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 Posted: 07-20-2020 01:31 am
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jensendriver123
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I've got a coolant fluid leak that I'm suspecting might be coming from the head gasket. It seemed to be coming from the top right front of the engine. But I wasn't able to definitively locate it since the corner of the head was obscured by the water pump hoses. I took the pump off and didn't see any obvious sources from the water pump. So, now, I'm thinking maybe I should just go ahead and pull the head just to replace the gasket. I did check compression and every cylinder hit 60lb on the first turn and close to 135lb after 5 or 6 turns. So, the engine appears to be tight. Does that sound crazy to pull the head when the engine is tight? The car has 48k miles on it. I've got a number of intake valves that are over .008 thousands. So, looks like I should pull the cams to adjust, anyway. Are there any gottchas to pulling the head or is it pretty straight forward? Seems like it should be. And does anybody know how heavy it is? Can I easily lift it out of the car by myself?

Thanks very much.

Richard

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 Posted: 07-20-2020 04:25 am
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discogodfather
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Pulling the head is straightforward enough, there are really no curve balls involved. The cam towers come off and then it's ten nuts. Removing the exhaust can be a pain, depending on the circumstances. The head is light enough to lift off, I think maybe 25-30lbs.

But before you go to the trouble and the cost of a new gasket, why not take some time to think about the coolant leak some more. They sell some florescent dye if it's a difficult to find leak, you add it, let it leak a bit, then look at it under a black light. If you have the original head gasket it's going to yield a slightly higher comp ratio compared to the newer composite gaskets, so you'll loose a half a point on compression.

The water pump has a few bolts and common areas for leaks, I'd start by looking there.

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 Posted: 07-20-2020 12:23 pm
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Jim Ketcham
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CHECK THIS FIRST!
There is an Allen head set screw plug under the bottom lip of the head that goes up into the head that is prone to leak. You will need a dental mirror to see it. It is on the bottom side of the head where it overlaps the block just above the water pump. That leak drove me crazy and I changed the head gasket only to find I still had the leak. Tracking it with dye finally exposed the problem.
I will try to get a picture.
Jim

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 Posted: 07-20-2020 12:31 pm
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Jim Ketcham
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Head photo of coolant plugs.

Attachment: 8DBD5474-DAAA-43C5-9827-BB40D8D9383B.jpeg (Downloaded 59 times)

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 Posted: 07-20-2020 03:53 pm
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jensendriver123
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Oh, yes, I see! And, also, there is another one on the front and it looks like someone has, previously tried to seal it with some silicon. So, I should just pull both of those and clean and replace with some sort of thread sealant?

Attachment: IMG_1916.jpg (Downloaded 53 times)

Last edited on 07-20-2020 03:55 pm by jensendriver123

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 Posted: 07-20-2020 07:23 pm
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Jim Ketcham
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Yes. Those plugs go directly to a coolant passage.

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 Posted: 07-20-2020 07:24 pm
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jensendriver123
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Ok. Can you recommend what "sealant" I should use when replacing them?

Thanks very much.

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 Posted: 07-20-2020 07:28 pm
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Jim Ketcham
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I don’t remember what I used, but Permatex thread sealant should do the trick. Permatex also has a high temperature thread sealant.

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 Posted: 07-20-2020 07:35 pm
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jensendriver123
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Great! Thanks Jim

Richard

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 Posted: 07-21-2020 04:08 am
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discogodfather
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I just used yellow teflon tape when I rebuilt my head a few months ago, works great. Some aviation sealant No.3 is good as well.

Both those plugs are brass and can cross thread easily. They are tapered 1/8" NPT I believe, and you should only use actual plugs, which are available at plumbing places or home depot. If you use some odd bolt, it may block the passage. It's the same passage for both of the plugs, it's designed to clean out the passage on a rebuild. The plugs only go in a few mm's, anything further and it constricts or blocks the passage.

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 Posted: 07-21-2020 11:51 am
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Jim Ketcham
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The plugs in all the heads I have seen are steel. Yellow teflon tape is for natural gas or propane. I personally don’t like using teflon tape as I have found gooey strings of it throughout engines where you really don’t want it.

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 Posted: 07-21-2020 02:40 pm
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Esprit2
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Gentlemen,
Those plugs are for oil passages, NOT coolant. See the attached illustration. The plugs are known to develop leaks, but oil, not coolant.

They were plugged with 1/8 BSP (or BSPT ?), Allen drive grub screws (plugs). The threads were originally sealed with automotive grade silicone sealant (RTV), like the Permatex Ultra series.

I'm not a fan of using silicone sealants in engines, especially in part of the oil system. But given that it would be a challenge to get all the old silicone residue out of the threads, it's probably best to stay with silicone.

Note that the cam shafts are 'gun drilled' full length to deliver oil to the bearings. At the front of the cam, a grub screw is first screwed in full depth and seated. It's threads are sealed with a little silicone sealant, and a little more is smeared over the top. Then when the bolt that secures the cam pulley is installed, it's threads, and the threads in te bore are also smeared with silicone sealant (use a Q-tip/ cotton swab).

Regards,
Tim Engel

Attachment: 9XX Cyl Head - Oil Passage Drillings for Cam Bearing Lubrication - 95kb.jpg (Downloaded 43 times)

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 Posted: 07-21-2020 05:01 pm
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Jim Ketcham
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Good catch Tim.

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 Posted: 07-22-2020 09:30 am
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discogodfather
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It's funny Tim mentions silcone because when I rebuilt my head it had a ton of sludge trapped in those tiny oil passages. I could not get them out, even with high pressure water. I ended by having to drill a hole in the other side of the head so I could use a long stick and push the silicone bits out. The old silcone gets brittle and breaks up into annoying chunks. Then I threaded the hole and plugged it up, so now I have three plugs.

Definitely oil, not coolant. Coolant I would look at the water pump again, there are little bolts holding it on and the gasket originally used is pathetic. I put a new one on with a new water pump and it still leaked a bit, until I was able to tighten it down after some heat cycles.

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 Posted: 07-31-2020 04:36 pm
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noomg
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Jensendriver,

You've got good compression in all four holes, why not try a stop leak product before you pull the head.

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