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Please help. Northstar freeze plug.

97485 Views 389 Replies 26 Participants Last post by  Ranger
Hello guys. I have a 2001 Seville STS, a freeze plug (core plug, welch plug) fell out. The plug is (was) located on the rear of the left cylinder head, left front corner of the engine bay, behind the water pump housing. I can't upload pics because I'm posting this from my phone but even if i could it would be hard to see the hole, it is barely visible, it's somewhat blocked by the water pump belt as well as the housing (have to look very closely at a strange angle). I have already bought the new plug, but how do I access the hole to install? Does the entire housing have to be removed? If so, how involved is this going to be? I've already removed the air filter box/ducting, water pump belt shield and disconnected the hoses from the housing.

Any help would be greatly appreciated. Thank you.
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Dry means dry. The only place you would seal is the thread sealer on the port bolts.

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Hmm, so how the heck do you keep the new gaskets in place while reinstalling? Also what is the correct sealant for the port bolts?
Just a thought. Are the bolts a tight enough fit that I could leave them in the holes with enlugh thread protruding to hold the gaskets in place?
The bolts will hold them in place but there is no guarantee they won't fall off.

I used some masking tape on the edge but it held no better than the bolts shifting the part around to line it up. There is a risk of the masking tape getting into the gasket surface & sticking, you would then have to pull it out again to clear the gasket surfaces. One did fall out of alignment but i was able to get it back into place & start the bolts.

This is the kind of crap that makes this a difficult task. The use of masking tape not very ideal.
All 8 bolts are held in place by the gaskets in this pic.

You will notice the upper ports are different on the later model N* along with how the TB mounts.

The later model N* x-over looks like this.
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Thanks for the pics. What type of sealant is used for the bolts? Do they pass through the coolant passages? Looking at the pic it looks like a few do.
Some of the original sealant remains in the bolt threads, I just used a brush on pipe joint sealant sparsely applied.
There are many thread sealers out there to choose from, you only need a tiny amount.

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I've read so many threads on crossovers and water pumps in the past couple days I'm beginning to mix things up. I know there is an improved design water pump cover and seal, anybody know if there are also improved design crossover seals? I thought I read something about older ones being blue (as in johnnys pic) and newer ones black. Or is there only one design since I have the 2000+ crossover?
Ah - yes - good old rectum-seal - good stuff!
the crossover seals have changed colors over time for the 1999 and older... but are still the same design...
the 2000+ crossover seals haven't changed at all (that i know of)
and even though the lower ones look like they're the same between the -'99 and the '00+ they are different

the pump cover is very slightly changed in an update around the 2003 or 2004 years and it applies backwards to all years
you can tell the new design by the couple square ears around the edge

the original design would sometimes weep a bit of coolant for some reason... the gasket has changed also so that's probably part of it
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Thanks Rippy, I'll be ordering the seals (and silicone hose) tomorrow. I replaced my water pump just under a year ago, I used the new style seal and cover. I'm sure I'll have more questions when I do the job, I just hope it doesn't end with me asking for the number of a suicide helpline ;) I'll be taking pictures as I go to help with reassembly. Maybe I should post a tutorial. I can't find one on here.
The blue seals are OEM from Cadillac. Nothing special going on.

The blue or orange part of the seal isn't the problem, the black plastic laminate that the seal is supported by is what deteriorates. Once that breeches the silicone blows out. Other GM motors have the same problems only at the intake manifolds. Same gasket structure. This gasket design works excellent & is even reusable on the trans pan, front cover, But exposure with dexcool is slow death to the black plastic.

The Dexcool does impregnate the plastic over a long period of time, not long enough. The gaskets I changed lasted 13 yrs 10 months 104,000mi.

The coolant pump seal & cover is only a problem if you have excessive corrosion going on. Mine cleaned up well, no pits, not a problem. Just a fresh seal.
Should be getting my seals and hoses from the dealer tomorrow. When I put the freeze plug in, do I leave it flush with the surface of the head, or recess it a little? If so, how much?
I am also doing the crossover. I got it disconnected on my 97 Deville on Saturday, I am dragging my feet on finishing it up. I don't want to remove the fuel lines and injectors as I just had them off two weeks ago, but looks impossible to clean it all up and remove it without removing the hard fuel rail. I got the new blue seals upper and lower. Wondering if I can get away with the teflon tape on the lower 4 bolts of the crossover. I didn't even know there were freeze plugs back there? Should I replace them, even if I don't have any issues, while I have the cross over out? I replaced a freeze plug on a olds diesel years ago. If I recall right as long as the inside lip was even and flush all the way around, it was good.
MRneatfreak, I've replaced freeze plugs before, at least freeze plugs that go into the block. I've installed them flush to the block, but I figured I'd ask because on the northstar, they don't go in the block. On the northstar there are two plugs on each cylinder head, one on the side, and one in the rear (conveniently located directly behind the crossover). I suppose replacing them while you have access couldn't hurt, but I'm in no way a northstar expert. Now that you mention it, I'm curios too. I only lost one plug, but should I replace the other rear plug while I'm at it? Anyone have any suggestions?
Ok. I just cancelled my order for the crossover gaskets and a few other things at my dealer. I placed the order about 2 weeks ago, first they ordered intake gaskets, and for the past week I've been hearing "should be in any day now" every time I call. I'm done with them. What's the best way to get in touch with Rippy? Pm?
Yeah, a PM or use the contact at the bottom of his posts. [email protected] ph: 800-RIPPY-22
Yeah, a PM or use the contact at the bottom of his posts. [email protected] ph: 800-RIPPY-22
Thanks guys. Chris, I sent you a pm.
MRneatfreak-Teflon tape sucks, avoid it. You can get a small tube of thread sealer at any decent parts store for 2-3-$4.

Tape doesn't work very well on bolts, it's meant for pipe thread that wedges as you screw into a tapered thread.

Tape tends to want to bunch up & just peel off as you screw it in machine bolt thread. A paste or liquid will assure sealer stays in the minor thread diameter. You don't need very much.
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Stock up with a case of your favorite brew, then hit your thumb with a hammer and you will know what a pain this job is. Seriously though, can you temporarily hold each seal on with a loosely secured tie wrap until you get the other bolt into each started a few threads then cut the tie wraps and put the other bolts in?
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