A Grand Marquis far from home - Life with my 1988 Mercury Grand Marquis GS

[Tynnerstroem]

You're not wrong sly DerekTheGreat . The plan was to have the Thunderbird available for situations like this but with it being hit and scrapped I'm now without a spare car. Since it was scrapped I've been keeping my eyes on the market but nothing suitable has popped up, so it's all essentially a perfect storm.

When it comes to the freeze plugs, should that be the case then I assume I would do both plugs (both heads), since if one is shit then the other can't be far behind. How hard is it getting the heads off of these motors? Can it be done in a driveway of a fairly well-equipped garage?

Also, you mentioned freeze plugs between engine and trans DerekTheGreat , how do we know if it's those? Reasonably if they are located between motor and trans then that coolant shouldn't be getting out?

[DerekTheGreat]

I haven't had that headache yet. If I did, I'd start by cleaning around where the trans and engine mate up as well as the cylinder head and rear areas of the lower intake. Get some light in there, run the engine and observe for leaks. Hopefully, it's not that.

[sly]

the ones between the engine and trans will be leaking out of the observation panel at the base of the trans like a rear main seal leak would and wouldn't be on the top of the trans or the firewall.

[Tynnerstroem]

This is where the leak seems to be coming from, that’s the panel you were talking about right sly?

[Arquemann]

That's coolant, there are no coolant plugs in the back of a 302 block. It has to come from above.

[Tynnerstroem]

That's coolant, there are no coolant plugs in the back of a 302 block. It has to come from above.

Oh I thought that what was everyone was talking about earlier, coolant plugs between the engine and transmission and that those would be leaking. It would’ve seemed reasonable because I can’t for the life of me find any leak above, either from coolant plugs in the heads or the intake. But maybe I’m confusing things.

[Arquemann]

Oh I thought that what was everyone was talking about earlier, coolant plugs between the engine and transmission and that those would be leaking. It would’ve seemed reasonable because I can’t for the life of me find any leak above, either from coolant plugs in the heads or the intake. But maybe I’m confusing things.

That's what I'm a bit confused about too. Surely all the GMN veterans would've known that. The coolant has to be coming from the heads, intake or some coolant line.

[sly]

I've never been in far enough to take a transmission out much less a flex plate off. If there are casting plugs on the back of the block, they would be behind the flex plate.

Searching images of 302 blocks shows only a cam port plug and that's it. No rear freeze plugs in the block. Rear casting plugs are heads only. So drips of coolant there should only be from the heads or above. If there is a coolant leak between the transmission and engine block, that means the block is cracked. So I would wager all of the previously mentioned locations to check involving hoses, intake, and heads.

[kishy]

Speaking simply in probability here, it's unlikely to not be the gasket(s). That's like, old SBF 101: the intake gaskets leak.

If there were a "I just bought this thing and I don't know anything about it, how do I cut down the list of potential things that will go wrong with it within the first 365 days of ownership" checklist, I'd be putting intake gaskets as the absolute first item on the list.

Well, maybe TV bushing, but the spirit of my point stands.

[Tynnerstroem]

All right, that’s interesting. I’ve swapped all of the hoses including the ones to the EGR, so I feel confident that it’s not one of them.

There is this wheezing, whistling sound when I turn the car off, as if the pressure inside the engine seeps out when the car is turned off. That has led me to believe that there’s some sort of hole somewhere, and it sounds like it’s at the back of the motor, back of the passenger side to be specific, which would point towards it being a freeze plug in the head. But what throws me is that I can’t really see a leak there, although I don’t really see anything all that clearly back there.

Intake gasket leak would surely be reasonable, for all I know it’s the original gasket on there. But tell me this though - since I see the coolant coming from that hole that you see in the image, doesn’t that mean that it’s coming from between engine and trans (and as such that the block is toast)? Or can it seep from the intake or a head and make its way down that way? Because I would assume that if it comes from up top it would come down the side of the transmission, and not ”through” it or whatever.

[Arquemann]

The AC pressures equalizing makes quite a bit of noise.

Coolant from above can seep between the engine and trans, but in those quantities it ought to also be running by the side of the trans.
You need to get your hands behind there and feel all around the head core plugs, the seams between the heads, block and intake. Or borrow a boroscope. There's plenty of room between the engine and firewall, the EFI intake just makes things a bit harder to access.

Cracking a block in the summertime is highly unlikely.

[WagonMan]

Can you borrow or rent a radiator pressure tester? Leaks can be hard to find with moving parts, wind from the fan etc. Wipe everything down and pump up the system with the engine off. Look and listen for the leak. WagonMan

[DerekTheGreat]

I was wrong. Thought there were freeze plugs at the back of the block behind the flex plate, but there's not. Whew.

[Tynnerstroem]

Thanks for the following up gentlemen. I'm going to take a deep breath, borrow one of those borescopes and look again. It would be the hugest of reliefs if I only had to remove the heads or manifold, and not the entire motor.

[Tynnerstroem]

I ordered a borescope from Amazon, which for $30 got me a long ass wire, color screen with zoom and a lamp as well. A fine purchase indeed!

So looking at both of the freeze plugs on the back of the block, it looks like this:


To me, this looks moist and maybe a bit oily, but certainly not like it's actively dripping coolant out of them. The valve cover gaskets I replaced earlier and they were shot and the valve covers had lots of oil around them, so the oil being there seems reasonable to me. Even with the car running, none of the freeze plugs actively seemed to have coolant dripping out of them, even as coolant was dripping to the ground. I do as such rule these out to be the source of the leak. The EGR-cooler lines are nice and dry, as are the hoses going to and from the heater core.

This is where I'd want your input - that basically means it's the intake manifold gasket right? Of course, the block could be cracked somewhere, but I'm not counting on that. I've been running the car in freezing temperatures during the winter but only with properly mixed coolant, never with water only. I'm leaning towards tearing off the intake but would love your input before I do.

1. Is it reasonable to assume that the intake gasket is the culprit?
2. If I do the intake gasket, what other things should I be doing at the same time? I removed the plenum this spring so the plenum gasket, coolant hoses to the EGR and associated vacuum lines are done already.