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Please help. Northstar freeze plug.

97397 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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Would the crossover manifold be the aluminum housing that the water pump is installed into? Because that's exactly what's in the way. It looks like it continues over to the other head, or at least somewhat past the throttle body.
Oh god. Any possibility it's accessible through the hole the pump sits in (if I removed the pump)? I just found a picture of the crossover. Looks like it covers the whole backside of the engine, around the throttle body opening and everything. Should I start crying?
Ranger, what's involved in removing and reinstalling the crossover? I can see I'll have to remove throttle linkage, some bracketry, a few hoses and wires etc. I definitely don't trust any of my local mechanics to touch it, and I have a feeling the dealer would have some ridiculous price for the job, think it's worth it? I'm not an amateur mechanic, but I'm not ASE certified either. Is it a hard job, or just time consuming? Thanks.
Thanks everyone.Johnny, I actually read that thread late last night, too bad there wasn't a follow up. I've used those plugs before, not for anything like this though. Im not sure if one of that diameter would be short enough to squeeze between the head and crossover, then add the height of the bolt, I'm not optimistic. Plus, how long do you think the rubber would last in extreme temperatures? 15 degrees on a winter day, then sitting in 230 degree coolant in a matter of minutes, then back again. Sounds rough for $2.00 rubber plug, I don't want to have to replace it every year or two. Plus I'm tired of working on the cooling system, in the past year I've replaced the water pump, thermostat, surge tank and radiator (all ac delco), I don't want to see or smell coolant for the next 10 years.

The other thing is, I don't like to half ass anything, even on an old beater, let alone my own car that I rely on every day. My Seville only has 72,000 miles on it and is in great shape, id rather do it right.

Ok I went outside to look, there's no way I'm fitting my hand down in between there, the gap is too narrow and the hole is too far down. I'd love to just take it to the dealer and have them deal with it, but I just bought and installed struts, strut mounts and spring isolators on all 4 corners, so I'm a bit low on funds.

If I end up doing this myself (most likely) does anyone have any tips or guidance? I already have plenty of tools and have learned many "magic words" over the years. Thanks again.
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Thanks johnny. I've been looking for crossover threads all day, I've seen that one and a few others. The picture in that thread makes it look like there's plenty of clearance to get an expanding plug and a wrench into. In person, it is VERY tight, even with pump removed, it's the crossover itself that's in the way. Besides that I've decided not to go that route, I just wouldn't trust it to last. I think I'm going to bite the bullet, order new gaskets, and do it myself. It's a shame, since there is ZERO trace of any dried dexcool around any of the gaskets. All this work just to spend 2 minutes slapping in a 1" plug. So to you, and anyone else that has done this, Is there anything I should know before starting? Any part of the process that's extremely difficult? I assume the hardest part is keeping the seals in place during reinstallation, am I right? Any info will be GREATLY appreciated.
Silicone hose? For what?
Ohhh, as in silicone heater hose. Sorry, when I read silicone hose I immediately pictured something along the lines of fish tank tubing, confused myself. I've seen the bright green hoses on other Cadillacs, I wasn't aware they were silicone. None of the hoses going to my crossover are green, however the car spent the first 9 years of it's life in Clearwater Florida, maybe they were replaced at some point because of the heat. I was planning on replacing all the hoses while I was in there, I'll make sure to use the right hose. Thanks for the heads up on the harness. I've read that the gaskets go on dry, is it not a good idea to use gasket adhesive? Or by dry do they mean don't use sealant?
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?
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.
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?
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.
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?
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?
Thanks guys. Chris, I sent you a pm.
AHHHHHHHHHHHHH!!!........... Ok I feel better now.

As you may have guessed I started work on my coolant crossover today. I got my parts from Rippy earlier today and started taking parts off and bagging/labeling nuts and bolts. 2 hours later and it's out, 20-30 minutes of that was spent on the 4 lower crossover bolts. It took a combination of a ratchet and socket, 2 different length erections, a universal joint and a low profile racheting wrench, it didn't help that I have huge hands and fingers.

On my journey I discovered a broken vacuum line and pcv hose fitting (maybe I broke them, I thought I was being gentle). Also the trans vent hose was cracked at the nipple on the transmission and very loose. I'll be ordering more parts before I can finish the job it seems. There was one blessing in disguise, 3 of the 4 crossover gaskets were cracked or cracking, so I would have been doing this job soon anyway even if the freeze plug didn't fall out.

I can tell it's going to be REALLY fun getting it back in with the gaskets and lower bolts in place. A few questions so far. I removed the fuel rail (with the injectors still on them). Do I need to lube the o rings before I reinstall them? And what should I use to clean the throttle body and EGR valve? carb or TB cleaner? Any specific procedure for the EGR valve? Thanks.
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Rippy, (or anyone) black, plastic, cylindrical part with a 2 pin connector and one small hose. Attached to the crossover between the plenum and TB, held on with one bolt. Delphi 1997279. EVAP purge valve? If I could upload a pic I would.
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