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Thread Title:

'Diamond' seal question.

Created On Wednesday December 02, 2009 18:54

olered

Posts: 103
Joined: Dec 2008

Wednesday December 02, 2009 18:54

I have a cam thrust plate 'diamond' seal leaking up front pretty bad with only about 50k on the motor. I was hanging around when the motor went together and I'm pretty sure that seal went on dry. Is there any special way this seal should be dealt with, as in using RTV or something similar? It did not leak for the first couple of months after the motor was finished, but now leaks pretty good. I did put the driver and passenger side bracket(s) on that attach the head to the front cover. Didn't change anything.

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GoneFishen

Posts: 1325
Joined: Jan 2007

Wednesday December 02, 2009 21:21
Installed dry, use new cam bolt. Also replace the perimeter seal at the same time. Have seen a few where the inner bolts were not torqued up and this allows the seal to not have a good contact with the head. Was the head also clean? ------------------------- DDA tech for 30 years,all 2 cycle,series 60,50 mbe also. 1995 F250, 191k mi. Lost Wages, Nv

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olered

Posts: 103
Joined: Dec 2008

Friday December 04, 2009 14:21
Thanks GF. Yes the head was a new reman and it was clean. I believe there may have been a little bit of grease just to hold the seal in place. When you say perimeter seal, are you referring to the front cover seal?

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GoneFishen

Posts: 1325
Joined: Jan 2007

Friday December 04, 2009 21:11

The diamond seal is the one that actually contacts the head casting. The perimeter seal os the one around the shiny round metal thing that the diamond seal is set in. We do both on a rebuild. Standard procedure. Make sure that it is the diamond seal. I have seen a rocker gasket installed w/o the silicone on the cam cam [even the seal missing under the cap], and it just looks like the diamond seal.

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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olered

Posts: 103
Joined: Dec 2008

Friday January 01, 2010 19:07

Well to give an update as well as ask more questions... I had the diamond seal, perimeter gasket, and the rocker Cover gasket replaced for good measure. They all were in good shape with no signs of leaking. I had also bought a couple of the o-ring type seals like the one that goes under the front cam bearing cap. He did not replace this. DUH I told him!! Well the leak is still there. Could the cam bearing cap o-ring be leaking to make it appear to be the diamond seal? I looked at another cylinder head like mine to see if there were any plugs or such on the front of the head that would cause an oil leak. Nothing that appeared to be in the oil galley.

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BUTCH

Posts: 256
Joined: Jan 2009

Friday January 01, 2010 19:42
the front cover cracks right where your saying its leaking,its real common,its also expensive ------------------------- IM A 35 YR OWNER OPERATOR

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olered

Posts: 103
Joined: Dec 2008

Saturday January 02, 2010 09:35
I sure hope it is not the front cover because you are right about the expensive part! After cleaning it off and letting it run 1500 rpms or so for about 15 minutes, you can start to see the leak. It appears to be coming from the head rather than the front cover. Has anyone here ever heard of a cylinder head cracking up front?

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GoneFishen

Posts: 1325
Joined: Jan 2007

Sunday January 03, 2010 10:39

Just the gasket leaking. Spray a real good cleaner in that small area between the head and cover Dry it real good. Use pleanty of time and wash that good. Hard to see what is happening there. I use brake clean after I pressure wash the area. blow dry real good. Then I start and run at fast idle or put it on the dyno with another operator. I use a good flashlight and watch on the RH side between head/cover. If it is the cover cracked think$$$. head gaskets are a cheaper leak. A DDC authorized shop guarantees work for 90 days and parts for 1 year.

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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olered

Posts: 103
Joined: Dec 2008

Sunday January 03, 2010 12:19

I'll give it another good cleaning and do another inspection the best I can. It's only 12 degrees here, LOL... I'll get out the jet-beam flashlight!! GF, you are saying to try and inspect more from the passenger side up top?

The engine only has 55,000 miles on it since last February. There was no sign of leakage until 2 or 3 months after the rebuild. It was bone dry one day and the next it was leaking. I pull up the hood atleast every other day so I get a good visual several times per week to see if anything strange pops up. I had to wait until my dedicated deal was down a full week before I could finally get it into the shop to take a good look at it. I even had it ran on the dyno at a Clarke shop locally to try and pinpoint the leak 2 months ago. Shop manager said it was diamond seal. That obviously wasn't it.

One a side note, $250 later and the Clarke dyno could only hold water pressure up to 481 hp at which my truck was still 'just cruising'. That was the operators words. I was a little ticked since I also wanted to see what dyno number the truck would put up. With no satisfaction from the shop manager, I went to a Cat dealer in town who also has a chassis dyno. To my satisfaction, 531 hp was the magic number!! The Clarke shop manager called me the day after I was there wanting to know where my ecm was from...

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joeturbodiesel

Posts: 21
Joined: Aug 2009

Monday January 25, 2010 22:10

I overhauled a 12.7 once and had a leak there. What happened to me was the oil from the cam cap in front was leaking oil from the bearing area to the front of the cap. there is a blue oval ring there but you also have to put sealer in the corners of the bearing cap to seal it off completly. Well there was a microscopic area without sealer and it leaked until I pulled off the cap and put sealer on it again and get the spot I missed. I have also found the long stud that holds those caps down where the rocker shaft goes loose also. That will let the cap up and leak oil. Just some suggestions.

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GoneFishen

Posts: 1325
Joined: Jan 2007

Tuesday January 26, 2010 20:43
Joe's suggestion is well worth checking. The correct sealant and proper placement of it is definatly critical. Go that route first. The stud he mentioned should have a 'rubber based 'washed under the seat of the rocker stud. Keeps the stud from loosening up. ------------------------- DDA tech for 30 years,all 2 cycle,series 60,50 mbe also. 1995 F250, 191k mi. Lost Wages, Nv

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olered

Posts: 103
Joined: Dec 2008

Sunday January 31, 2010 07:02

Just as I was finally getting back to update my oil leak situation, I see Joeturbo and GF hit the nail on the head!! A few weeks ago, the truck was in the shop and they replaced the diamond seal, perimeter seal, and went ahead and put on a new rocker cover gasket. I had specifically asked them to go ahead and check the front cam cap. When I went to pick up the truck, it was still leaking and my mechanic said the damn thing is still leaking dripping down the front of the head. I asked if he'd replaced the cam bearing cap seal, and he said no and that where the leak must still be coming from. I'm thinking well no shit sherlock. The following weekend, they pulled it apart again and replaced the small oval seal and use plenty of sealer. NO LEAK! He also said that around the hole the small oval seal goes around(oil port), it looked as if either during the casting of the head or in the reman process, there is a small circle shaped indentation that practically goes through where the oval seal goes. Sort of a defect as it looked like it shouldn't be there. Not sure of that one...

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GoneFishen

Posts: 1325
Joined: Jan 2007

Sunday January 31, 2010 10:32

If that is a reman head they take the old stle casting and drill the old style round area out. Then they install an insert in that cut area. Then the camcap is cut for the new seal. Hopefully they also instaledthe rubbercoated washer also on the rockershaft stud. Glad to hear itis fixed and you are running again.

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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