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Removing the exhaust manifold from a Ford E250 van, 4.9L straight 6

I finally decided to replace a leaky manifold as the low compression and leaking oil has gotten to be too much. Not sure but it looks like I’ll have to remove the intake manni to get to it. A fortunate side effect is that the oil leaking from the manni seems to have lubricated most of what would be rust-welded bolts. I’d driven it like this since I bought it 3 yrs ago (don’t judge me. lol).

Anyone have any experience on this engine? Any tips would be appreciated. I have everything soaking in PB Blast now.

A leaking exhaust manifold won’t cause low compression or an oil leak.

A leaking exhaust manifold will cause the exhaust to be louder, and probably fill the passenger cabin of the van with exhaust gasses.


What year is your van?

There is no oil in a manifold, either intake or exhaust.

There is nothing about a manifold, either intake or exhaust, that will have an effect on compression.

What exactly are you trying to fix?

It’s a '94 and oil is leaking out just above where the manifold meets the head. It’s hard to see up in there so I assumed it was manni related. Exhaust IS entering the cabin asemaster.

Tester are you sure? I was told before (on this site if I’m not mistaken) that manni leaks causes sputtering and compression/power loss.

If you remove the exhaust manifold it makes more power.

Less back pressure/exhaust restriction, more power.

I think you have a valve cover gasket leak.


Do you have exhaust entering the cabin or do you have fumes from oil burning on the hot exhaust manifold entering the cabin?

An oil leak from a valve cover gasket sounds more like what you are describing in your original post. However, on that design of your engine you’ll need to pull off at least part of the intake manifold if I remember correctly.

However, neither a leaky valve cover nor an exhaust manifold leak will cause low compression or poor power. I think you may have more than one problem. But with a 20 year old van anything is possible.

I read that a manni leaks warp exhaust valves and cause compression loss. Like I said It’s been 3 years like this. Could that be why it’s now sputtering?

If there’s an exhaust manifold leak where cold air gets sucked into the engine it can crack/break an exhaust valve. And when that happens you’ll know it.


If you have an exhaust leak fix it, it’s unsafe regardless of what it does to power. But find out exactly where the leak is. It could be the gasket between the manifold and the head, a cracked manifold, the gasket between the manifold and the exhaust pipe (the ‘donut’), or a leak in the exhaust pipe. Only remove the manifold if you really have to, it’s a pain.

And I agree, sounds like you also have a valve cover gasket leak. Should be an easy fix.

Have you checked the compression?

Maybe I underrepresented my “power loss”. It has trouble going up steep hills now.

Asemaster I think it’s a combo of both burning oil and exhaust and yes I knew about the oil (it’s not bad, about a quarter size drop on my driveway overnight) and couldn’t miss the manni leak (it’s at the base part not along a pipe btw). I’m just wondering if it has morphed into a 3rd problem that replacing the manni won’t fix.

The problem might be caused from a restricted catalytic converter.

Your van is OBDI. And OBDI doesn’t monitor catalyst efficiency.


“And OBD1 doesn’t monitor catalyst effieiency.”

Not 100% true in all cases

My 1995 OBD1 Corolla 1.8 with 49 state emissions had a downstream oxygen sensor. Its only purpose was to monitor the catalytic converter

For those of you wondering . . . it was not one of those “sort of OBD2” 1994 or 1995 cars with the 16pin DLC. It definitely didn’t have one of those. And the underhood sticker did not say OBD2 compliant.

But generally speaking . . . no, OBD1 doesn’t monitor the cat

Sorry db4690.

But a 1994 Ford van doesn’t have an O2 sensor after the cat.


A restricted catalytic converter? you mean clogged from debris or something??? how would I check for that?

“If there’s an exhaust manifold leak where cold air gets sucked into the engine it can crack/break an exhaust valve. And when that happens you’ll know it.”

Will it rattle or start tapping? how will I know it?


No reason to be sorry

You just told me something I didn’t know

The engine will have a major misfire.


Your lack of power going up hill may be caused by a catalyst. A weak fuel pump. A worn distributor cap or bad spark plug wire. Restricted fuel injectors. A bad MAF or MAP sensor. Or any number of other things. I think it would be best to have the problem diagnosed by a reputable professional and then repairing it yourself if you can.

The lack of power is almost certainly not caused by the oil leak or the exhaust leak.

OK. Thanks guys. Since I plan on keeping the van and replaced the fuel pump a week ago, I’ll start with a long overdue tune up (plugs, wires, cap and rotors and fuel filter (they were out and had to order it)) and see where it goes. I’ll keep you updated.

@TEEJAY2, a thorough diagnostics using tools like a vacuum gauge, fuel pressure tester, compression gauge, and timing light can shed some light on what is going on. A restricted exhaust can be determined with a vacuum gauge if you know how to read it.