sachilles

In an effort to not repeat a mistake, figured I could ask for some help diagnosing why the head gasket failed on a 84 944 NA that had a fresh rebuild.
History
Bought the car with a known engine issue believed to be a head gasket failure. Sold to us at price acknowledging the engine issue.
Notes show the owner had rebuilt the engine leads than 1000 miles ago. The head gasket was showing symptoms of failure after the rebuild previous owner chased many little issues after the rebuild only to determine head gasket failure and decided to sell the car rather than try to fix the car.

We brought it home.
Compression was
​​​​​approximately 175 in cylinders 1, 2 and 4. 165 on 3.
Leak down failed on 3 and 4.
Coolant pressure seemed ok at first but later failed. Coolant found leaking on rear of engine on outside of driver's side flywheel housing but no obvious source I could see.

As it's a father son project we took our time taking it apart. All parts seem new, fasteners all seem to come off without a fight. In general consistent with an engine that has new parts and not much run/road time.

Head is off. Below are pictures. No smoking gun to my eyes, but my eyes are horrible and I wouldn't know really what I'm looking at anyway. However, the two Allen bolts were missing by where the temp sensor is. In pictures my finger points at them.

sachilles

Basically curious if folks skip those two bolts routinely for some reason.
A friend said he could see marks from some sort of rotary tool that he suspected was used to clean up gasket material previously.
I'm guessing the head wasn't decked before it was installed previously.

The car will just be a low use street car. Not intending it to be any sort of high performance build.
Head will go a machine shop. Checked, decked, etc. plan to install a lr steam vent kit since the head is out.
Most every thing else seems relatively fresh on the motor, but obviously and gaskets removed with be replaced with new.
One lifter seems a little weak compared to the rest.

Gage

The deck of the head was already compromised by the corrosion pitting. Add in a good round of wiz wheel abrasive pad and you can pretty much expect it to leak.
The two bolts at the coolant transfer port are of course necessary, maybe they just forgot. With the visual signs from this work, one should be cautious to accept the quality of any of the other "rebuild" work reported. The head deck needs to be machined, new gasket, and a good careful cleaning of the block deck as well. Fresh single edge razor blades. held 90 degrees to the surface make a good scraping tool. Change blades often to prevent scratching. No need to waste money on LR modifications. Research and follow the cylinder head tightening procedure.

sachilles

Trusting their work is what makes me nervous for certain.
Confident the machine shop will deal with the head properly.

​​i just need to make sure I do the block side well enough.

Curious why the steam vent kit is a waste.
By history, I'm a Subaru guy, and a similar mod is in fashion. I've used it on my race car, with good results.
Do you consider it overkill, or not worth the effort/cost. Seems like cheap insurance.

Gage

I'm not sure how success or good results would be measured for a mod like this. For me, it's a less is more approach. The kit introduces many new potential leak paths for coolant to escape and is designed to solve a problem that only exists if the original cooling system is not properly filled and maintained.

michaelmount123

Definitely replace the missing 8mm bolts at the front water passage. It will surely leak without them. A fresh deck on your head is good insurance. I wouldn't expect you to have any further problems unless there's some sort of performance chip installed in the Motronic. If there is, take it out and enjoy your ride.

What you don't know is the condition of the block surface. If the engine was severely overheated, the block can also be warped. You can check it (after cleaning) with a proper straight edge and feeler gauges. Consider having the machine shop do it.
MM

sachilles

Early photos from the machinist.

walfreyydo

Looks like you have substantial pitting on that head, I would be somewhat concerned that those pits will allow coolant to creep between coolant and oil passages. The second picture shows pitting that I would think is too close for comfort to the fire ring especially in the area between cylinders. Others may disagree as I have read other threads about pitting and some say its not an issue.

I am dealing with this at the moment with a 968 head I am refurbishing/rebuilding, and I am making the decision to get the pits filled/welded and then have the head resurfaced so its perfect. Just my 2c

What did your machinist say about the pitting?

sachilles

He's not done skimming yet.

michaelmount123

Pitting on the head surface that's outside of the head gasket's cyllinder sealing ring is not an issue. That said, all surfaces under the "fire ring" must be clean and flat.
MM

walfreyydo

What about sealing between the water and oil channels, doesn't the pitting introduce potential for intermix between those ports? True it wont affect compression (although the images above do seem to have pitting very close to the fire ring between cylinders), but my concern is more about the potential for oil/coolant mixing.

sachilles

Wish I took a picture when it was finished. Little to no evidence remained of pitting.
Ultimately.0055 was removed.

sachilles

.....and its up and running. Well sort of😆.
Now that it runs, found some oil leaks to deal with around the oil cooler. Currently waiting on those parts.