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#19063 of 19336 Re: two '09 Forester XT questions [kurtamaxxxguy]
May 03, 2011 (3:04 am)
Subaru fills the diffs with regular oil. I changed both diffs to synthetic at 10k, and the regular oil in the rear diff was already discolored.
The manual says:
"The 2.5-liter turbo engine is designed to
operate using premium unleaded gasoline
with an octane rating of 91 AKI or higher. If
premium unleaded gasoline is not available,
regular unleaded gasoline with an
octane rating of 87 AKI or higher may be
temporarily used. For optimum engine
performance and driveability, it is required
that you use premium grade unleaded
Be sure to use premium unleaded
gasoline of 91 AKI or higher for turbo
models. If other gasoline (lower than 91 AKI)
is used, knocking, reduced output
and poor accelerator response will
But several people on the Forester Forum have used regular gas in their XT, not noticed any problem, and asked why they should not do it. Evidently they drive so gently that they don't encounter knocking. One wonders why they have an XT.
The management systems of some engines allow the unrestricted use of both regular and premium gas. The Subaru turbo does not, but the Toyota truck V-6 does:
From the 2006 Toyota Tacoma truck Owners Manual:
(2TR-FE is the 2.7L I-4 and 1GR-FE is the 4.0L V-6)
2TR- FE engine - Select Octane Rating 87 (Research Octane Number 91) or higher.
1GR- FE engine - Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, use premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher.
#19064 of 19336 Re: Rod Knock [scrappy44] NOT!!!!! - TIMING BELT TENSIONER - YES!!!
May 04, 2011 (6:26 am)
Anyone with that diesel sound should insist on having them check the "timing belt tensioner". I have a 10 y/o 2002 OBS and have paid for numerous visits to the Subaru dealers in various states over the years to figure out why I have always had that horrible knocking sound. Well, turns out I suffered with the noise for 10 years (90K) for no good reason. I brought in my OBS to have my Timing Belt replaced. Turns out the Tensioner was defective all along!!!!!
I can't tell you how this has changed my opinion of Subaru mechanics. I don't know what they were checking all the times I left it overnight so they "could hear it in the morning". I have no idea how much time and money this irritating noise has cost me. Totally unnecessary.
So please if you have this 'clacking' sound in the front of the engine - have them check the Tensioner if all else fails. Especially if you are under warranty.
Scrappy was right on when he replied:
My dealer now has a stack of service bulletins copied about the cold start "diesel engine" sound that they just hand out to customers who complain--though they will check over the cars to make sure it isn't something else--like a bad timing belt tensioner.
Unfortunately, after the mechanic changed the Belt and Tensioner - he informed me that my 'left subframe' is so rusted, it may not be safe!!!!! Beautiful....
Anybody have any ideas about subframes.....it only has 91K on it.....bought it 8/2001 - it is a 2002 OBS Impreza?????
#19065 of 19336 Re: Rod Knock [scrappy44] NOT!!!!! - TIMING BELT TENSIONER - YES!!! [stackman1]
May 04, 2011 (6:35 am)
The subframe comes right out and could be had cheaply from a lower mileage Impreza from the same generation, preferably with the same engine just to be sure. (I think they might be all the same in 2002, but don't quote me.)
However it is a boatload of labor to replace.
I would shrug and move on unless we're talking serious perforation. Even in that case, I'd be looking to sell rather than repair unless you're dead-set on driving this car another 100k.
#19066 of 19336 Re: Rod Knock [scrappy44] NOT!!!!! - TIMING BELT TENSIONER - YES!!! [stackman1]
May 04, 2011 (7:25 am)
Hmmm, get underneath and determine if that rust has eaten into the frame! Surface rust is not a problem, but I would at least clean it and slap some rustoleum or whatever on it to slow it down. Who is going to care what color it is down there anyway!
Knock knock, have a few stories to pass there as well. When it comes to timing systems, if you are off the slightest bit in the wrong direction you will get that diesel noise. I had my 86 Toy Tercel do it to me about two years ago until the belt broke. Drove me nuts trying to figure it out. On went the new belt, set it all up correctly and noise was gone! Summation of the repair, belt had jumped time enough to cause a piston to tap a valve. Not good. Car still in service 10K miles later.
Another tapping noise will result if you use an oil filter that does not have an anti-drain back valve. AKA check valve. I had a 94 Subie in MO the first time that had tapped for years on a rear driver side cylinder. A valve tap noise. Even tapped after putting the correct filter on. In went 8-16 ounces of Marvel Mystery oil. Few miles later, quiet as a mouse.
As for Subie dealer mechanics in general, I give them a "c" at best for the ones I have followed. That same car had one bank off one tooth on the timing belt. But recently when I saw how that driver drives it, He may have caused it to jump. Heavy foot. I spent time explaining how you can make a belt jump time by putting your foot into it big time. Needless to say, I have gone back to looking for timing chains in cars now when buying new.
So, in short. Knock knock who is there....if you have a heavy foot take a very good look at all timing components when that noise happens! Pray you just jumped time a little and have done no real damage! Keep the engine below 3-4K rpms and only that when absolutely needed. Much higher than that and you run the risk of jumping time.
#19067 of 19336 Re: Rod Knock [scrappy44] NOT!!!!! - TIMING BELT TENSIONER - YES!!! [stackman1] [girlcarbuilder]
May 04, 2011 (7:46 am)
Thanks Guys. I have always tried to be very smooth with acceleration and shifting (got a manual). Plus this noise started pretty much right away and I made a point of taking it back repeatedly while under warranty. It is beyond me that they didn't catch it. When I realized the location of the tensioner - it was obvious to me and I am no mechanic.
Today I took my car to a local guy to fix my exhaust. My temporary weld to the resonator gave up the ghost after three years so I'll probably need a new 'b' pipe. However, I asked him to tell me if he felt the left subframe rot was a safety hazard. I will let you know.
Any other thoughts/questions I should ask, would be greatly appreciated. I really would like to drive this car another 10 yrs - that would only be 180k - supposedly doable by Subaru standards. But I certainly want to be safe.
I thought I was home free after the Tensioner riddle was solved.
#19068 of 19336 Re: Rod Knock/Tensioner/Subframe Rot - Help
May 05, 2011 (8:10 am)
Well just in case anyone is interested. I took my 2002 OBS in to a local mechanic and he verified that the subframe is in fact rotted. I can buy a new 2.5i 5 Hatch for 18k I suppose - but I am inclined to throw a couple of grand into the car and have him replace the subframe, rear rotors and my exhaust. I suppose once they start pulling things apart there is always the chance the price tag goes up but I know the guy and he fixes a lot of wrecks and is pretty good at subframes. The car is 10 y/o but only has 91k. I am old school and not into disposing of things that can be fixed.
(As noted previously, I recently resolved my knocking by replacing the timing belt and the faulty tensioner - which began this whole thread.)
I have had to replace the rear wheel bearings over time but nothing major comes to mind......
Anyone and all advice would be greatly appreciated!
#19069 of 19336 Re: Rod Knock/Tensioner/Subframe Rot - Help [stackman1]
May 05, 2011 (9:45 am)
That's not very old to be having that sort of rust. In what part of the country do you live? There must be some major salting issues....
#19070 of 19336 Re: Rod Knock/Tensioner/Subframe Rot - Help [xwesx]
May 05, 2011 (10:04 am)
The majority of the years were in St. Paul Minnesota.....
#19071 of 19336 Re: Rod Knock [scrappy44] NOT!!!!! - TIMING BELT TENSIONER - YES!!! [stackman1] [girlcarbuilder]
May 05, 2011 (11:25 am)
Unless the oil filter mounting was substantially different back then, I wouldn't think that the absence of an anti-drain back flap on the outer ring of ports would make any difference. On my EJ-25-2 engine, the threaded mount is straight vertical. Oil doesn't generally flow up hill.
I haven't used Marvel (basically ATF) in 30 years. I remember it did have some benefit to loosening up stuck hydraulic valve lifters on an old Ford. But you found it useful on a modern engine? Cool!
#19072 of 19336 Re: Rod Knock/Tensioner/Subframe Rot - Help [stackman1]
May 05, 2011 (12:08 pm)
I hate to be a doubting Thomas, but until I see it with my own eyes, I am not buying that diagnosis! Every unit from MO I have seen does not have that kind of rust on it. Years are '94, '97 and 03. All of them are very high mileage, 200K, 275K and 240k respectively and MO salts the roads in the winter!
Jack it up yourself and look!