I have a 1998 Mazda Protege LX with the 1,5L engine and I noticed a small crack going across the Exhaust Manifold. I was told by the previous owner that because of that crack the car burns oil (even though the engine seems greasy and dirty), sounds loud like it is missing part of the exhaust(even though it has the entire exhaust), The entire car shakes whenever the car is idling (either at a red light or whenever the car is stopped) and it feels like the car feels like it is going to stall at any minute. Also it throws a flashing check engine light. I wanted to know if those are the actual symptoms of this car with a cracked exhaust manifold? What other damage do I anticipate?

I just bought the car knowing it had the damage but will replacing the cracked exhaust manifold fix all the issues that I mentioned or is there more damage to it than what I think I know?

 

The symptoms are correct..except for the oil consumption. In my opinion it should have no influence on oil consumption. Someone correct me if I am wrong, please.
Primarily 3 things happen:

1. Shock waves exit and cause a racket.
2. Exhaust back pressure is reduced and causes rough idle and so on.
3. Air enters the exhaust system. You may think that's not possible because there is pressure in the exhaust, but you would be wrong. The pressure goes in waves and behind a wave follows a low pressure period. That's when the air gets sucked in.

Secondary damages will come from this air entering the exhaust. The excess O2 will overheat the pre-catalytic converter and the catalytic converter. That is why your CEL blinks.

I would recommend fixing the manifold but I am not sure if it is worth it. I suppose it has way more than 150K on it (something you should tell us). Therefore I suggest determining the health of the engine. A compression test and a cylinder leak down test will tell you most. (Considering you describe the engine as grimy I keep my optimism locked up in a strong box).


If this checks out good then the oil is lost in the valve guides. You at least need new valve shaft seals.
If you fix the cracked header, you will have to see if the catalytic converters have survived the ordeal.

And we haven't even looked at all the other deferred maintenance.....

I hope you didn't pay too much for the car.

 

Couple of threads to view:
https://www.mazdaforum.com/forum/maz...-3-0-v6-29854/
https://www.mazdaforum.com/forum/maz...3-0-ltr-30510/

Even though this is on my Mazda 6, should still apply. You can get exhaust manifolds with pre-cats attached from Magnaflow (2nd thread to view)
Extra air in exhaust manifold may throw off O2 sensor.

 

Ok from what I know the engine looks dirty and grimy I originally thought it is leaking from the valve cover gasket and being burned off, the crack is pretty much right before you get from the manifold to the flexpipe toward the bottom, I only said burning oil because when you start the car you can smell the burnt oil along with exhaust fumes from the crack in the manifold. They seller originally told me that they replaced the entire exhaust from the catalytic converter to the muffler. The flex pipe looks somewhat rusty but I can't see if there is a hole in that. I know that the exhaust manifold cracking was a common issue with the 2G protege (1995-1998) especially the 1.5L engine. When you accelerate the car sounds very loud and when you are pressing the brakes or idling in park mode you feel the entire car shake and the entire exhaust shakes too. I didn't go to autozone or to a mechanic to get the check engine light read yet, and I plan to do that soon. I also thought it was a misfire but I won't know that until I guess after the exhaust manifold is replaced.

 

The mileage on the odometer is 155,568

 

If you can see a black spot on the flex pipe, that's where it's leaking.
Chances are you are leaking and dripping on exhaust as well as you should change your PCV valve (changing PCV valve should be done as Mazda doesn't do it and it's the first thing to do at sign of burning oil as well as a seafoam treatment to loosen up oil control rings). Sometimes I smell a burning oil leak as well. A lot of work needs to be done on your car: possibly plugs, ign coils, clean throttle body & MAF.

 

Alright, Christopher. It is not looking as bad as I thought and I can let my optimism out of the strong box.
Does your engine actually consume major oil? 1qt in 600 miles would be bad. 1 qt in 1500 miles would be fine. I am asking because all the things you need do add up. But you have a decent exhaust from the cat back. That's a +. If the oil consumption is not excessive or the compression test turns out decent it will make sense to fix the exhaust manifold and flex pipe.
Also clean the catalytic converter with one of these two methods in this video: I have used the 1 gal of lacquer thinner (NOT PAINT THINNER!) in 1/2 tank of gas method. If you do that you get a complete cleaning of the fuel system and intake valves as well. It saves you the "Seafoam" job.

Then check or simply replace the ignition parts as Noggin suggested, replace the PCV, clean the MAF sensor, clean the throttle body.

Then take out the EGR valve and clean it and the orifices in the intake manifold. Replace the vacuum lines. Get 15' from the reel for cheap. Open the clogged up nipple at the back of the intake manifold with a strong piece of wire.
Check the air intake hose along the ribbed section for cracks and use duct tape if you find any or if you are in doubt.

I don't know how much the manifold and flexpipe are but the rest should set you back no more than $100 to $120.

If your compression is o.k. you won't believe how well this engine runs after these fixes.

 

^^^^^^What he said!
Nice write up Tan!

 

Then it is not a good sign because I just reached the owner prior and she tells me she usually will top the oil off every 500-700 miles so not sure if that's bad or not. She also told me they only use synthetic for oil changes and refilling oil and that every 2000 miles she would use the fuel injection treatment by STP or Lucas. So according to her the car should be in great condition once the exhaust manifold is replaced but that oil burning and refilling seems really bad.

I might have to actually start looking for 1.5L replacement engines or look for a 1.8L Swap.

If it makes any difference I didn't have to pay that much for the car at all, but I am worried about all these repair issues that are at attention. My schedule makes it hard for me to dedicate some time to rebuild the engine that I currently have or even go to autozone to get the blinking check engine light read.

The mechanic they go to told the previous owner that the oil burning is due to old age of the car and it is NOT thing of great concern, probably a bad valve cover gasket or oil filter that it burns because of the crack in the exhaust manifold.

Also something I saw that was weird was when I first saw the car at the seller's place I noticed a burnt and ripped wall power cord (the one with 2 prongs and the round ground prong to plug into a house wall.) Tied around the engine near the lower right side of the engine bay, I asked the seller about that and she said that the owner before her lived in a very cold area and had to plug in a engine block heater into the wall to keep the engine from freezing temperatures. I am still not sure why the hell the ripped power cord is there and if that might play any role in the car acting the way it does aside from the exhaust manifold crack.

The previous owner said she use to drive it in that condition for a few months going about 55mph or 60mph on the highway without any issues. She just wanted to get rid of the car off her insurance so she could buy another one.

 

I am going to refer you to my earlier post, post #6. That burning oil could be caused by what I said.
Also synthetic oil is thinner. You could go up 1 value in thickness in oil when using synthetic. ie: if it calls for 5W20 you could use 10W30 in warmer 1/2 of year then switch back to thinner for colder 1/2 year