When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was dealing with a nasty oil leak from passenger side of engine since I acquired the car about 2 years ago. I initially thought that oil leak is coming from cam tower. But when I disassembled the engine, I found that leak is actually coming from head gasket as shown in the pictures below. In the first picture, oil seems to be flowing down from cylinder bores and going over the top of oil cooler housing.
I never did a head gasket job before, so I am not sure what caused this extensive leak. Is this a head gasket failure or may be the nuts on the passenger side were not torqued down properly? Or is there any other reason for such a leak? I want to avoid any missteps when installing new head gasket so any tips would be helpful. Thanks.
I would check the head sealing surface and block surface for any deep gouges or pitting. Your local machine shop can help you evaluate the head surface as well. Although its not 100% required if the head sealing surface is smooth and doesnt contain any warpage (warpage can be checked with a machinists straight edge and feeler gauges), its still a good idea to get the head resurfaced before reinstalling.
Now would also be a good time to potentially get the valves ground, valve seats re-cut and replace valve guides and valve seals. Its also good idea to check the valve springs and valve stems for wear tolerance and replace if needed.
In terms of the oil leak, it could be a result of a worn out head gasket, gouging/pitting in the head surface, or head warpage.
Last edited by walfreyydo; 08-14-2024 at 09:48 AM.
Yes, I am heading over to the machine shop tomorrow. Plan is to install new valve seals, guides and valve springs as well. Since the oil is flowing over the gasket, it's probably the upper metal surface which was not maintain a tight seal.
I was wondering, would it help to lay down a very thin coat of Permatex anerobic sealer on those mating surfaces, before reassembly?
I have personally never used anything on the block or the head to aid in sealing at the head gasket area. The head gasket weakens over time and with heat cycles. I would just make sure that the block is clean and dry before installing a new gasket onto the block. If there is pitting once the old oil is cleaned from the block, we can reevaluate at that time.
You said you are taking the head to a machine shop, which is for the best. Make sure they go through it and mill it if necessary.
I would not use any form of sealant. Follow the factory procedures listed in the FSM, ideally get the head resurfaced, or at the very least measured to confirm its within spec, nothing more.
Also, you can't be sure where any defect might be by assessing which gasket oil is flowing under or over. These surfaces are under immense pressure and any defect could be in multitude or not adjacent to the gasket borders as you might imagine.
Chances are that the block will be just fine once you clean it before reassembly. The last 944 head that I replaced had a block that looked similar. I wiped the surface with a rag soaked in brake clean and removed any left over gasket deposits by hand with a piece of red scotchbrite pad. The block deck surface looked nearly brand new before assembly. Once it was clean, I checked the deck in four sections with a straight edge and there was no warpage of the block.
The head came back from the machine shop after being hot tanked, surfaced, and had the valves replaced and lapped. Just remember the proper head torquing procedure and follow it closely. I do recommend replacing the head nuts and washers as well.
BTW there is only 1 point in the head gasket that is exposed to high pressure oil. That is a small round hole near the rear, where there is an oil passage from down in the block up to the cam tower. There are several large rectangular openings that allow gravity return of oil from the cam tower to the sump. These are not under any pressure and for them to be leaking, the gasket would have to be in very bad shape. The head gasket is of course exposed to the high pressure combustion gases, which should not be oily, and to the low pressure coolant that surrounds the combustion chambers. Regardless, your eyes don't deceive you, something doesn't look right and the above suggestions should be followed up on.
There are commercial products that you can use to test the coolant to see if the coolant has combustion by-products in it.
08-14-2024, 12:52 AM
Head Gasket is leaking oil from multiple points.
