Blown head gasket on a 944?

[Jaime0511]

Hi, I’m sure I have a blown head gasket. I have a rough idle for about 1 minute after cold start and when I accelerate in park white smoke is coming from the exhaust. Goes away after a few minutes and no more smoke.

Car doesn’t over heat and coolant seems fine but maybe a little loss.

Any other symptoms to look out for?

And how long can I drive the car without fixing it?

Thank you for your help in advance

[944 Ecology]

Originally Posted by Jaime0511

And how long can I drive the car without fixing it?

You should fix it now, not after you compromise the oil/coolant interface and have to replace all the crankshaft bearings.

Park it until you have the time and money to fix it right.

[wwdwgs]

HI,
you can smell coolant - it should not smell like burnt gases or have any oily film on top.
Also, smell the motor oil and check it visually.
Also, unscrew the plugs and peek inside (a borescope will help). If there's a presence of coolant - bingo. If one (or two) cylinder is extremely clean and shiny - bingo.
Also, pressure test each cylinder - ask other how to do that?
I drove (another 4-cyl car) about 50 miles when I first encountered blown gasket. Surprisingly, the car drove fine and the engine work on all 4 cylinders until I reached my home.
Comparing to other (modern) 4-cyl engines, Porsche watercooled 4-cyl have better cooling design around each cylinder, better exhaust manifold design, therefore the head warpage is less likely to happen.
Looks like you have a minor coolant leak, if smoke disappears soon.

[OK-944]

Does that white smoke have a slightly sweet smell? If so, this is a good indication that indeed, there is coolant entering one or more combustion chamber - and should be addressed as soon as possible.

Is this (white smoking on startup) a recent phenomena? Has the weather changed recently? I ask because especially on cooler mornings its not unusual to get a bit of white exhaust on startup…which will then dissipate as the engine warms and any naturally accumulated moisture within the engine gets vaporized. So if there is white smoke upon startup but this does not smell sweet, you’re probably OK.

Also…look at (and squeeze) the top section of radiator hose as it exits the water neck at the front of the engine. A failing head gasket can cause overpressure which can cause this section of hose to enlarge or “balloon” slightly.

A number of years ago when I was into Saabs, I’d looked at a 1996 900-S which looked to be in pristine condition - but something seemed off during the test drive. Engine felt a bit rough and underpowered, and while I did not smell anything sweet emanating from the exhaust pipe, I did find an upper radiator hose to have “ballooned” rather significantly…so I walked away from what otherwise had seemed like a great car for a good price.

Another area of concern in a 944 is the oil cooler…and its not all that uncommon for either the large gasket under the cover, or a smaller internal O-ring, to fail due to age or misalignment - leading to a coolant-oil mix.

If the coolant in your plastic expansion/filler tank suddenly starts to look brownish, this usually means that oil has found its way into the coolant. Not as serious as coolant mixing with oil (which causes the “sweet smelling” white exhaust) - but worthy of quick attention just the same.

[Jaime0511]

Originally Posted by wwdwgs

HI,
you can smell coolant - it should not smell like burnt gases or have any oily film on top.
Also, smell the motor oil and check if visually.
Also, unscrew the plugs and peek inside (a borescope will help). If there's a presence of coolant - bingo. If one (or two) cylinder is extremely clean and shiny - bingo.
Also, pressure test each cylinder - ask other how to do that?
I drove (another 4-cyl car) about 50 miles when I first encountered blown gasket. Surprisingly, the car drove fine and the engine work on all 4 cylinders until I reached my home.
Comparing to other (modern) 4-cyl engines, Porsche watercooled 4-cyl have better cooling design around each cylinder, better exhaust manifold design, therefore the head warpage is less likely to happen.
Looks like you have a minor coolant leak, if smoke disappears soon.

Thank you I’m going to check the plugs once I’m home (currently not driving it) and also do a pressure test.

What will you recommend of changing if I do do the head gasket replacement? Water pump and timing belt was changed 7 months ago

[Jaime0511]

Originally Posted by OK-944

Does that white smoke have a slightly sweet smell? If so, this is a good indication that indeed, there is coolant entering one or more combustion chamber - and should be addressed as soon as possible.

Is this (white smoking on startup) a recent phenomena? Has the weather changed recently? I ask because especially on cooler mornings its not unusual to get a bit of white exhaust on startup…which will then dissipate as the engine warms and any naturally accumulated moisture within the engine gets vaporized. So if there is white smoke upon startup but this does not smell sweet, you’re probably OK.

Also…look at (and squeeze) the top section of radiator hose as it exits the water neck at the front of the engine. A failing head gasket can cause overpressure which can cause this section of hose to enlarge or “balloon” slightly.

A number of years ago when I was into Saabs, I’d looked at a 1996 900-S which looked to be in pristine condition - but something seemed off during the test drive. Engine felt a bit rough and underpowered, and while I did not smell anything sweet emanating from the exhaust pipe, I did find an upper radiator hose to have “ballooned” rather significantly…so I walked away from what otherwise had seemed like a great car for a good price.

Another area of concern in a 944 is the oil cooler…and its not all that uncommon for either the large gasket under the cover, or a smaller internal O-ring, to fail due to age or misalignment - leading to a coolant-oil mix.

If the coolant in your plastic expansion/filler tank suddenly starts to look brownish, this usually means that oil has found its way into the coolant. Not as serious as coolant mixing with oil (which causes the “sweet smelling” white exhaust) - but worthy of quick attention just the same.

No I don’t smell no sweet smell.

Probably id say the last month or so, I don’t drive it too often so never really paid close attention.

I’ll do radiator hose trick once I’m home and the coolant still looks normal. I’m going to fill it ip to spec and see if it’s losing coolant.

Also, what will you recommend I change as well if I do end up doing the head gasket ? Timing belt and water pump has been changed 7 months ago.

[wwdwgs]

If you'll work on the head, think about these (if yours is early 944, not 16-valve)
front end seals
oil/coolant radiator gaskets
Check oil pressure relieve valve
intake, exhaust gaskets
cleaning or servicing fuel injectors (maybe new o-rings)
check idle control valve and it's hoses
check rubber posts that hold idle control valve (2)
check / replace oil tube o-rings
inspect engine mounts
camshaft housing gaskets
upper "cooling socket" gasket

EDIT:
check balance shafts/cam shaft "spacer sleeves", they may have deep grooves from old seals.

EDIT: do you have PET parts catalog? If not, download it from HERE.

[Jaime0511]

Originally Posted by wwdwgs

If you'll work on the head, think about these (if yours is early 944, not 16-valve)
front end seals
oil/coolant radiator gaskets
Check oil pressure relieve valve
intake, exhaust gaskets
cleaning or servicing fuel injectors (maybe new o-rings)
check idle control valve and it's hoses
check rubber posts that hold idle control valve (2)
check / replace oil tube o-rings
inspect engine mounts
camshaft housing gaskets
upper "cooling socket" gasket

EDIT:
check balance shafts/cam shaft "spacer sleeves", they may have deep grooves from old seals.

EDIT: do you have PET parts catalog? If not, download it from HERE.

Phew, I got my hands full, probably wait until after summer for it can cool down here in so cal.

Thank you for the info, going to start seeing what I need to have the parts ready

[Monkey Wrench]

hold your horses just a sec - )
it might be a stuck open fuel injector,
if so it can drain the normally stored pressure of the fuel rail into a bore and
that will also produce a bunch of white smoke on startup. probably followed by somewhat normal operation.

if its a head gasket, you wmay see froth it he oil, or water dripping from the tailpipe or the sweet smell of antifreeze, other symptoms are that the water level decreases if it's blowing out the coolant and you may see weird stuff happening because the leak can cause water pressure and then fill and empty the water bottle. if water sprays it into the bore it may make one plug look extra clean. it's getting basically steam cleaned.

you dont want to pull the head off because of a misdiagnosed and stuck open fuel injector ! if its that, you can smile because it's a lot cheaper and easier.


look at the plugs if one is fuel soaked If so, the fuel rail out and see if it can shut off the flow of fuel. you'll want new o rings and wet them with oil to get the fuel rail back in. the injectors wont fire with the grounds unhooked so ground them if you remove grounds.



be careful and take all the necessary fire precautions i found the issue in a volvo by this and then I could see that if I turned the key (momentarily only) than ran around to see how they all sprayed, ( a cloth under each injector) one didn't shut off and was pissing fuel after Key off.. dont crank it for more than a moment or you are just spilling fuel.

please be careful don't spray fuel around inside your shop and make sure you have a fuel rated extinguisher ready and in hand. fuel fires are really bad. had a buddy drained his gas to a bucket, and then tripped on his trouble light, his face was all deformed and it was extremely traumatic. so be careful !

if you like you can have injectors serviced. if you have a fuel pressure guage you can do the leak down test that's a more polite way.

check on Clark's garage. there is a recommended procedure that doesn't; involve pulling the fuel rail or sraying fuel about.

if an injector is stuck open it can't retain fuel pressure. way too much fuel makes white smoke too, for the first block or two. that's what I saw in my volvo 740. I noted the plugs looked not bad, next I checked again and the problem bore's sparkplug was totally black with soot, so the plug may vary quite quickly. maybe even look normal as it cleans itself once it starts firing.. some may depend on momentary conditions.

head gasket can leak from the bore into the exaust, it can also leak from water to oil, it can do that because of an oil cooler issue.

I think most gasket failures are from waterjacket to the cylinder and out the tailpipe but It perhaps can also can fail a bit differently .

check your oil for water and your water for oil , look for a frothy filler cap.

i've heard a bad head-gasket can be sensed with a co meter , normally there is no exhaust in the water bottle and the meter can detect exhaust in the water bottle. I dont own one.

often the first sign of a headgasket failure is the need to add water, but no visable leaks.

if you drive watch you temps a head gasket fail can cause it to overheat suddenly
a little puff and a drip well ok . but when the head runs dry, and that can warp stuff. i've seen gasket failures happen a couple times in my volvos, no warping, but they are much tougher cast iron engines. the 944 is aluminum. if I had to drive it far Id pack lots of water with me stop every few blocks and make sure its still full and with an eye on the temp guage

if you dont overheat it you won't warp it. if you need to. just wait let it cool and continue. - to save a tow.

it may be possible to get water or fuel into a bore to such an extent it cant; compress. Water will not compress like air, and that hydraulic lock can possibly blow a hole in the side of the bore ofr do something equally not funny.

perhaps unlikely during operation but if it sits, a bore might get filled up, if its been sitting in this state you can remove the plugs and give it a spin to clear the bores and check for this rather than blowing it up.

I tried the magic fix in a bottle on an older car, then when it didt work I took it apart, I could see how it was trying to work. its a weak solution at best, I had no success and there are different types. i used the strongest type and it requires removing the water a few times

it doesn't mix with coolant. some you jut add to the coolant, and hope. these may get a guy to a mechanic is he was out of town and had an issue, that wasn't left to get real bad.

i do not think the magic fixes in a bottle are much help otherwise.

maybe if the bottle has a pretty genie in it she can close her eyes and give it a nod and a wig ;-) I keep trying to do that, never worked yet ;-)

[wwdwgs]

MW, to find a nice genie, you must have a right bottle.

[Monkey Wrench]

maybe , I've heard Tequila works ;-)

[Jfrahm]

Crank it cold for a few seconds, then pull all the spark plugs and look at them.
Any wet with coolant?
Any wet with fuel? [fuel smells like fuel, fuel burns, coolant feels greasy and smells sweet]
Any suspiciously steam cleaned?

[Monkey Wrench]

if you are doing that and do own or can access a compression guage, try to get the readings. the pressure of each individual cylinder should be somewhat equal, if the readings are really low in any one cylinder it might indicate a valve not sealing. as a second step you can squirt about a capful of oil into each bore and then recheck the compression readings. write all 4 down again so you can compare,

if you see a difference , it generally means the rings are not sealing well and the oil is helping (very temporarily) the oil wont do anything to seal a leaky or possibly burned valve. Id say an exhaust valve is probably a lot more susceptible as it is exposed to the hot gasses while open on the exhaust stroke.

the gauge probably is not a very a large cost. if any cylinder is extremely low it means you'll at least need to pull the head to fix that aside from the gasket issue. if not new rings too. good info to know. worth the price of a compression gauge, wont take long to do. it may be interesting to compare compression readings with others with comparably old engines.

just a wild guess and a stab in the dark but I'd say if it were in good condition you might have an even 200 PSI across all 4, a worn engine may still be serviceable at 150 PSI but at that stage it probably has some degree of blow by, if any are down to 100 or below I'd suspect trouble.
Acceptable readings that aren't simply my opinion or a guess are likely available. it'll be documented. these numbers are only mere guesses.

another test you can consider is to connect your air compressor to where the spark plug screws in, I made my own just by knocking apart a spark plug and stuffing a tubeless tire valve in there , but you can buy one if you prefer. the piston will try to descend as you pressurize it unless it is exactly at TDC. the idea here is you do it with both valves closed, piston at TDC so valves are closed.

the simple way to find that position is just turn the engine put your thumb or wadded up wet paper towel to block the plug hole, turn engine in its normal rotation until you feel the compression sense the "wind" or until your wadded up paper towel pops out, beyond that you can feel with a drinking straw to sense the piston at TDC or look at the crankshaft marking. when the cylinder it at TDC on its firing position this happens right after it finishes the compression stroke. the compression stroke is the stroke where you feel "wind"
with the valves closed and the piston at TDC you can try to compress the air in there with the tool, if you have a leaking valve or bad ring then the air will be escaping, it should be able to retain some pressure for a while , how quickly it leaks down gives you a sense of how well its sealing.

I guess you can use the flywheel lock if you want to remove the starter and have one. Just be aware that if the Piston is not exactly at TDC and you compress it, or if you turn the engine , the compression can turn the engine in either direction to BDC quite forcibly so dont be surprised if this happens. if you had a badly burned valve the cylinder would not be able to retain pressure and you will hear the airflow. this wont fix anything but it helps when making the decision to pull things apart, or if its generally ok. its good to kow the compression numbers before taking a head off, you can recheck it after and see a measurable difference if you do the valves.

you cna check all 4 and to prevent unnecessarily engine turning, follow the firing order. a half a turn of the crank will be the next one and so on. two turns and you are back where you started.

if for example one cylinder won't seal because of a burned exhaust valve or a broken piston then its at that point obvious you need a head gasket and to pull the head for a closer look and at that point you'll decide if you are going to fix just the head and valves or also work on the bottom end.
if you need to move forward and pull the engine. You then want it raised with enough clearance to get the engine out from under the hood area, Id consider the logistics of that before you pull a head, otherwise you maybe faced with moving the car about with no engine to push it should you find it's necessary.
if your findings are generally acceptable , then when you do the head gasket for the water leak issue , it will help make the decision as to weather to work on the head or just change the gasket.

if the head is off then its not necessarily easy to tell if you have a broken compression ring or similar, you can look at the marks on the bore you can try to wiggle pistons and inspect, you can measure the bores for out of round, maybe get some indications about bottom end wear visually, You
cannot check compression once the head is off though. i'd do that prior so you have that info.

last time I did a compression check I found my battery got a bit weak after the frrst couple. It affected cranking speed, thus my readings. you really want the same cranking speed for the results to be compared. to crank the motor you can jump the battery to starter motor connection or use a helper to turn the key. just charge up the battery and if it slows due to the drain of the test, charge it again between each check.


Next thought is if you are rebuilding that engine, will you need to move the car out of the shop or is there room to work on that?

Anticipate the worst and hope for the best ;-)

some of this can be accomplished by a determined back yard shade tree mechanic, not everyone is up for that degree of wrenching and many will pass it to a real mechanic.. It presents questions on the timeline too and cost. You can ask yourself all that.