posted by
someone claiming to be Todd Traver
on
Mon May 24 13:54 CST 2010 [ RELATED]
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I had to replace the one on my 1993 240 at 250,000 miles. My prior 1990 240 had 225,000 with no MAF problems . Was mine failing at 250k just a fluke ? Or does the MAF have a finite life span ? Seems since that it's sort of like a light bulb filament it may have a limited useful life.
Reason I ask is, I installed a used unit of unknown year / mileage on another lower mileage Volvo 240 I have and was wondering if I should consider buying a new unit as I plan to run this car for the next several years and don't want it stranding me someplace .
Be curious to hear other peoples experiences...
Thanks , Todd
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The critical factor is whether your air filter box's thermostat (not the coolant thermostat) is working. If it fails, it fails in the mode that continuously directs hot air through the AMM (Air Mass Meter), destroying it.
I would suspect that you could have avoided killing it if you either:
1) check the thermostat regularly, or
2) (as I and many others have done) ripped out the flapper mechanism and rid yourself of the liability of that thermostat, and blocked off the orifice for hot air into the filter box (you can leave the preheat aluminum tube for inspectors to see).
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My first one lasted from 10 December 1984 until mid July 2009. Hopefully the next one will last as long. That was mostly in the South, including Florida for several years. Keeping the hot air tube away from the exhaust manifold should help a lot.
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Most of the electrical item on LH xx systems seem to last about 12-15 years in my experience. The electronic elements, coils, bi-metallic elemenmts, connectors, potting, plastic encapsulation etc, begins to fail from aging, corrosion, thermal stress and breakdown.
AMM's are not any different, as both the filament wire and potting go bad. The earlier heated wire seems to last the least, and later platinum un-heated foil type lasts much longer, but still not forever.
I think a lot of the life cycle is due to climate and how the car is driven and the temps seen in the engine compartment, more heat = lasts less time, air box t-stat withstanding.
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posted by
someone claiming to be Todd Traver
on
Mon May 24 15:11 CST 2010 [ RELATED]
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I live in the northeast where is can get mega-COLD here in the winter , so want to keep hot air induction functional . I just ordered a new airbox thermostat from FCP , cheap insurance at $ 9 . Thanks for your responses !
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"I live in the northeast where is can get mega-COLD here in the winter , so want to keep hot air induction functional."
It gets cold here in Central NY too but I have no trouble starting and running with a cold airbox.
This subject has been tossed around here a lot, and the consensus seems to be that the heat effect is of minor significance. One credible (to me) theory is that it slightly reduces emissions during the first few minutes of warm up. I'm fairly familiar with FI operation and don't believe there is any need to heat the air as far as starting and running are concerned.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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It'll nudge your winter fuel economy up a touch as well, since the car is sucking 60*F air vs. much cooler air.
That said... I just realized that all of our cars have good T-stats, but no flex hoses to the manifold. I'm not sure what I've been trying to achieve there! :-)
-Ryan
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Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sway Bars, GT Braces, Dracos
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars
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+1 to that.
Have tested and run w/& w/o air box t-stat over a 10 yr time on 2 245's and when the outside air temps get below 35 deg F it can make up about 2-3 mpg difference.
Look at the airbox inside. Do you see that long conical pitot tube?
It is intended to bring in outside air to super-cool the t-stat while running. When the temps are very cool, the damper closes (sometimes partially) to maintain a warmer air temperature when running, not just when starting. It WILL improve tne engine running efficency and MPG up to ~2-3 MPG, and this is especially true for highway speeds at sub-freezing temperatures.
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Without the failing thermostat in the airbox, they last forever.
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Without the failing thermostat in the airbox, they last forever
Forever is a very long time :-) None of my Volvos have hot air from the exhaust manifold ducted to the AMM and I have had at least one AMM fail for what have to be other reasons.
Randy
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Ditto.
The "burn-off" function heats the filament briefly to like 1,000*C... which is literally hot enough to melt some kinds of rock... every time you shut the car down.
At some point, somethings gotta give.
-Ryan
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Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sways/Braces, Dracos, A-cam
1990 744GLE 189K 16-valve project
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars
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You can give them a much better chance at a long and happy life if you disable the flapper inside the airbox, and glue it down so the hot air intake is blocked.
Other than premature death by roasting, they are little enigmas. Most people simply carry a known good spare rather than preventively replace them, as new/rebuilt ones are expensive. I've scored a few recently-rebuilt units (Injection Labs sticker on them) from the junkyard for $25 each.
John
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