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6G Celicas Forums > 6th Generation Celica > Engine/Transmission/Maintenance
Langing
1994 Celica ST, 1.8L, Manual

Rebuilding the engine after 300,000 miles and an overheat incident. Need information that isn't in the BGB.

Trying to reassemble the IIA (distributor) into/on a 'remanufactured' head. The part of the assembly that goes into the head goes through a largish circular hole, and there is a large O-ring (distributor O-ring?) riding in a square cross-section groove cut into the IIA that supposedly seals the hole so oil does not escape from the head.

Some places I have read that the O-ring should be 'lubricated', but there is nothing about that in the Repair Manual (the big Green books). I had an unpleasant experience when I rebuilt the disk brakes a couple of years ago. Because of the 'lubricant' I used on the slider pins, the rubber ring absorbed something from the grease and made it swell such that the pins stopped sliding. Am I about to do something stupid again if I 'lubricate' this O-ring? And, what 'lubricant' or grease should be used to make that O-ring create a proper seal?

TIA
Box
Let it soak in motor oil for a few hours before installing, can take a little bit of what your going to fill the engine with after rebuild and do it in a Ziploc bag or small plastic cup.
Bitter
Engine oil or silicone grease, either will work to lube the O-ring, I prefer silicone grease cause it's thicker and will stay in place when you're stuffing it in better.
Langing
Thank you for the help, box and bitter. I continued looking on-line yesterday and found a handbook on o-rings and seals that I found overwhelming, considering that I got the O-ring in an engine rebuild kit so have no idea what material it is. It is called 'The Seal Man's O-Ring Handbook - Harvard Physics' and is packed with information that depends on knowing its material.

But I found it interesting that this source cross-references the compatibility of O-ring material type with thousands of different chemicals. Silicone seems not to effect O-rings of almost any material.

This handbook also is useful for explaining the various failure modes of O-rings, and how o deal with them.

Thanks again for your useful advice. It really helps to be able to turn to experts as I move from one uncertainty to another that I have never dealt with before, while rebuilding this engine. This is a FIRST for me!
Bitter
If its in an engine on a distributor shaft then it's made for contact with oil so you can lube with whatever it's supposed to seal. Lube brake piston rings with brake fluid, lube, lube cooling system hoses and seals with coolant, lube engine o-rings with oil (except fuel system O-rings, lube them with...a sparing amount of silicone since silicone is bad for O2 sensors)
Langing
Thanks Bitter, that's yet more good, useful information. It is helping me, so thanks!

Now comes my confession:

At the head of this thread, I claimed there was no instruction in the BGB that described 'lubrication' of that distributor O-ring. I WAS WRONG! I was going by the 'other' reference (one of TWO) to reattaching the distributor onto the cylinder head.

Today, when I went at it again, I discovered, in the IG (ignition) section of Volume 1, 'IIA INSTALLATION':

1. REMOVE RIGHT HAND ENGINE UNDER COVER
2. SET NO. 1 CYLINDER TO TDC/COMPRESSION
blah, blah
3. INSTALL IIA

(a) Install a new O-ring to the distributor housing.
(b) Apply a light coat of engine oil on the O-ring.
© Align the cutout portion of the coupling with the groove of the housing.
(d) Insert the IIA. aligning the center of the flange with that of the bolt hole on the cylinder head.
(e) Lightly tighten the two bolts.

The procedure continues to add back the spark plug wires, the two IIA connectors, the negative terminal of the battery, then warm up the engine, connect a tach and timing light and set the timing of the engine before tightening down the two mounting bolts. (15 ft-lbf).

I apologize for unnecessarily bothering you helpful people. I have owned the (2) manuals for over 10 years, so you would think I should be able to read them by now, but I must have been rushing and failed to dig out the procedure to remove and replace the IIA. I knew about the (IG) ignition chapter being separate from the main engine details because I had been back there using the procedure to test the resistance of the primary, secondary and pick-up coils, because I wanted to know the unit was as sound as possible before reinstalling it after cleaning.

That being said, and considering Bitter's additional information, I notice that the O-ring that came with my engine rebuild kit (it fit the distributor housing) fits in a groove, and when installed is the largest OD of the distributor housing, so seals the hole it uses to penetrate the head. Before installing IIA, that O-ring does not take up all of the space inside the groove. Is that extra space in the groove used when the O-ring is squeezed to make the oil seal? I am asking because Bitter first recommended using silicone grease which is more like a filler (to me) and I had thought it might fill the gap I noticed in the O-ring groove. If the O-ring squeezes under pressure to fill the groove, then motor oil would make complete sense to me.
Bitter
The O-ring should stick out a little fatter than the shaft to seal, maybe you got the wrong o-ring on the distributor?
Langing
It does. . . by more than a half mm. OD (O-ring)-OD (shaft) > 0.5 mm. But the unused space visible in the groove is an appreciable fraction of the full O-ring thickness distance. If I knew how to post a picture, I would love to show you what I mean.
Box
Will have to upload to a hosting site like Photobucket then embed the url link.
Bitter
QUOTE (Langing @ Jun 12, 2017 - 10:17 AM) *
It does. . . by more than a half mm. OD (O-ring)-OD (shaft) > 0.5 mm. But the unused space visible in the groove is an appreciable fraction of the full O-ring thickness distance. If I knew how to post a picture, I would love to show you what I mean.

I think I understand what you mean, the groove is wider than the O-ring, sometimes that's OK cause the rubber compresses and fills the groove. Usually the O-ring is more closely matched to the groove width...usually.
Langing
Ok, Box, that brought back many memories (Photobucket). . . and reminded me why I cut my cableTV cable. . . but, now I believe I can show you exactly how the O-ring looks mounted on the distributor housing. It might be helpful for you to see a picture. Maybe I installed an incorrect O-ring. Who knows?



Measured the OD of the O-ring and it is > 0.5 mm larger than the nose of the housing. Seems to me when the nose is inserted into the orifice of the head, the O-ring will be pushed to the rear of the channel and be squeezed by the narrow orifice. When squeezed, I can imagine it would compress somewhat inward (toward the right in this photo), but I cannot see it completely filling that channel. You might be able to see a bit of scarring on the O-ring from my first attempt at assembling the IIA to the head without lubricant.

My concern here is that it is supposed to seal oil flowing past the O-ring, to the left, and without the O-ring completely filling the channel, there could potentially be oil covering a fair amount of the surface of the O-ring, as it filled in whatever empty space there might be in the channel. Maybe I should purchase another O-ring that I know was made for the distributor housing and compare them? Or, I could simply stop obsessing, and wait until I find an oil leak at the distributor end of the head after the engine has been reassembled?
Bitter
Yes, it's an easy leak to fix later so I'd give it a go.
Langing
Thanks for sticking with me, Bitter. Learning how to do all of this is sometimes overwhelming, and people like you and Box sure do help take the fear out of the process. Now, onward to the next step, how to calibrate my cheap torque wrenches, so I will be ready to reassemble the engine when everything is ready.
Box
Does seem a little thinner than it should but it could be fine, I'd soak it in oil so it'll go ahead and do any swelling then you can wipe it off and apply silicone grease before installing.
Langing
Thanks for the advice, Box. I believe that is exactly what I will do, but first I think I am going to run to my local Toyota dealer and see if I can get an OEM O-ring to try on and see if it looks anyway different. That is, if it doesn't cost more than I can afford.
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