confusing compression and leakdown test results

[Chicken Patty]

Not everyone deserves a DSM. Your car should have been in your hands a lot earlier.

 

[rlacasse1]

Not everyone deserves a DSM. Your car should have been in your hands a lot earlier.

Yeah no kidding. I don't know what the person was thinking?

I'm just really hoping that there is no valve damage.

 

[Chicken Patty]

Yeah no kidding. I don't know what the person was thinking?

I'm just really hoping that there is no valve damage.

I'm hoping for the same bro, keep us posted and best of luck.

 

[rlacasse1]

Well, I got it going. Put on a new timing belt and a new balance shaft belt. I noticed an immediate difference just from the start up. It is much much louder when it is running now.

I'll post up some warm compression results tomorrow.

I found all the parts I needed off a 95 Hyundai Sonata. I didn't realize they came with a 4G63 at first. I was actually just looking for a g4cs in the hyundais and happened across a familiar valve cover. So i got to looking and it all looked the same. So that's where I got my crank sprocket and back plate from.

 

[Chicken Patty]

Well, I got it going. Put on a new timing belt and a new balance shaft belt. I noticed an immediate difference just from the start up. It is much much louder when it is running now.

I'll post up some warm compression results tomorrow.

I found all the parts I needed off a 95 Hyundai Sonata. I didn't realize they came with a 4G63 at first. I was actually just looking for a g4cs in the hyundais and happened across a familiar valve cover. So i got to looking and it all looked the same. So that's where I got my crank sprocket and back plate from.

Yep, they share a lot of parts Glad it's running fine bro

 

[rlacasse1]

Well, I'm not positive that is running correctly just yet. I think it's doing better. But I don't know if it's just right. I noticed it got a lot louder and seems a little more responsive when I just rev it in neutral. I will try to get warm compression test results posted tomorrow.

I knew the older hyundais had the g4cs, but I didn't realize that the newer model Sonatas still came with a 4g63. I think I may go get its valve cover though because it looked good. I like their design better.

 

[Chicken Patty]

Well, I'm not positive that is running correctly just yet. I think it's doing better. But I don't know if it's just right. I noticed it got a lot louder and seems a little more responsive when I just rev it in neutral. I will try to get warm compression test results posted tomorrow.

I knew the older hyundais had the g4cs, but I didn't realize that the newer model Sonatas still came with a 4g63. I think I may go get its valve cover though because it looked good. I like their design better.

Yep, I like their valve cover better. I will get one eventually.

Well, as far as your car, I'm hoping for the best dude, get that compression test done, let's see how it's doing.

 

[Calan]

Any updates? I'm curious as to how your comp/leak-down test results after getting the timing issue resolved.

 

[Boostinsideways]

Warm engine for a compression test is a must. When I was looking to get the current dsm I was told it had a blown headgasket, when I did the compression test cold I got 105,135,135,110.

I called the local mitsu expert to ask him about compression numbers for a 2g, he said that rings were shot unless I didnt warm it up first.

So, I warmed it up to full operating temp, 140,175,180,145. When I got the head off, you could tell it was leaking compression really badly at both ends of the head, and worse on 1st piston end than 4th piston end of the engine.

 

[rlacasse1]

Any updates? I'm curious as to how your comp/leak-down test results after getting the timing issue resolved.

No, update yet. I haven't had the time to do a warm compression test. I will try to get it done tonight. I have just been really busy between being in the military and trying to take classes as well.

But, it does run a little bit better. But not perfect just yet, I still have to work out its idle issues. Also, I'm guess it may have a little valve damage from the ridiculous timing job it had.

I'm a little scared to pull spark plugs while the engine is hot because I have had the threads come out on the plugs before. Made for a bad day.

But I will try to get a warm test tonight.

 

[Chicken Patty]

No, update yet. I haven't had the time to do a warm compression test. I will try to get it done tonight. I have just been really busy between being in the military and trying to take classes as well.

But, it does run a little bit better. But not perfect just yet, I still have to work out its idle issues. Also, I'm guess it may have a little valve damage from the ridiculous timing job it had.

I'm a little scared to pull spark plugs while the engine is hot because I have had the threads come out on the plugs before. Made for a bad day.

But I will try to get a warm test tonight.

That don't happen often at all dude, just go for it when you have a chance.

 

[DSM_munky_man]

Just a note to add about the compressions test. I dont know if you know this or are doing it, but when you do it take all the plugs out. That way the motor spins easy, and the starter doesnt fry from cranking it many times with compression. plugs out takes away compression from the other 3 cylinders and makes it easier on the starter and it will be happier.

 

[bertrenolds]

A wet compression test doesn't work well on these cars, the oil just fills up the piston dish, and raises compression no matter what. The leakdown test is a better indicator than a compression test anyway.

And you will create an explosion in your cylinders when you start the car.

As I understand it a leakdown test is really the only way to test everything correctly. A compression test is not always accurate.

 

[Chicken Patty]

And you will create an explosion in your cylinders when you start the car.

As I understand it a leakdown test is really the only way to test everything correctly. A compression test is not always accurate.

A compression test can and usually tells you a lot, probably enough to know what's going on. A leakdown test can further narrow down your issue.

 

[rlacasse1]

Alright. I just finished a warm compression test. There was no change to the compression numbers. So at this point I'm going to go ahead and put a new headgssket on it. I hope to god that's where its losing compression. That would also explain it pushing coolant when its hot. hopefully it will fix it.

 

[Chicken Patty]

Alright. I just finished a warm compression test. There was no change to the compression numbers. So at this point I'm going to go ahead and put a new headgssket on it. I hope to god that's where its losing compression. That would also explain it pushing coolant when its hot. hopefully it will fix it.

Best of luck bro, try to put some ARP studs while at it if it doesn't already have.

 

[Calan]

I hope to god that's where its losing compression. That would also explain it pushing coolant when its hot. hopefully it will fix it.

Do a leak down test and you'll know for sure before you even open it up.

 

[rlacasse1]

I already did a leak down test. And that is what's confusing me. The compression vs leak down results. I'm getting low compression. But when I do a leak down I get no leakage. No air passing into the coolant, and little to no air entering the crankcase. The leak down tester shows that it's fine.

 

[rlacasse1]

Ok. So before I started tearing this engine down I decided to find out what my CEL I had showing was for. Turns out its throwing a code for my knock sensor. Felt the knock sensor and it has the gooey shut coming out the back. So I know its bad and I'm going to assume that's what's killing the power since the timing is being retarded so much and causing it to only boost to 5 lbs.

My main question is can it cause the exhaust manifold to get extremely hot since the combustion is happening later and closer to when the exhaust valves are opening? Will it cause that?

 

[Calan]

My main question is can it cause the exhaust manifold to get extremely hot since the combustion is happening later and closer to when the exhaust valves are opening? Will it cause that?

If it's truly knocking that much, sure. It could be because it's either too rich or too lean (most dangerous), both of which will affect EGT's.

The pulled timing due to the knock will also increase the EGT's.

 

[rlacasse1]

Oh, and can it cause enough fuel to not burn in the cylinders, from lack of time for the gas to burn, to where it will wash out the cylinders and cause the compression issues I have.

 

[Calan]

Oh, and can it cause enough fuel to not burn in the cylinders, from lack of time for the gas to burn, to where it will wash out the cylinders and cause the compression issues I have.

If you were running super rich. But you would be blowing a lot of black smoke if that's the case...definitely enough to be noticeable.

It takes quite a bit of fuel to wash the cylinders at higher loads and RPMs, due to the expansion from heat and much higher cylinder pressures. It is usually more of an issue at idle and very low engine loads/RPMs.

One thing to remember about a compression test vs a leak-down test: with a compression test you are generating cylinder pressures of 150+ psi. With most leak-down tests you rarely go over 50-75psi, if that. So you could have a problem that only shows up when the cylinder pressure is high enough, and at the lower pressures of the leak-down test everything looks good. It doesn't happen often, but it is possible.

Make sure the crank can't rotate and all of your hoses/connections are good...and inject as much pressure into each cylinder as you safely can and see if the results change. You may want to bypass the leak-down tester though, as some of them don't hold up well at input pressures above 80psi or more.

FWIW - I found a small HG leak this way. My car seemed to be pushing some coolant and the compression test wasn't great, but not horrible; #1 was down 10-12psi or so. Everything looked good on the LDT until I cranked up the pressure, at which point I found that I was leaking compression into the coolant. I would see a few bubbles at the water neck about every 10-12 seconds or so. It was taking that long for 100psi of injected air to build up enough pressure to push past the leak point. Once it did, the cycle would start over again, and about 12 seconds later... a few more little bubbles would appear.

 

[rlacasse1]

My leakdown tests were done at 100 psi.

And I haven't had the car to high rpm. All my warm UPS the car was just idling. The only time I drove it I let the rpms climb more to where I felt it should boost. Other than that I haven't revved it to high.

 

[rlacasse1]

Yay. She's running good. The knock sensor cleared up all the issues. It runs cooler now. The manifold quit getting so hot and the coolant quit boiling over. So it must've had the timing retarded to he point where combustion was happening way to late. Now I just need to run her for a while to get her cleared up from sitting.

BTW f*ck ever changing a goddamn knock sensor again. That sucked.

 

[Chicken Patty]

Yay. She's running good. The knock sensor cleared up all the issues. It runs cooler now. The manifold quit getting so hot and the coolant quit boiling over. So it must've had the timing retarded to he point where combustion was happening way to late. Now I just need to run her for a while to get her cleared up from sitting.

BTW f*ck ever changing a goddamn knock sensor again. That sucked.

What did you have to take off to change it?