‘83 944 Smogged and Valve Job

[Dano944]

Recently my 944 didn’t pass smog. My Porsche shop found that #4 cyl had oil. The cylinder head was removed to examine cylinder walls (all looked good), but they found the head gasket had leaked to allow oil in #4. Blown head gaskets seem to be caused by overheating. The shop will change the coolant temp sensor to have the cooling fan to kick in earlier, and they will examine and test the radiator to determine if the radiator is clogged. But here is the question: Did I just waist $$ by requesting the shop to do a valve job? I just figured that since the head is off, why not start with a virtually new head? BTW, I requested that the upper fuel lines be replaced (no extra labor, just parts). My wife said I was an idiot, but that didn’t seem to involve the decision on this repair.

[wwdwgs]

There is a "minimal" valve job and a proper one. Minimal would involve (if the head is not warped beyond the minimal acceptable amount) general cleaning, checking valve stems for "stretch", "straightness", replacing valve seals and "lapping" the valves/seats. The proper one will involve valve guides, probably spring replacement, all of the above with "better" attention to valves/seats, probably, refacing the head and testing (pressure).
Don't worry about wife - MY wife thinks, that I'm an idiot by just owning Porsche.))

[curtisr]

I changed the lower side decal on my 924s to this:

[Dano944]

WWDWGS: The shop will do a proper valve job. Valves, springs, seals, guides, springs…hopefully a brand new cylinder head. My big concern was “why” the gasket failure? From what I know about engines, overheating is a primary cause of gasket failure. The shop mentioned they will do a blow-out of the radiator to determine if it is clear or clogged as well as change the Temp Sensor to get the cooling fans to kick-in more often.

[wwdwgs]

Low coolant could be a problem. I experienced coolant leak (heater hose) and, as a result later on, head gasket failure.. Rather head warpage which lead to a coolant leak into the cylinder (center of 4-cyl engine into cyl #2). That was on Honda with much worse cylinder walls layout.

[wwdwgs]

Dano944, if the rad is clogged and they will clean it, then, I think, there's no need to install a low-temp coolant temp sensor. But, it's up to you.

[Monkey Wrench]

a plugged up rad can indeed cause overheating, so canit if the head has a leak from the waterjacket into the combusion chamber. if this happens it is common to see fluctuations in the water level as the pressure of comporession can backfeed into the waterjacket, thus evacuating it and overheating the head. if this happens you may also see water in the oil (white froth) or oil in the water, or rad water coming ou thte tailpipe accompanied by the sweet smell of antifreeze. You may see issuew like topping off the water bottle and then whan the engine is warmed up the water level doing crazy things like drinking down the bottle or barfing water out because it id getitng backfed because the pressure of combustion is evacuating water from the waterjacket into the water bottle reservioir.

upon emoving the head gasket you may see a cylinder that is steam cleaned and looks cleaner than the others . also look carefully at the head gasket and see if you can see where a part of the gasket has given way. Water which should never enter the cylinder may or may not have been doing just that.

if you have it apart that far, Id agree on having the head rebuilt, hopefully it doesnt; need a new one.

a compression test may reveal some info about how healthy the engine fit is. but of course you can;t do that with the head off. so now you can do a compression test with the ehad back on and if the compression os too low thhen it may cost some time and a head gasket to disasseble for further work.

sometimes people cheap out a bit and don't look after cylinder and ring wear, and then they rebuild a head giving the engine better comporession but with higher compression the rings may leak more and burn even more oil.

that said this is not a "normal" cast iron engine, the aluminum alloy cylinders have a special coating so reboring it to the next oversize, common on cast iron engines may presnet special issues such as having that special coating repplaced. Others here will know more about it and be able to advise better.

replacing just the rings and bearings could be an option but I'd get someone a bit more experienced to advise if you do want to down that rabbit hole.. if the crank is ok then maybe you can just polish the journals or regrind for undersize crank bearings? then would you replace the oil pump too?

the pistons and bores can be examined for scratches when the piston is reversing direction it can "slap" so wiggling the piston around at TDC may show some of that otherwise the bore can be measured with appropriate tools. often there will be a ridge that is formed just where the comression ring reverses direction so that ridge may be a thing for a more experienced mechanic ot look at in order to advise better on the condition of the cylinder bores and piston wear.
If a ring is broken , well you cant really see the rings well without disassembly but you might see vertical scoring lines as a result of broken rings.

Id be careful around the area of the ridge, dont clean it and dont let any grit fall in there. You may set the pistons at about half stroke and put some grease there , then remove it before assembly just in case youdrop grit in there, the grease can catch it. This is so grit is noit getting between the piston and the bore. A theory is that if you clean that area you can loose comoression because the carbon that was stuck there is actually helping.

if you choose to clean the piston tops what I like to do is take a piece of hard insulated wire, (house wiring or romex) bend it into a loop and set it at the top of the piston so if you are cleaning piston tops, you are not tempted to clean , scrape etc, right up to this critical area near the bore If you are not pulling the pistons out.

put plastic over te bores, keep it clean. Id use acetone to clean the head surfaces prior to reassembly. no oil on the head gasket contact area. remve any grease you put there , tunr the engine so a pistons are on the dwonstroke and clean any stuff that was trapped, any small bit of dirt in the ring area can cause scratching upon startiup.



"cheap out" is a poor expression.. This is a major financial and time related decision and to do a engine rebuild or to do a "ring job" One or the other may or may not be your most wise option. hiring a proper porsche mechanic to advise might be a good option even if you do most of the work yourelf.


One of the reasons why we own such cars is to have something to crawl under and hide ;-)

[Dano944]

Monkey Wrench, Porsche shop #2 examined the cylinder bores when they removed the head, and determined they all were in excellent condition. A couple months back I had Shop #1 rebuild the oil cooler, as the coolant recover tank was getting milkshake. Now I wonder if this was a useless $1200 repair when in fact the milkshake could have been cause by the leaking head gasket. But what’s interesting is that my car just recently developed burning oil smoke from under the hood, and Shop #2 determined the oil was leaking from the head gasket o to the hot engine. Thus Shop #2 did a compression check and found Cyl #4 was way below the other 3, and of course, the dreaded head removal. The car should be done in a few days (Yay!). My only regret is that I didn’t take home the valve cover and have it polished.

[wwdwgs]

OIl cooler.... OP, did you look at Clarks Garage site regarding this issue? Just for your information. Oil Cooler can intermix the oil and the coolant. That wasn't a useless repair, just high price for it, in my opinion.

[Dano944]

Originally Posted by wwdwgs

OIl cooler.... OP, did you look at Clarks Garage site regarding this issue? Just for your information. Oil Cooler can intermix the oil and the coolant. That wasn't a useless repair, just high price for it, in my opinion.

In Los Angeles, Porsche labor rates hit $150/hr. And sadly, ALL Porsche model repairs are based on new 911 repairs. I’ve been to 4 different independent Porsche shops, and ALL charge the 911 price for an oil change.,,$350+. Of course this includes a complete “once-over” service and check-up.

[djnolan]

I have heard the 944 engines can go 250k without a rebuild. So if your engine has high mileage maybe it needs a valve job. Maybe it just needs valve guide seals. This could have been the cause of your oil problem on #4. I had a broken inner valve spring that damaged the valve guide seal and caused it to burn oil and foul out the plug. The valve spring and seal was repaired without removing the head. I am not familiar with the head gasket causing oil burning, but I have only owned two 944's. Good Luck!

PS before the head was pulled there could have been a more extensive diagnosis of #4. start with examining the spark plug for oil fouling, coolant fouling or other things. Also look for a milkshake condition. Milkshake in the coolant tank is an oil cooler seal. Milkshake in the crankcase/oil is a bad head gasket. You can do a compression test, and a leak down test and a cooling system pressure test before removing the head. if oil fouling and compression was low inject oil in the cylinder and see if the compression raises such as because of a cracked ring. if the plug is oil fouled it could also be a bad valve guide seal as mentioned. if compression is low and the plug is clean do a cooling system pressure test to see if it might be a bad head gasket or cracked head or block. if compression is low it could also be a bad valve.

Again Good Luck!

[Monkey Wrench]

I think if the cylinders look good and it went low comoression quickly it sounds a lot like a burned exhaust valve., but thats just a gut feeling. The mechanic should advise you about how the valve seats were fitting, it will be easily visible once valve and seats are examined if a leaking valve seat is indeed the case.

If you are getting the head rebuilt now that shoud fix it.if this is true.

sounds ( to me) like shop 2 failed on the head installation causing an oil leak down the block thus oil smoke. maybe the leaked oil hit the hot manifold and created smoke in the engine bay? thats how I interpreted it.

oil does pass through the head gasket so it sounds ( to me ) like that head gasket seal leaked unless soem oil cooler issue was missed, but you seemed to state this was the case unless im reading it wrong.

what djnolan said about the valve seals causing oil burning , yes it can but , that would be smoke out the tailpipe and I interpreted it as smoke in the engine bay, which was it?


. do they stand behind their work or maybe they just charge the flat labor rate even if they mess it up ?
Planing the head , to flatten it if warped, will raise compression and there is a limit to how far you can go unless you resort to a thicker head gasket.There will be written specs on that dimension.
if you have the head you can measure it before and after and know how many thou thay removed.

a good rebuilder won't remove more than necessary but it is possible to have some flunky that sets the thing up for a thick cut and doesnt; put care into what he is doing during his machine setup thus removing more material than necessary to achieve flatness.


if the valve job changes the distance between the slots in the valve stems and the spring lands, this can perhaps afect the spring length and spring compression distance. when you do start driving it again I'd keep a careful ear open for anything that sounds like valve float, a rattly sort of sound evident at higher RPM's , if the valves leave the cam , become airborne, and land this can be disasterous. thats what valve float is. probably the head rebuider will be able to check spring length parameters, but if its sent some general cylinder head jobber shop they could miss that.

the reason I mention it is I had the seats replaced in my volvo 122, I had them install stainless steel seats and do a proper 3 angle valve grind and fit ( knurl and ream) my newly installed valves and guides. I polished the ports myself but that is irrelivent. the head work was decent but I did the installation of springs myself and I messed it up a little. a learning experience.

Now that was an entirely different engine , not an overhead cam design, its an old tractor engine basically. Anyway it destroyed my cam and lifters. I actually removed a push rod and drove the thing home, 200 K on 3 cylinders with a spark plug removed and then tore it down it ate one cam lobe and one lifter.

after replacing the cam and lifters, it already had new springs. the problem was that my valve seat installation changed the distance from the spring land to the valve keeper slot. only by a few thou.

this affected the spring length and they appeared ok but my springs were not compressed quite far enough. upon use i heard the rattly sound in time and correct it it by adding shims under each spring without head removal.

paying attention to the sound and quick correction of the issue saved my second cam and lifters from destruction.

the overhead cam in a Porsche does not have push rods. it is completely different in design you can see the cam lobes easily. I don't see why similar issues with valve float could not happen in any other engine.

what suprised me in all of this is that although the valve springs were not bound up and they did extend fully without any evindent looseness that distance proved very important. after I added just a few thou ( washers under the springs) then it could rev past its redline with no valve float. I had the engine balanced. they took the rotating parts and did their thing, it wasnt; that epsensive, Id do that agein.

I checked with paper strips that the valve springs were not becoming coil bound.


I could stand corrected by the porsche engine experts here , which I am not. all im saying is when you do get out out on the road listen to it. If it doesnt; sound right let them know. maybe the mechanic will put it on a dyno or take it for a proper run and let it see the redline.

I was advised on how to drive it after cam replacement , not sure if this is important, maybe ask the others that. If its just a head job then you aren't breaking in a new set of rings. in my underhead cam engine I was told that the lifters have to spin and if they fail to , they won't break in right. I had my original cam weleded and reground for higher lift and the camshaft expert gave me a special lube for this break in step. it was redesigned but to a bit higher cam, to an OEM volvo cam spec, not a radical one. my second cam I just bought as new. I first figured the welds had failed but it was actually the springs that created the issue, not his work.

iI am not sure on the 944 but on a lot of engines it is normal practice to torque the head and then get it properly warm and then re-torque, others can advise better on the correct procedure but maybe failing to do that second torque could cause a leak. others here will speak from more experinece. the proper torque procedure will surely be in the repair manual.

lets hope it is ok after all that time and expense.

if you are sending a head out for valve intallation or grinding , Id first measure the distance from the head surface to the top of the springs, if it comes back different it could mean the valve spring length got altered.

as you do a valve grind, because of material removal, the valve goes a litle deeper into the head this changes the length of the spring. reduces the tension.

if you send a head out to have a shop install seats or different valves the valves may move slightly the other way. Id just take measurements before aand after to be able to percieve what difference the head work made to the valve spring ( or valve stem) length.

if you or the mechanic can measure the before and after distance, its very easy to see what dimensional change was made by the head work that was performed. I would not send a head out withtout measuring that, only takes a few minutes.

if the head shop puts washers under the springs, Im not sure if you can see that with the valves reinstalled.
They may or may not be careful enough to know this , and to compensate? it may be quite normal for the rebuilt head to come back with the springs stem seals and keepers, already put together.

[djnolan]

the cam carrier seal between the cam carrier and the head is a likely cause of oil leak. there is also a small round plate at the back of the cam carrier that can go bad easily since it is a cork seal. either makes a mess!

[walfreyydo]

I would think that if you had a head gasket issue, you would see coolant in the cylinders as opposed to oil. The reason is that the cylinder is wrapped by a cooling jacket that only contains coolant. There are no oil passages that could leak into the cylinder without first having to go through a coolant passage/jacket, likely leak into the coolant system and cause a "milkshake" condition in your oil before it got to the cylinder...

A good shop would also run a coolant pressure test and run a test on your coolant to identify the presence of hydrocarbons - which would prove that there is combustion gases getting into the coolant, ie, headgasket issue. A compression test does not always reveal issues with a headgasket, especially if its a small leak.

As mentioned previously, if you have oil in the cylinders, the more likely cause is valve guides and valve seals. You should ensure the shop is going to replace those as part of the head refurbish job... Another source of the oil could potentially be piston rings, and that would be picked up in a compression test showing low compression on that cylinder.

To me, its a bit troubling if the shop hasnt taken the proper steps/tests to verify head gasket issue (again these are simple tests) and now chasing down rabbit holes with your radiator and fans... Regardless, if the issue is leaking valve guides/seals, a new HG will need to be installed anyways. Just ensure they are replacing the valve guides and valve seals as part of the head job (as well as cut and grind seats and valve faces, check springs, check valve stems, check lifters, head resurface and check the block deck for warpage)...

Below is a diagram showing the coolant areas (blue) and oil passages (green) and you can see plainly why oil getting into the cylinders due to a headgasket failure isnt likely, because it would have to get past the cooling jacket (and again you would then have oil mixing with your coolant, ie: milkshake oil)

[Dano944]

The shop did a compression check, then sent a scope down into each cylinder to examine and found oil leaking from the head gasket. After removing the head, found the gasket was bad around #4. After the failed Smog Test (high hydro carbon), I immediately took the car into the shop. Basically only 5 miles driven to the shop, so maybe not enough time for milkshake in the engine oil? The dipstick and oil fill cap both looked clean. As mentioned, the shop examined the piston cylinders and found all were perfectly fine. As mentioned, the head is off, so I authorized a complete valve job. As mentioned, to help pinpoint causes, shop will do a pressure blow out of the radiator to determine if the rad could be clogged. Of all the shops who have serviced my 944, and who I have paid $$ to learn how to fix a 944, the current shop has technicians who drive 944’s, so I have great faith in their knowledge of these forgotten cars. Oh, besides the many variations of 911’s they repair, they also work on 928’s. This shop gets extra kudos for working on 928’s.

[Monkey Wrench]

walfreyydo that was a great post, not all engines have such a large opening around the cylinders. the graphics helped make it more clear,


by comparison here is a 80's volvo head and block, the comparison shows lot less open waterjacket surface area.

.

[walfreyydo]

Thanks MW, my post and info was specific to the 944, but you are correct, different engines have different block designs and there are certainly configurations where oil can leak into the cylinder due to a bad HG.

Just dont see how it can happen on a 944

[Monkey Wrench]

yes exactly, My point was just to reinforce what was said. You can see how in the volvo ( or many other engines) a head gasket failure coudl result in oil bridging into a cylinder bore whereas in Walfreyydo's example this looks physically impossible. in the instances Ive seen the water got into the piston bore, water out the tailpipe, fluctuations in water level at the bottle, engine overheating. head wasnt; warped the ring around the piston suffered a breakdown. I think over time the ring can just break down due to corrosion. so long as its caught in time no other damage but if driven too much overheating caused by water being pushed out of the head by way of comoression acting upon the waterjacket may then warp the head. in this example I installed the gasket, did a full engine rebuild had the head reconditioned, 20 years after, without a lot of miles, the gasket itself failed, the head was not warped. It only needed a gasket set. being a little over zealous I bored the block .030 over, new pistons. It still has great compression.

the car is a bit of a beater, Just a spare car. so I experimented the Bar's head gasket fix stuff, it almost worked, The stuff was actually bridging the gap in the ring with a hard material.
Theres a few different types, the one I chose requires draining and flushign the coolant, then it is put in and run through several heat cycles, then it needs to be flushed again and the antifreeze added.
its the sort of thing one may do if the car isnt; worth the labor and the owners next step is to call a tow truck and scrap it. I wouldn't even think of it in a car that's of any value. It was just an interesting experiment.

[Dano944]

So…oil leaking from my cylinder head due to a bad gasket seems impossible, or just impossible that a bad gasket would cause oil leaking into the cylinder? And if oil was found in #4, that could only have been caused by a bad valve/seal? In either case, I’m getting a new gasket and new valves/seats/springs and a polished head. It’s only money.

[Monkey Wrench]

are you sure it was oil and not fuel? a stuck open injector can cause the fuel rail pressure to empty into a cylinder, then upon startup maybe after sitting overnight, you may see a white cloud of smoke for a few blocks, then normal operation.

if you suspected this you might try to check the injectors or maybe just move them around while its apart and you have acess.. if that were the issue the head rebuild would not solve it.

how about ask the mechanic to swap injector 4 and 1 while its apart? if the problem moves when it gets going, that says something. they are likely sitting there now on the fuel rail and it is detached.

if he connected the wiring to the injecotrs grounds) turned the key pn for a sec, it would build fule rail presure and if the #4 injector squirted gas that proves it is stuck (there are dangers involved in doing htis)

oil may cause black stinky smoke, fuel may cause white smoke.

to check for that you can connect a fuel pressure guage , turn the engine off and watch if the pressure in the fuel rail can hold, if it leaks down can be a stuck open injecotr or maybe a bad check valve ( near the fuel pump)

what Ive done ois to test the injecotrs out of the car, or pull the fuel rail loose , and watch if it shuts off ( not often recommended in a manual , due to danger of fire or explosion)

anothr wayy is to move the injectors and see if the issue moves with the suspect injector

what I saw was if I drove the car the plug cleared itself up, but if it was getitng soaked with gas, then it appeared black and very dirty looking.

one could probably just pull the plugs if it was a stuck injector the plug might stink of gas. but if you drive the car nd it clears itself it may look normal.



I once stuck a valve with a bigger stem in a junker, the exhaust valve had a hunk missing so it would not run. I machined the valve that wasnt; even from the same car to close enough , lapped it in I picked the closest drill bit and drilled the guide, lol no reamers.. ;-)

the car ran but had a mist of oil following it and used a quart in about 10 miles, lol

your car is apart now so its too late,

What a mechanic could do is hook a compressor to the plug hole. I made my own tool up by knocking the guts out of a plug and pressed in a tubeless tire valve. I took the tire valve to a grinder and reduced the size of the rubber til I could press it in there.

then put compressed air in the bore, listen to see where it leaks, ( leakdown test ( careful engine may turn)

a bad giuide or broken piston or bad valve or bad head gasket may possibly be diagnosed by listing to where the escaping air is going. I guess you could add colored air ( smoke maybe)

wiht the engine apart that test is of coure, impossible .