[TheOdessa]

So I want to get the car compression tested and/or leak down tested because the other day I noticed what I think was white smoke coming from the exhaust. I am going to take it to a shop to get it done because of time constraints in my schedule with work and home. Should I get a compression test then a leak down if needed, or should I just do the leak down since I am getting it done at a shop?

From what I understand, SOP is you do a compression test first and if it fails, leak down to pinpoint; however, I'm thinking if I ask for just a leak down test it'll pinpoint a problem if there is one and that way I won't have to pay for two tests if needed. Thoughts?

[Cabikejumper]

Couldn't white smoke just be from condensation from sitting over night?


If it were me I would just do a leak down test of your short on time. Shops here charge 10.00 for a leak down.

[bulloch27]

Let's just say that there is a problem inside your motor... are you going to rebuild it or replace it? If the answers are no, there is no need for either test. The only things compression checks and leak down tests tell you is that you have either an individual cylinder problem (broken/worn rings and/or bent valves) and help you pin point blown header gaskets. I'm not saying don't do it but you'd probably come out better just buying your own compression test kit or leakdown test kit. Either kit will be available for about the same price as you're going to pay someone else to check it. If you have no intentions of tearing into the motor if it needs it, save the money and don't worry about it. A little smoke on start up is not terribly uncommon of a higher mileage motor and is typically indicitave of worn/leaking valve guide seals (which have nothing to do with a compression test) and are fairly easily replaced if you have a little tech skill. Smoke while running/accelerating is typically indicitive of worn rings. These motors will take a load of abuse and run several hundred thousands of miles so I wouldn't be terribly worried unless it smokes like a locomotive.

[Eagle2000GT]

Are you basing your judgement on a single incident or is the white smoke a regular thing? The weather is getting cooler. White smoke is usually condensation. Does it stop smoking after your exhaust system is completely warmed up? You're in Florida but up here we get condensation so bad that water sometimes drips from the tail pipes.

[TheOdessa]

bulloch27- I do not intend on tearing into or replacing the motor - but it's be an option if I had to. I am just curious as to what could have caused it, and if it something easier to replace such as valve guide seals, I'd rather do that then let it go. My motor is ~11 years old with 75k miles so I was expecting some kind of problem.

Eagle- it happened even after the car warmed up so I ruled out condensation as that usually only happens when cold. It actually happened at a stop light on the way to work when I revved my engine slightly.

[bulloch27]

If its smoking while running, not just on initial start up, it's most likely not valve stem seals. 11 years old and 75K miles is not much in my opinion, mine is 8 years old with 125k and doesn't smoke a lick. I also have one that is 6 years old with 120k that doesn't smoke and have had several. If you have no intention of tearing into it I wouldn't worry about it too much. Keep a good check on oil consumption and when it gets to a point that it's too far gone, replace the motor or rebuild it. A compression check won't tell you how it happened, only that it did happen.

[TheOdessa]

Well thank you very much sir. Only because I am curious, off the top of your head, what do you think it may be?

[bulloch27]

Nothing but two wild ass guesses since i'm not looking at the car. Excessively worn rings (variety of reasons) or just simple condensation due to the greatly varying weather conditions this time of year(varies by 30+ degrees daily here in Ga).

[TheOdessa]

While the variations aren't as drastic down here in Tampa, Florida, the temps have been bouncing around a lot. The only reason I ruled out the condensation is because it happened while driving to work- a good 5 miles into my drive so the car was at normal operating temp.

Assuming your wild ass was correct, a compression test would reveal this, yes? Since we have a long weekend coming up, I am now thinking about just doing the test myself.

Another route I was thinking of was data logging via my SCT tuner. Would that turn up the same and/or more accurate results?

[bulloch27]

Datalogging wont tell u anything in regards to compression or oiling. Checking the compression will let you know if you're cylinder pressures are where they need to be and identify potential problem cylinders but won't identify exactly what the problem is. if you have unequal pressures on a cylinder it typically indicates a ring and/or valve issue. Low compression on two or more adjacent cylinders indicates a blown/damaged head gasket.


Didn't you have some intake problems a while back? If so, are you certain that you aren't leaking coolant into the intake ports?

[TheOdessa]

Ah, I see. When I bought the car, the previous owner did not get the upper intake swapped out as it was the plastic crossover. I replaced it out with a Ford Racing Unit. I've been trying to figure out what is causing my car to idle weird and cause the car to shake left and right a bit, but I have a feeling that is a loose engine mount or off-balance balancer.

If I do a compression test, would I look down the spark plug hole once removed to see if there is coolant build up at all to test for coolant leaks?

[mwilly]

Are you sure it's not blue smoke? I had valve stem seal issues with my car and the engine only had 50k on the clock. I had the same problem, let the car idle for a bit, then blip the gas and a puff of blue smoke comes out the exhaust. Something to keep in mind...

Turns out the guy who had the car before me put Fel-pro valve stem seals in the heads, and they leaked like a bastard. If you find out it's valve stem seals, get the Ford ones, they're worth the price.

[TheOdessa]

Thanks for the input mwilly! How did you find out that was your problem? Steps that you took? Ill try the idle and blip test!

Did it also throw your idle off a bit? The needle doesn't move at all and it stays at a constant RPM when idling, but the car just has a little shake to it.

[bulloch27]

I'm not saying it's not valve stem seals but you have to understand the operation of an engine to understand what I'm saying. Typically leaking valve stem seals on intitial start up. As oil puddles around the vavle stem while NOT RUNNING it accumulates and runs down the valve stem past the failing/leaking seal. At start up you will see a puff of smoke as the accumulated oil burns off. Unless the seals are ripped in half you should see no visible smoke during running. Keep in mind that is the TYPICAL scenario and there can be exceptions. Typically oil smoke during running is from excessive ring wear.

You say the enigne is shaking around, which means to me a misfire. Misfire can be caused by a variety of things but since we're talking about the possibility of a coolant leak here lets talk about that. If the intake gasket is leaking and allowing coolant/water mix to enter the intake ports of the heads you're not going to see any external coolant leaks (at least not related to the misfire). Antifreeze and water do not like to burn and can stop proper combustion in the cylinder AND will produce white smoke. I'm not saying that any of these are actually happening to you, but these are all very strong possibilities and it's very difficult to diagnose a car's problems over the internet without putting hands on one.

My initial question of are you going to fix it is one I ask everyone who is getting ready to incur a large shop bill. When someone tells you its gonna cost you $400 to diagnose a problem that is then going to require a $1500 fix..... think about it hard. Are you going to fix the problem for a $1900 investment? If my motor is burning oil and i'm confronted with an estimate in that ball park i'm going to find a junkyard motor for $1200-$1500 and replace it.

[mwilly]

I ended up doing a compression and leakdown test to rule out the rings and other mechanical problems. It didn't seem to affect (or effect) the way it ran, just poof of smoke after idling a while or on initial startup. They were aftermarket seals, so that's why they were leaking. Most of the time when they leak, they are on cars with very high mileage. As far as the engine shaking a bit, I thought it was normal...It wasn't causing a misfire or anything like that. Also, there was no oil in the catch-can I made for the excessive blowby I thought I had. That's how I knew it wasn't the rings.

I agree with everything Bulloch is saying. You need to rule out the obvious, so go by process of elimination. It's very difficult to properly diag. a car without looking at it and seeing the whole picture.

[mwilly]

Just read about your coolant leak. Intake gaskets will also cause the problem you describe. Did you use new gaskets when you replaced the intake?

[TheOdessa]

Originally Posted by bulloch27 I'm not saying it's not valve stem seals but you have to understand the operation of an engine to understand what I'm saying. Typically leaking valve stem seals on intitial start up. As oil puddles around the vavle stem while NOT RUNNING it accumulates and runs down the valve stem past the failing/leaking seal. At start up you will see a puff of smoke as the accumulated oil burns off. Unless the seals are ripped in half you should see no visible smoke during running. Keep in mind that is the TYPICAL scenario and there can be exceptions. Typically oil smoke during running is from excessive ring wear. You say the enigne is shaking around, which means to me a misfire. Misfire can be caused by a variety of things but since we're talking about the possibility of a coolant leak here lets talk about that. If the intake gasket is leaking and allowing coolant/water mix to enter the intake ports of the heads you're not going to see any external coolant leaks (at least not related to the misfire). Antifreeze and water do not like to burn and can stop proper combustion in the cylinder AND will produce white smoke. I'm not saying that any of these are actually happening to you, but these are all very strong possibilities and it's very difficult to diagnose a car's problems over the internet without putting hands on one. My initial question of are you going to fix it is one I ask everyone who is getting ready to incur a large shop bill. When someone tells you its gonna cost you $400 to diagnose a problem that is then going to require a $1500 fix..... think about it hard. Are you going to fix the problem for a $1900 investment? If my motor is burning oil and i'm confronted with an estimate in that ball park i'm going to find a junkyard motor for $1200-$1500 and replace it.

As always, I do appreciate your insight on this. Sounds like I just need to take it step by step. I am thinking about taking it to a shop on Saturday just to get basic tests done by a trusted mechanic. Compression and leak down. Talk about a pain but I guess that's what happens when you buy an older car. I appreciate all your insight, and will report back when I get it looked at. I was thinking it might be a misfire which is why I changed out the plugs to stock Motorcrafts, put on new COP's and boots, and Sea Foamed it. Also replaced the injectors with cleaned and reflowed as well as new fuel filter. The engine doesn't shake violently, but you can feel it shake a tiny little bit left to right every...2-3 seconds maybe. Would a misfire throw a code though? Im guessing a coolant leak could cause a misfire since I replaced everything else I could think of.

MWilly- thank you as well. I appreciate your input and it's helping a lot on this.

[bulloch27]

A little shake is normal... it's not a four cylinder Sentra lol. Misfires can but rarely throw a check engine light or code unless its severe. If your mechanic has the abilitly to run a cylinder contribution test on his computer I would suggest it. It allows you to view the real time data on each cylinders' spark so you can see the misfire as it happens (which is typically very mild and hard to find without the contribution test). Keep us posted.

[TheOdessa]

Lol I hear you, but it's not a normal shake. It's on and off

I told them about my problem. My mechanic is going to

Pressure test the cooling system
Compression test
Leak Down if needed
cylinder contribution test if needed

I'll update on Friday. I'm taking it in that morning

[TheOdessa]

So I just got back from the shop. I told them about my concerns (slight shake left to right on idle + smoke from tailpipe). Mechanic got me and brought me into the bay. He said the slight shake is normal on these V8 mustangs due to the cam they use. They work on a lot of police interceptors and they do the same thing - pretty much nature of the beast? I told him I guess I just wasn't used to this car, or V8's in general for that matter and was expecting a silky smooth idle. The coolant was at the right level showing there is no loss. Maybe I am just being too picky?

They then hooked it up to their fancy computer machine. They found nothing except a misfire on cyl 6 far in the far past, but apparently I fixed whatever it was when I did the COP/spark plug replacement because it wasn't recent at all. I asked him about a compression test, but he said he didn't feel the need to do that because everything was within spec when running it on the computer. On one hand, I would think he'd want to do it because it's more money for the shop, but if he honestly thought there was nothing wrong it's good he didn't make me do something I don't "need"?

My question is if everything is within spec and he saw nothing wrong on the computer, should I worry at all about a compression test or any further testing at this point? He charged me nothing, nada, so it's not like I was out of pocket on any of this. Let me know. Thanks!