low compression, engine rebuild or replacement
09-07-2011, 02:53 PM
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low compression, engine rebuild or replacement
Firstly hi everyone , great site learned loads been so insightful reading through all the threads ,
what i am wondering is i have a 2004 rx8 231 6 speed, and have been having warm start issues , starts first time when cold and seems like no loss of power however all my other cars have been simple small engined so i probably wouldn't notice.
I replaced the coils plugs and leads to see if this would make a difference but to no luck
so i put the car into my local mazda dealer for a compression test as pointed to across this site , now both rotars have low compression 5.4 bar per face at 250 rpm.now most of the threads seem to point at a new engine what my question is , is a new engine the only option , or would if i was to have the engine stripped and rebuilt replacing all the seals (refurbished ) also fix the issue or is my engine beyond repair now.
also what causes the low compression is this a issue with fuel injection damed seals or something else ?
thanks in advance
what i am wondering is i have a 2004 rx8 231 6 speed, and have been having warm start issues , starts first time when cold and seems like no loss of power however all my other cars have been simple small engined so i probably wouldn't notice.
I replaced the coils plugs and leads to see if this would make a difference but to no luck
so i put the car into my local mazda dealer for a compression test as pointed to across this site , now both rotars have low compression 5.4 bar per face at 250 rpm.now most of the threads seem to point at a new engine what my question is , is a new engine the only option , or would if i was to have the engine stripped and rebuilt replacing all the seals (refurbished ) also fix the issue or is my engine beyond repair now.
also what causes the low compression is this a issue with fuel injection damed seals or something else ?
thanks in advance
09-07-2011, 03:02 PM
#2
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It depends on the use of your car and how long you plan on keeping it. A rebuild is as only good as the parts being reused and the person doing the work. Mazda remans are hit or miss, one of mine lasted 74,000 miles.
09-07-2011, 03:05 PM
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A) It is VERY rare that an engine is beyond rebuild. Typically the only engines that are so destroyed as to not be worth rebuilding are ones that are detonated under high load forced induction.
B) Most "new" engines are actually re-manufactured engines, which is to say "rebuilt" engines.
C) Since rotary engines only have 3 moving parts, 5 larger stationary bit (housings/end plates) and a number of seals, rebuilding an engine usually requires replacing all of the seals and at least 1 housing or end plate, often more. Until you tear it down, you can't predict it. Rebuilds with just new seals are entirely possible, but your engine really hasn't been returned to normal still, as even really slow compression losses typically wear down something else around them at the point the compression is being lost through, and this will only get progressively worse.
Low compression is usually caused by lubrication failures. Either A) heat destroys the viscosity of the oil, and the oil loses it's ability to lubricate, B) carbon buildup starts unseating and wearing on the seals since it isn't smooth surface, or C) side seals overheat too much from too little oil injection to cool them and the springs deform until the seals break.
B) Most "new" engines are actually re-manufactured engines, which is to say "rebuilt" engines.
C) Since rotary engines only have 3 moving parts, 5 larger stationary bit (housings/end plates) and a number of seals, rebuilding an engine usually requires replacing all of the seals and at least 1 housing or end plate, often more. Until you tear it down, you can't predict it. Rebuilds with just new seals are entirely possible, but your engine really hasn't been returned to normal still, as even really slow compression losses typically wear down something else around them at the point the compression is being lost through, and this will only get progressively worse.
Low compression is usually caused by lubrication failures. Either A) heat destroys the viscosity of the oil, and the oil loses it's ability to lubricate, B) carbon buildup starts unseating and wearing on the seals since it isn't smooth surface, or C) side seals overheat too much from too little oil injection to cool them and the springs deform until the seals break.
09-07-2011, 03:07 PM
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thanks for the reply, i only really use the car for getting to work maybe like 2000-3000 miles a year tops , so a few years i would hope . the cost by the dealer for a replacement was in the Ł5000+ yet a full rebuild kit is Ł1000 ish ,depending on what other parts are needed once stripped. do you know if its the seals that cause the low compression ?
09-07-2011, 03:09 PM
#6
A) Low compression is usually caused by lubrication failures. Either A) heat destroys the viscosity of the oil, and the oil loses it's ability to lubricate, B) carbon buildup starts unseating and wearing on the seals since it isn't smooth surface, or C) side seals overheat too much from too little oil injection to cool them and the springs deform until the seals break.
Just to add- carbon also gets into the apex seals, which affects the spring tension
09-07-2011, 03:18 PM
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The good news is that even if you end up needing to replace major pieces, it's GOING to be cheaper than having the dealer do it. Only driving 2-3k per year, I would definitely recommend doing it all yourself. Save the cash, learn a ton, and have the pride when you finish.
There are several rebuild threads on here that you should read through to get a feel for what you will face along the way.
There are several rebuild threads on here that you should read through to get a feel for what you will face along the way.
09-07-2011, 03:21 PM
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The good news is that even if you end up needing to replace major pieces, it's GOING to be cheaper than having the dealer do it. Only driving 2-3k per year, I would definitely recommend doing it all yourself. Save the cash, learn a ton, and have the pride when you finish.
There are several rebuild threads on here that you should read through to get a feel for what you will face along the way.
There are several rebuild threads on here that you should read through to get a feel for what you will face along the way.
09-07-2011, 03:38 PM
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09-07-2011, 06:12 PM
#14
1000 pounds will barely cut it. That's just the seals and gaskets.
To ensure a proper, safe rebuild something more is required. Buying an used engine in good running conditions turns out to be cheaper where you live.
To ensure a proper, safe rebuild something more is required. Buying an used engine in good running conditions turns out to be cheaper where you live.
09-08-2011, 01:46 PM
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on the back of the rebuild if i do happen to buy a new engine and fit my self is they any major differences in the engines year to year so would a uk 2007 engine fit the 2004 rx8
thanks
thanks
11-20-2014, 05:11 AM
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hot start on rebuild.compression loss???
A) It is VERY rare that an engine is beyond rebuild. Typically the only engines that are so destroyed as to not be worth rebuilding are ones that are detonated under high load forced induction.
B) Most "new" engines are actually re-manufactured engines, which is to say "rebuilt" engines.
C) Since rotary engines only have 3 moving parts, 5 larger stationary bit (housings/end plates) and a number of seals, rebuilding an engine usually requires replacing all of the seals and at least 1 housing or end plate, often more. Until you tear it down, you can't predict it. Rebuilds with just new seals are entirely possible, but your engine really hasn't been returned to normal still, as even really slow compression losses typically wear down something else around them at the point the compression is being lost through, and this will only get progressively worse.
Low compression is usually caused by lubrication failures. Either A) heat destroys the viscosity of the oil, and the oil loses it's ability to lubricate, B) carbon buildup starts unseating and wearing on the seals since it isn't smooth surface, or C) side seals overheat too much from too little oil injection to cool them and the springs deform until the seals break.
B) Most "new" engines are actually re-manufactured engines, which is to say "rebuilt" engines.
C) Since rotary engines only have 3 moving parts, 5 larger stationary bit (housings/end plates) and a number of seals, rebuilding an engine usually requires replacing all of the seals and at least 1 housing or end plate, often more. Until you tear it down, you can't predict it. Rebuilds with just new seals are entirely possible, but your engine really hasn't been returned to normal still, as even really slow compression losses typically wear down something else around them at the point the compression is being lost through, and this will only get progressively worse.
Low compression is usually caused by lubrication failures. Either A) heat destroys the viscosity of the oil, and the oil loses it's ability to lubricate, B) carbon buildup starts unseating and wearing on the seals since it isn't smooth surface, or C) side seals overheat too much from too little oil injection to cool them and the springs deform until the seals break.
Last edited by sproog; 11-20-2014 at 05:24 AM.
11-21-2014, 06:25 PM
#22
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^^ get that compression test. You could have a poor rebuild (and of course the rebuilder is going to claim otherwise). This happens too often. Also poor ignition could lead to engine damage, entirely possible in the 18k since the rebuild.
12-12-2014, 10:20 AM
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possible hot start issue fixed..
So after finding out it was gonna costŁ120 for a compression test I decided to look a little more into things. I found a thread on here saying that they cured their hot start somehow with an oil additive called amtech engine restor, another saying that just replacing the ess done the trick and another suggesting a Seafoam like treatment using automatic transmission fluid can bring a seemingly dead engine back to life, due to freeing sticky apex seals. I decided to try all three, starting with the oil additive since I was due an oil change anyway. After a few hundred miles I thought it worked because for about 2 week after that the car started hot, not very well but at least I wasn't stuck waiting for the engine to cool. So at the weekend I don't the atf treatment and left it over 24 hours. While I was at ut I found and took the ess off to clean and it was completely black with almost an oily gritty coating all over. Am surprised it even started lol. I cleaned it up perfectly, connected everything back up and reset it with the brake stomp procedure. Anyway, I gave the car a good booting to clear the atf out and the next day I went for a 60 minute drive to another town. Once I stopped I trted starting the car out of curiosity, and it started perfect of the first turn of the engine pretty much!!! My engine management light also went out so am crossing everything in the hope that's me sorted. I'll keep checking to see if anything changes but that's the best few hot starts av had since owning the car and not sure a new car would start faster :-D.
12-12-2014, 10:25 AM
#25
Lol. I'm surprised people use these temporary fixes to "avoid" rebuilding an engine.
I'd only do such things for a few weeks while i wait for a new engine or for the parts to rebuild mine to arrive in the mail.
I'm surprised he didn't replace the fuel pump and cat as well since those items also play a role with difficult warm starts.
I'd only do such things for a few weeks while i wait for a new engine or for the parts to rebuild mine to arrive in the mail.
I'm surprised he didn't replace the fuel pump and cat as well since those items also play a role with difficult warm starts.