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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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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.

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

Jim Ketcham
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Head photo of coolant plugs.

Attachment: 8DBD5474-DAAA-43C5-9827-BB40D8D9383B.jpeg (Downloaded 149 times)

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 142 times)

Last edited on 07-20-2020 04:55 pm by jensendriver123

Jim Ketcham
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Yes. Those plugs go directly to a coolant passage.

jensendriver123
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Ok. Can you recommend what "sealant" I should use when replacing them?

Thanks very much.

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.

jensendriver123
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Great! Thanks Jim

Richard

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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.

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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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 the 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 128 times)

Last edited on 12-01-2020 02:20 am by Esprit2

Jim Ketcham
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Good catch Tim.

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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.

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.

jensendriver123
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Hi Guys, Haven't been on the forum for a few months. Just now seeing the more recent posts. Well, I had decided Not to pull the head but then one of the cam tower studs stripped out the threads in the head when I was torking it down (18 lbs). That was the last straw. I decided to pull the head and have my local machine shop go through it and install inserts. Now that I'm this deep into it, I'm even thinking about pulling the block so that my shop can balance everything properly. Does anybody have any thoughts on the value of having the engine balanced? I imagine the modern balancing technology has probably made some progress since 50 years ago.

noomg
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Jensendriver,

You're neck deep at this point, might as well go the rest of the way. You can't go wrong having your engine balanced. Think of the spin cycle in your washing machine, what happens when you wash a pair of tennis shoes and they wind on the same side in the spin cycle, the thing vibrates so much it'll literally walk away from the wall.

Esprit2
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Sorry to hear you've run into problems.

FYI, the torque specs in the J-H Workshop manual for the Cam carrier nuts, and for the head nuts are too high. In Lotus' own manuals, the torque specs were lowered, but the J-H manual was never updated.

For the cam carrier nuts, use 14-16 Lbs-ft, not 18 Lbs-ft.

With the original, stock head studs, use...

70 lbs-ft Front & Rear Pairs, Oiled threads.
75 lbs-ft Three Middle Pairs, Oiled threads.

When the Goetze composite head gasket was introduced in Jan 1993, the required higher torque was too much for the original low-spec studs, so new stronger studs were introduced. With the composite gasket, USE the stronger studs, and the new higher torque.

IF you insist upon keeping the original studs, :-( then you have no choice other than to use the original low torque spec, above. That will protect the weak studs, but you won't get the new gaskets' improved performance.

The new torque spec requires the use of a Torque Angle Meter instead of a torque wrench (they're inexpensive).

Cylinder head tightened cold, with oiled threads & washers.
1) 20 Nm (14.75 Lbs-ft) initial preload with torque wrench.
2) +75 Degrees
3) +40 Degrees
4) Wait 5 minutes
5) +20 Degrees
I split #5 up into two steps of #10 degrees each.

if you go with ARP head studs, then use ARP's torque spec along with their own required ARP Ultra Torque Thread Lube on the threads as well as the washer/ nut interface.

110 lbs-ft (15.2 kgf-m), all Studs, with ARP Ultra Lube.

*~*~*~*
Lotus Technical Data Section A (TDA) was released in 1983 for all the naturally aspirated 9XX engines, including the 907, 911 & 912. Torque specs are on the last page.

Every 907 owner should have a copy, and you can download one from my Google Drive, here:

https://tinyurl.com/t7b872hr -- Edit: Replaced link Nov 16, 2021

For more complete torque specs, also download the following Excel Workbook. It contains multiple worksheets, so click on a tab across the bottom of the page to select one. There's a tab for Jensen-Healey. Use the torque specs for the J-H 'vehicle', but I suggest that you use the more up to date Engine specs in the Worksheet titled, "Engine - Lotus 9XX 4-Cyl".

https://tinyurl.com/2e3uzxw5 -- Edit: Replaced link Nov 16, 2021

Regards,
Tim Engel

Last edited on 11-16-2021 07:39 pm by Esprit2

jensendriver123
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Hi Tim,

Wow! Thanks Sooo much for all that good information. I've ordered an engine hoist so that I can pull the whole engine. I've realized, at this point, doing all this work is more than I can manage (and beyond my mental bandwidth) in my own garage with my limited time and tools. But I Can get the block out and get it all over to my machine shop. So, the more information I can get to them, the better. Then, I'll have the comfort of knowing that the engine has been professionally rebuilt (I do trust they are a good shop since they build a lot of racing motors as well as just about anything else), properly balanced etc.

Richard

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If anyone had trouble using the two links in Msg #18 above (something to do with 'Security Changes'), try them again now. I've replaced them both with new, 'current' links.

Regards,
Tim Engel



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