Loud cracking noise

[Inferno_Rob]

As I was driving the car home last night and I got to about three blocks from home the engine started making a loud cracking sound as if it was eating a rod or valve. The power was down and oil pressure was very low.
I have taken great care of this car but now I suspect since my last oil change that the place I took it to for an oil change may have done me a huge disfavor.
When i got the car it used standard 10-30 wt oil and ran on it fine. When I took it in two weeks ago to the shop they told me according to their computer it should be on Synthetic 5w30.
It cost more to use and they told me it is recommended.
Now I have an engine I think is junked. Would the synthetic oil do this?
I drive an 83 944 in great shape and now it sits till I test it's compression.

[Gremlin85]

Oh god... I would always recommend doing your own oil change. These cars came out the factory very happy on 20W50. The lighter oil is not good in these cars (some may say different). I use 20W50 in the summer and 10W40 in the winter and it runs strong with perfect oil pressure (hot and idle 3 bar to about 3.75 bar).

Where is your oil pressure at?

The thinner oil would not provide adequate pressure and it sounds to me that the bearings are not happy and your valves might be clacking away from no lubrication (your hydraulic lifters might also not be pumping up correctly which would effect performance).

CHANGE THAT OIL... thick... its cold in canada so use the 10W40 first and use a Mahl filter or a Porsche filter.

I'd go back to them and give them a piece of my mind... if I were you.

They were just trying to make a buck off ya... where did you go anyway?

::EDIT::

Before you put anything in, get those compression numbers to be sure things are OK. If those seem fine for the age and mileage, then do the oil swap. Get back to that place you went either way... there are bones to be picked.

[Eldorado]

I run 10W30 synthetic in my car year 'round, with the porsche filter... noticed after my first change to synthetic that my lifters started to clack... threw a can of wynn's engine treatment in there and it cleared it up after a couple hundred miles..

[Rick V]

The PO of mine was running 5w30 in the car and the cam followers sounded like clacking crap. When I rebuilt the head I converted it to 20w50. Alls been quiet since.

[toolboy62]

I agree with the other comments, I'm not sure what is wrong with your car, but most German cars of that vintage are happiest with an xW40 or xW50 oil. Also 944s are known for being hard on the rod bearings.

nate

[Eldorado]

actually.. rod bearings makes sense... I think...
although I'm not 100% sure they give an audible "warning" before they're completely toasted..

[EMBPilot]

u guys think i should change from 5w30 a w40 or w50???

i bought my car the PO said the PO he got it from always used that oil, and that was probably the guy that dropped the rebuilt motor in.

what do you guys think?

my oil pressure runs right on schedule per clarks garage.

[Eldorado]

If it works, Kevin - then it works!

[toolboy62]

Ayup, my thought is, if you are happy with the oil pressure with the 5W30 and there's no bad noises from the engine, it's probably OK. However, at ~130K miles, *my* '44 definitely prefers 5W40.

I don't buy into the "heavier is always better" theory of selecting oil; I'd actually use the lightest weight the engine seems to be happy with. However, I've had several VWs and now this 944, and with all of them I could tell almost immediately if someone had used 10W30 in it because as soon as it got hot the lifters would clatter at idle, which didn't give me the warm fuzzies.

nate

[Techno Duck]

I would personally run 10w40 at the least for general street use (i mean 90 degree summer days). I think 10w30 is much to thin in the summer, winter is no big deal.

I would be even more inclined to run 10w50 in the summer, but that is only available in M1 (or synthetic in general) i think.

If you do hard driving (auto-x, DE) i would defenetley not run anything less than w50. Running hard for 60 seconds, then sitting in staging for 5 minutes and repeating that four or five times before you shut your car off leads to super high oil temps, especially in the dead of summer with 90 degree ambient temp. Ive seen as high as 240*F on my car with the oil pressure at about 2 bar with 20w50. I would of probably had around 1 bar (if that) running anything less.

The other advantage of heavier oils is they will reduce your oil consumption somewhat. But again, that really only comes into play if you drive your car real hard.

[Inferno_Rob]

I took it to a Mr Lube. The car was fine for the first couple of weeks and the oil pressure was fine. I have run a couple of tanks of fuel thru it now and last night it went south. It starts up fine and runs but it makes a loud racket as if it was a rod bearing or exhaust valve slapping. It will get louder with rpm and almost went away at idle. I keep running time to a minimum to get an idea of what it is.
The oil level is right up there but the pressure is 1bar from last drive and oil light flickered on and off a few times.
There appears to be no tell take signs in the oil (its clean still) the exhaust smells fine and appears normal, the power seems down from my last drive in it. I will check compression ASAP and get a better idea if it is lifter, valve sticking or rod bearing.
At least I can feel safe that the Synthetic oil is ok for my engine and this place didn't put something in that will ruin it.

[Gremlin85]

It spun a rod bearing. I hate being the bearer of bad news....

My ASSuption would be... oil too thin, 944 engine being heavy on rod bearings as is, now made worse... rod bearing spins... our bearing...




(incase no one caught that last bit... JAWS) a little humor helps...???

[Techno Duck]

Good oil pressure at startup (cold engine) but 'clack clack' means a sticking lifter. Low oil pressure at startup and you more than likely have a rod bearing problem. Stop driving the car now so you dont destroy the crank shaft. Drain the oil and see what comes out.

[WizPorsche944]

I Use Mobil 1 15W50 all year

[Razorback1980]

Read the data sheets on oils and there is a lot of information that you can quickly learn about each of the oil brands and some of the qualities. Castrol sponsored my race cars for years, so hanging around oil engineers, I can repeat what Pete has told me.

There are really six different properties for oil that you should pay attention to...viscosity, viscosity index, flash point, pour point, % sulfated ash, and % zinc.

Viscosity is the measure of how well an oil flows...I bet each of you knew that didn't you? Actually it's the property of an oil to develop and maintain a shearing stress dependent on flow and then to offer continued resistance to flow. Thicker oils generally have a higher viscosity and thinner oils a lower. The shear stress is what provides lubrication for the engine. Too thick an oil and the film will not form evenly if it gets in the gaps at all...also too thick an oil film and it will tear at high rpms....too thin and the shear stress of the film will be so low that the bearings and their shafts will rub on the high places. These numbers are derived by measuring the oil flow at specific temperatures. The low number is the viscosity of the oil at 0 F. The W tells you that the oil meets certain specs at 0 and therefore approved for use at lower temperatures.

Multi-viscosity oils are engineered to work the opposite of normal fluids with the exception of water. Oil companies add polymers to the oil to get them to be thinner at cold temperatures and thicker at higher temperatures. That sounds like a very good thing but there are draw backs to having those properties. The wider the range of the lower and upper number, the more polymers they have to add to the oil. Polymers are great to changing the flow of the oil but have no lubricating properties to them. In other words 20W50 oil is 20 weight oil that will not thin more than 50 weight when hot. While adding those polymers was one of the best things to happen to oil, it's best to choose wisely and use them to your best advantage. In other words ALWAYS choose the oil with the narrowest span of vicosity numbers that will operate in the temperatures you think your car will be in. Lubrication isn't the only problem associated with having all those polymers. The higher the polymer, the higher the sludge deposits and increased problems such as collapsed lifters and sticky rings. Bottom line is fewer polymers = better performing engine with less oil related problems. Basically a 10W40 oil has less lubricating efficiencies than a straight 30W oil. In fact, most manufactures will void warranties if you use a 10W40 oil any more. With that said, I run a 20W50 oil in my car which has the same point spread that a 10W40 oil does, but there is one major difference...it starts with a heavier base so it requires less polymers to provide the change in viscosity...because it has less polymers and more oil to form the film, it lubricates better and is not as subject to viscosity and thermal breakdown. Oils such as Mobil 1 5W30 oil have no viscosity improvers in their oil which is why it works so well and so many auto manufacturers use that oil. Certain weights of AMSOil also use no polymers as I'm sure there are a few other manufacturers have oils blended like that but I'm unsure what they all are.

Viscosity index is the rate of change an oil changes viscosity within a temperature range. This number describes the amount of lubrication and is what keeps bearings lubricated.

Flash points are another indicator of how good an oil is. Flash points are the temps that oil gives off a vapor that can be ignited. The lower the flash point, the more it will burn off cylinder walls which run at a very high temperature. If it burns off, there is no lubrication. The higher the flash point, the better the oil and the higher the grade of crude oil used to manufacture the oil.

Pour Point is a number of very high importance although it's seldom looked at. Pour point is the lowest temperature that an oil will pump and maintain adequate oil pressure. It's derived by measuring the temperature that a chilled oil shows no signs of movement on a slanted surface plus 5 degrees.

% sulfated ash. This measurement is the amount of deposits left behind after oil burns. The lower the sulfated ash, the less deposits you will have in your engine.

% zinc. This is the amount of zinc added to the oil as an extreme pressure additive. Under normal operations, zinc doesn't really do much for an engine. It only helps when an actual metal part rubs on another metal part. The zinc reacts with the metal to prevent wear and damage. Zinc is especially useful in a high revving or turbo engine. The zinc doesn't give more protection, it provides a longer protection. Of course with it being an additive, it will also lead to more deposits and other engine problems.

[EMBPilot]

wow, good thread.
im really starting to get the feeling i should switch from 5w30 to at LEAST 10w40 ... yikes....

[magickingdom]

So Razorback, after all that, what oil do You recommend?
Brand and Viscosity?
Synthetic or regular?

[Gremlin85]

+1^ Great information Razorback.

[Wipeout]

Hrm, maybe I'll be switching from 10w30 at my next oil change to something like 10w40 or more. Did I miss this memo on Clark's when I did my oil in December?

[Razorback1980]

One thing I forgot to mention in all that is synthetic vs nonsynthetic. Synthetics are a little different. The rules I follow are this.

If I am using a nonsynthetic, I never put a 5W or 10W anything in my car. Here is the reason why. To get a 5W or 10W oil, you have to start with a lesser quality oil and add polymers to thicken it. Since polymers do not lubricate, you want an oil with less polymers. I also use oil with the smallest difference between the first number and the second. To get the larger gaps, they have to add more polymers and I want a minimum of those because not only do they not lubricate, but they also break down and leave sludge in your engine. I do use 20W50 in cars and I know what you are thinking 20W50 has the same gap as 10W40 (which I don't use). The difference is that 20W50 starts out with a 20 weight oil instead of a 10 weight. If I need a thinner oil for cold weather in a nonsynthetic oil, I use straight 20 or 30 weight. With my new cars which call for 5wsomething, I use synthetic oil because they don't start with a poor quality of lubricant to engineer that oil.

So...long story short here is what I do in Texas....I run standard 40 weight in the winter and 20W50 in the summer. If I lived further north, I would run 20 or 30 weight in the winter and 20W50 in the summer. If I wanted to run synthetic, then I would do 10W40 in winter and 20W50 in the summer.

The three oils that are exceptions (that I know of but there are probably more) to the rules are Mobil1, Castrol GTX, and AMSOil, they get multiviscosity oil without the polymers which is why Kevin hasn't had any problems running Mobil 1 and why so many high performance car companies recommend Mobil 1.