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Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

Hello all,

Does anyone have any knowledge relating to a bypass of the secondary air pump setup? I was wondering if it would be as simple as replacing the pump with a resistor so the ECM still 'thinks' its there.

Needless to say, mine is going (or went) bad. Don't want a CEL, but don't necessarily feel like spending $300 to replace this system that is used a very small percentage of the operating time. Car is parked in the garage so cat warms quickly in the morning without this system.

I appreciate that this is an emissions part but I hope you'll consider I'm not asking about "fake" 02 sensor resistors and removing the catalytic converter. Just this part that's apparently not even on all models with this engine. I could be commuting in my 10mpg El Camino, after all. Sorry for my lame justification...I needed it for myself.








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    Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

    I'm having what I think may be the same problem on my '98 V70. When I start up the car (and sometimes after the car has been running) I hear a loud fan sound for a minute or two and then it spins down. The dealer says its the secondary air pump that kicks on to presurize the brake system. They're claiming the bearings are starting to wear out and that I can just let it go until it actually fails. The problem is that it will cost ~$500 to replace.

    If this pump pressurizes the brake system, then I wouldn't want to trick the computer, but I am interested in replacing it myself. Can someone confirm we're talking about the same pump and also describe what it looks like/where its located? If it is under the battery tray, then it shouldn't be too hard to access. Any hints or pointers would be greatly appreciated!








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      Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

      First, as far as I know, there is no fan that pressurizes the brake system. If your pressure reservoir for your ABS is bad, that's totally different. BUT from the sounds of what your dealer told you, there's also nothing in the ABS with bearings that go bad. SO I think you're "being taken" or they aren't completely describing and therefore you are understandably misunderstanding them.

      The secondary air pump is an emissions part and runs at the times you are describing. It can be removed and you'll need to add in an 'oxygen sensor simulator' to fool the computer to think that the pump is blowing air through there. You can do a search for that on your favorite search engine. I used a $7 one off of ebay but there are very nice ones sold for about $40. It's basically a resistor that makes the rear sensor appear to be reading a leaner mixture than the front sensor.

      Also, the pump is a DIY job if you wanted to tackle it. Pumps from Audi, VW and BMW will fit and can be found for about $150 or less. I didn't want to replace mine for a few reasons (cost was the main one), but many will encourage you to replace yours even though it runs for only a minute or two each day.

      Anyway, if you want more info on eliminating it, you can contact me directly or do some searches on the VW sites about removing this pump. FYI, I left my valve in, just took the hose off. You'll understand this once you do your own. Have fun!

      Mike








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        Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

        Thanks for the reply! You're right about the brakes. The service desk guy didn't know what he was talking about when he told me it was for the abs brake system. When I picked the car up this evening I talked with the mechanic and he confirmed it was the air injector pump under the battery tray. He said the bearings are simply wearing out and one day it will just not do its job and trigger the CEL. Their estimate isn't $500, but $700! Geesh!

        I found the procedure for replacing the air pump at http://www.volvospeed.com/Repair/airpump1.htm (for those who may search this thread in the future). I also found a link for an air pump for $285 (hmmm. a link off the volvospeed.com site), but I'd really be interested in one of the lower price options you described.

        I'll search for the oxygen sensor simulator as a short term solution. In this case, would I simply remove the pump and plug in the sensor in its place?

        Longer term I'll want to replace the pump so the car will pass emisions, etc. You mentioned that pumps from other cars (VWs, Audi, BMW) could work. I'm guessing the part is pretty generic. What's the best way to find one? Would a pump from any model work?

        Thanks a lot for the info!

        Craig








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          HERE, this should HELP V70-XC70 1998

          http://www.matthewsvolvosite.com/air_pump_replacement_850.php
          --
          1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.








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    Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

    Thanks for the tip, BL!

    Does anyone have a schematic of this system? Are there flow sensors, etc? Thanks.

    Mike








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      Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998


      Mike,

      I just went thru this secondary air system thing on our 96 850. I don't know where to get a schematic of the system but it consists of 4 components that are very accessable. It has the blower (pump) under the battery tray, the SAS valve which is round and mounted up high on the engine near the firewall (has a purple vac line attached plus a black hose that runs down to the blower), the relay which is mounted near the blower (has three plugins on the 850) and a small selenoid control unit mounted on the inside of the radiator shroud. This has purple and white vac lines running to it plus a plug in connector. That's most of the system. To my knowledge, the SAS valve is what detects airflow (or lack there of) and turns on the CEL. My pump was bad. When I replaced it, the CEL went out on it's own within an hour. I've read other posts where the controller on the rad was bad and several where the SAS valve was bad but I think the blower full of water (design flaw) is most common problem. I don't know how one would "fool" the computer but there's probably a way. Hope this helps.








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        Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

        Consider this for a second, how is the SAS valve, which has absolutely no wiring going to it, going to detect airflow? Last time I was in an engine management class with Volvo the word was that it looks for a drop in the O2 sensor voltage (lower sensor values equate to leaner fuel mixtures) to indicate positive flow from the SAS pump. I questioned this as the air pump only comes on for the first 100 seconds when the engine is cold and the O2 sensor, albeit is heated, does not function properly until it is warmed up either. The answer I was got was that this was the information that they were supplied with and that was the way it was. At any rate in order for something to post a code it has to be monitored in some fashion. For instance the fuel pump, if you run out of gas do you get a code that says "you're out of fuel"? No you dont and it is because that circuit is not monitored for that so instead you get misfire codes. My point is that faking the computer out would be a tough thing to do and you might as well bite the bullet and fix the thing right and be done with it.

        Good luck,
        Mark








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          Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

          $300 isn't bad, compared with my 1998 Passat pump which was $800. $300 is a pretty much drop in the bucket for your car. Yes, the drops add up and sometimes look like a heavy flow. I would fix it right if it were mine, although the EE in me appreciates your idea. Maybe you'll post and say how it works?








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            Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

            It worked well. The surging is gone, the pump is gone, and a simple resistor setup is sending a fluctuating but reduced signal to the ECM. Since the secondary O2 sensor only reads emissions and doesn't control mixture, it hasn't affected my fuel economy at all.

            I actually tested it out without the 'simulator' at first and the car ran all week without a check engine light. Then it finally came on so I bit the bullet and strained my arms to reach the sensor harness, put the simulator in, and it's good to go. If the light comes back on, I'll post it right away, but it seems to work for every other make I've researched...no reason to think it won't keep working for my brick. There are mechanical ways of fooling the system, too. If you do some searches on headers and removing cats, they make a little spacer that moves the second O2 out of the flow a little and that effectively offers the difference in reading that the computer requires. I didn't want to try that one because it involved removing the sensor, which I really didn't feel like doing this time.

            P.S. - there's plenty of room under the battery for a cold air intake now...but if I were going to spend $200 for that, I would have replaced the air pump ;-)

            Thanks!
            Mike








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          Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998

          Going to run a capacitor and resistor on the 02 sensor (a common mod in the 'tuner' world when headers and gutted cats are installed) to fool the ECM into thinking the secondary 02 sensor is 'seeing' different readings than the primary. If it works, it's a cheap fix. If not, I'm out $3.

          Why bite the bullet if I'm not ready to roll over and die? :)








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          Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998


          Mark,

          Thanks for correcting me. The SAS valve, as you say, has no wiring and couldn't possibly turn on the CEL. I'm an idiot. I should have referred to the small control unit on the radiator that does have wiring plus two vac lines, one coming from the SAS valve. A poster several weeks ago was still getting a DTC (secondary air injection system: no flow detected) after replacing the blower and SAS valve. He replaced the little control unit and the code disappeared.

          bl








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    Secondary Air Pump - can it be bypassed? 'Fool' the computer? V70-XC70 1998


    If it's the same setup as the 850 (probably is) the pump is probably full of water and may run if you drain it. You can remove and drain it or simply drill a 1/8th inch hole in the bottom. After it dries out, disconect it from the relay (blue wire on the 850) and put 12v on it with a jumper wire from the battery to see if it runs.

    bl







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