[Shran]

Interesting. This is what the block looks like on that side, there are coolant passages there, I suppose it's possible that the head gasket could be blown out there or a head crack in a weird spot.

 

[rangerb4000]

thanks for that photo!
judging from that, it seems plausible... I am still just getting familiar with this engine and possibly going in circles trying to figure out if it could be something else in disguise, or unrelated symptoms. those passages connect to the intake? would a blown head gasket have a slow but constant drip even when engine is off/cold/sitting for days?
edit: could a bad intake but good head gasket somehow cause low compression in one cylinder?

 

[Shran]

Yeah, they all run through the heads and cross over the intake through the front and back of the it - two ports per head, one on the front & one on the back.

There's a lot of coolant sitting above the block so yeah, it definitely could take several days to drip down that far if it's leaking externally from the head gasket. I would look to find any signs of the heads being off recently... do they look cleaner than the rest of the engine? There are a lot of possibilities here, could even be a head gasket that was damaged during installation or loose/broken head bolts. When other people touch things and then sell them, it's really hard to know what's going on.

 

[gaz]

@rangerb4000

I had very similar overall symptom (it was however on a 2.9l) but primarily coolant running from the rear top of the engine. It turned out that my lower intake manifold gasket had become compromised.

Once removed, it was visible and plain to see.

 

[rangerb4000]

Well... I went back and retested the compression on that rear passenger cylinder after the truck sat overnight. This time cold + dry it read 145, then I added a tbsp of oil to the spark plug hole, and the psi was identical at 145. I didn't retest the others, but yesterday they were all above 150 (and this one was way lower).
I'm assuming the identical readings are a good sign but not sure what to make of the differing result from yesterday -- I'm guessing it's imprecise to test just one cylinder and I should still redo the whole thing for comparison?
it's also entirely possible that I did something wrong the first time around and got a bad result... or did cranking yesterday move just enough oil that a wet test today wouldn't show anything?
Please excuse the learning curve and thanks in advance for any clarification.

 

[Brain75]

Just to double check since it's so easy to do when you have all the plugs out to begin with... .you are doing a plugs out compression test, right? - all the plugs are out so there is no restrictions (compression) in any other cylinders.

It will also expose a cross leak between cylinders (very rare) which is why it is preached as the right way to do a compression test.
If you went to the trouble of pulling all the plugs out, no reason not to spin it 5 more times and write down the numbers... trivial at that point.

Anyhow, I re-skimmed and I am with Shran on this one, post #18 - intake gasket. I think your low compression on the first test was either just OE (operator error) or gauge not perfectly sealed (the back ones are the hardest to get straight), flakey gauge, etc - not anything to worry about... my money is on the intake gasket.

If you aren't confident in your compression test or did it plugs in and just want to repeat, sure knock yourself out, but I don't expect it to be there.

 

[rangerb4000]

Just to double check since it's so easy to do when you have all the plugs out to begin with... .you are doing a plugs out compression test, right? - all the plugs are out so there is no restrictions (compression) in any other cylinders.

It will also expose a cross leak between cylinders (very rare) which is why it is preached as the right way to do a compression test.
If you went to the trouble of pulling all the plugs out, no reason not to spin it 5 more times and write down the numbers... trivial at that point.

Anyhow, I re-skimmed and I am with Shran on this one, post #18 - intake gasket. I think your low compression on the first test was either just OE (operator error) or gauge not perfectly sealed (the back ones are the hardest to get straight), flakey gauge, etc - not anything to worry about... my money is on the intake gasket.

If you aren't confident in your compression test or did it plugs in and just want to repeat, sure knock yourself out, but I don't expect it to be there.

thanks for the feedback - I agree, OE is likely with the compression test.
From reading about it beforehand, my takeaway was that it mattered less whether plugs were in/out and more that each cylinder was tested consistently... in this case, not being familiar with accessing everything and less than ideal weather etc to do this in the driveway, I decided to pull one plug at a time. Now I realize that all plugs out would have been more informative.

 

[rangerb4000]

I think it might be time to just take it apart and see what's what. I may be able to work with a local mobile mechanic rather than taking it somewhere.

I believe the truck is right on the line of being worth putting some work into... I enjoyed the week that we had together before all of this...

Thanks for all the help + input so far!
Will update.

 

[Brain75]

I wouldn't worry about a mobile mechanic, watch a couple of youtube videos, swing by oreillys/zone/advanced and get a gasket kit do it in an afternoon... helps soo much to have how to videos now a days...

https://www.youtube.com/results?search_query=ford+4.0+how+to+replace+intake+gasket

 

[Brain75]

I will throw out that if you get it apart and you aren't sure if the gasket was bad / the cause of the issues, take lots of pix and come back here - lots of guys here at all hours of the night - I keep the alaskans up at 3a.

As far as plugs out being the right way and guys online screaming 'you did it wrong', a crack between a cylinder wall and a coolant passage is rare, a crack between 2 cylinders is really rare and that is about the only thing a plugs out vs plugs in will find.... but it does make it go faster, spin easier, give you better looking numbers, and drains the battery less. The most likely crack is usually between 2 valves in a head or valve and coolant passage in a head.... at least in these motors. Once you bore it out a ton or we start talking about old sleeved engines (tractors and 1940's stuff).. or engines that sat for 30 years and had rain get in / trees start growing through em etc.