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#1 |
New Member
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Location: California
Posts: 9
2003 L-Series 3.0L Wagon
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I drove my 2002 LW300 2 days ago and all was fine. Last night I drove it and it took a tremendous amount of foot pressure to get the car to stop. It felt as if the power brakes were not working. The brake pedal didn't seem very responsive. When I arrived at my destination and turned the vehicle off. I pumped the brakes a few times, held it, and started the vehicle. Th brake pedal didn't soften as expected.
I would appreciate any input on diagnosing the brake issue and possible fixes. Thanks in advance, I really appreciate it. 2002/LW300/V6 |
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#2 |
Master Member
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Welcome to SaturnFans, Brian90638! How long was the vehicle sitting prior to this trip? What was the outdoor temperature at this time? Semi-metallic brakes work poorly in very cold temperatures and effectively mimic the symptom of lost vacuum boost. As the brakes warm up then they act and respond normally.
Regarding the vacuum power booster: check the vacuum hose from the throttle body to the booster. The check valve is in the vacuum hose. A bad check valve will weaken the vacuum boost assist. If the diaphragm inside of the power booster has ruptured - however small that might be - then, yes, the brake pedal becomes extremely difficult to depress and the vehicle takes a much longer time and distance to stop. The only correction for this is to replace the power brake booster.
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345K miles - Holy canolli! Biden/Harris predictions, '21 -'25: weak economy; weakened military; increased terrorism; an emboldened RED CHINA. I fear that I will be correct. I'd rather be wrong. |
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#3 |
Super Member
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Brakes should work whether its sub freezing or desert heat. On L300s, the vacuum port for the power brake booster is on the rear intake runner. The hard nylon hose runs from the top of the round brake boost unit into the one way check valve then towards the midpoint of the intake runner vacuum port, a brass fitting. Examine all points on this vacuum line for damage, cracks in the vacuum check valve, hoses and fittings for vacuum leaks with the engine idling. A soft rubber grommet on the brake boost unit holds the hard plastic fitting in place. Power brake units rarely fail and likely the last on the list of failures if power brakes are lost. With engine idling, you may hear a vacuum leak if part damage occurred from wear and tear including old age.
With engine off, pumping the brake pedal should firm up on each stroke until full hydraulic pressure stops pedal travel around mid travel. This is under normal circumstances with the brake boost unit having a reserve (the check valve to retain vacuum within the brake boost unit) for several power braking attempts before reserve vacuum is depleted. This would occur when pumping the brake pedal after the engine's off. Once vacuum is bled from depressing the pedal several times, the pedal should firm up - hydraulic power without power assist. When power assist is lost while driving, the pedal should feel firm as your leg muscles are the only power to generate hydraulic pressure on the brake master cylinder without power assist. This translates into longer stopping distances since power assist isn't multiplying leg power.
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#4 |
Advanced Member
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Location: Willamette Valley, Oregon
Posts: 686
2002 L-Series 2.2L Sedan
2002 L-Series 2.2L Sedan
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My brake booster failed over the period of a few days not all of a sudden. The entire booster is out under the hood so if the diaphragm is ruptured you will not hear the leak inside the car.
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2002 L200/5 loaded, coming attractions B207R and F40, Now searching for Saab 9-5 knuckles and axles. |
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#5 |
New Member
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Location: California
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2003 L-Series 3.0L Wagon
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pierrot and fdryer, thank you very much for your suggestions/input. I'll examine the areas you suggest and get back with any new findings.
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#6 |
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2003 L-Series 3.0L Wagon
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It was relatively easy to detect the problem. It is a broken "brake booster check valve". It snapped at one of the hard plastic lines. Now the more challenging task is to find a replacement. The existing part appears to have a number on it of 060701. I checked at this one popped up at Autozone https://www.autozone.com/brakes-and-...archText=47424.
It looks identical but AutoZone shows this as not compatible with my car. Are there any major differences in 'check valves'? Advice? Do you have any tips for working with the hard plastic vacuum line to remove the currently broken check valve? I'm guessing heat? |
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#7 |
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Location: Speedway, Indiana
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2007 ION-2 Quad Coupe
1997 SC1
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The vacuum check valve is pretty generic.
A Dorman 47149 might work. Or hit the junkyard. Probably not a bad idea to replace both sections of tubing/hose also. Just make sure all your connections are tight. |
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#8 |
Super Member
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Unless Dorman makes the vacuum check valve in a smaller diameter for the hose end, (I have no idea, maybe 5mm/1/4" OD?) the universal Dorman check valve has a larger OD than our Saturns check valve. I tried checking my vacuum boost unit some years ago and broke the check valve when attempting to heat up the nylon tubing.
![]() The solution for me was to search auto parts store shelves for a custom made vacuum line setup. A Dorman right angle hard line with rubber fitting allowed me to reuse the Dorman part, long enough extension to fit a smaller rubber hose into the rubber coupling. The smaller rubber hose fits over the barbed brass fitting with a worm clamp. I just checked mine to see if it was worth a snapshot but everything is black on black so it's not viewable. The rubber coupling (about 3"long to grab the hard line and another line as a splice is cracked. I haven't lost power assist braking yet but will have to either make a temporary band aid repair or find a suitable replacement rubber coupler. ![]() My repairs became a nightmare with different fitting sizes to deal with. Hopefully you won't go thru a similar scenario.
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#9 |
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A follow up with one snapshot and possibly a better suggestion if the Dorman vacuum check valve has a larger O.D. barbed fitting than the original.
I removed the Dorman 90 degree hose extension from the Dorman check valve, sliced the damaged rubber coupling lengthwise to remove it and slipped the 6/8mm braided rubber hose over the plastic tube. With vacuum, one worm clamp was used on the brass vacuum port to secure it in place. Friction fit between rubber hose and hard plastic tubing (nylon or pvc) prevents this end of the hose from slipping off since vacuum tries to suck in all the connected parts. The 90 degree rubber fitting is flexible enough to fit over the non barbed Dorman check valve. The problem lies in two OD fittings; the brass vacuum port and Dorman barbed fitting. The Dorman barbed fitting is around 10mm+. The brass barbed fitting is around 6/8mm. Two hoses are needed with a plastic adapter to join the two different I.D. together. I cannot remove the brass fitting and replace it with a larger O.D. port to match the Dorman barbed fitting as I think its seized in the aluminum intake runner and fear damaging the brass fitting by breaking it into two or damaging the aluminum runner. Paring down the Dorman Barbed fitting allows slipping on the rubber right angle Dorman extension onto the check valve.
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#10 | |
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Location: California
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2003 L-Series 3.0L Wagon
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My setup is very similar to the illustration I posted. The check valve is located in the middle of the hard nylon lines between the manifold and booster. I haven't tried to heat the nylon lines to test their pliability. I will in the morning. If it turns out the 2 pieces of nylon line are FUBAR and not reusable, can I just replace them with rubber vacuum lines? Although I purchased/ordered the check valve I previously mentioned https://www.autozone.com/brakes-and-...archText=47424. I found this one https://www.autozone.com/brakes-and-...alve/98343_0_0 It seems a bit more like your setup. The check valve is part of the elbow that gets inserted into the booster. Is this ok as an alternate? Seems as though it would work and visually looks more like yours. |
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#11 |
Super Member
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Yes, I'm an expert at screwing up. Fortunately, achievements far outnumber mistakes. At least 2 to 1.........
Dimensions are left out in both items, a concern not mentioned in forums, especially when dealing with hard nylon vacuum lines. I don't recall if I saw both Dorman vacuum check valves. I probably did and that's probably when the nightmare screw up began. If I'm not mistaken, the inline check valve has both barbed fittings with small outside diameters (OD) than the plug in valve. If the inline is a direct replacement then the question is how does one remove the hard nylon tubing? As mentioned previously, service manuals state a hot air gun is recommended to heat and soften nylon tubing for easier connection/disconnection. A hair dryer may be in most households and may work. Commercial hot air guns allow regulating temperatures with adjustable intake air louvers. As hard as these nylon vacuum lines are, they have to be heated until they become rubbery. Protective gloves are needed to work on very hot nylon heated to a rubbery consistency in order to disconnect hoses from check valve. The plug in check valve is the one I bought that started my journey into the unknown of attempting to mix small diameter replacement hoses that fit the brass port to a large diameter plug in valve. ![]() I don't remember the original fitting on the brake boost unit. If the barbed diameter is the same as the brass fitting then you may be able to replace the nylon tubing with fabric braided rubber hose. My rough measurement of inside diameter is 6-8mm. This presumes the inline check valve barbed ends has the same OD as the brake and vacuum port fittings.
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#12 | |
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Location: California
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2003 L-Series 3.0L Wagon
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#13 | |
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2003 L-Series 3.0L Wagon
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![]() On another note, I had a check engine light for 6 months and couldn't get a good diagnosis. The error I got was for the 'mass airflow sensor'. After replacing the check valve I cleared my codes and took it for a test drive. Drove much better with the hesitation now gone and the brakes worked perfectly. This tells me, the little check valve has been cracked and leaking for some time now. Hopefully my experience helps others. Thanks again. ![]() |
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#14 |
Super Member
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Well now, you're the expert on hard nylon heating for removal of this vacuum check valve. Apparently I don't have the patience to wait for this *!%@×?;-< to soften as you dd. Better yet, you avoided stepping into the hole I stepped in. Anyone with this problem will be directed to you.
![]() I'm glad this turned out to solve two problems for you. |
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#15 | |
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2003 L-Series 3.0L Wagon
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#16 |
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hi fdryer- shocked , shocked that there was cussing going on. although to your credit fd, you did use icons to soften the blow. found your insights in this thread interesting. my booster is original , works fine and have never had to fool with it but have looked at the layout to anticipate the job. looks like it could be a mofo. my L100 has 188k so i guess it is ready to blow to hell. sorry. thanks tons bob f
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#17 |
Super Member
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rfisher, I'm only human and can react like anyone else when frustrated and having zero patience sometimes. I use symbols to substitute for foul words on public message boards. I can be more vociferous in person if I choose foul language. It depends on the people I speak to whether to use street terms or not. "When in Rome......."
Brian90638, in my limited time here, I don't recall any L300 with a faulty cam sensor error and replacing it. Service manuals describe it as secondary to the crank sensor because it helps the ecm provide cam sensor signals for better ignition timing. When the cam sensor fails, the ecm simply relies on the crank sensor. The crank sensor failing kills the ecm altogether since the em cannot run without crank sensor signals. The cam sensor connection is on the rear camshaft cover closest to the radiator.
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#18 | |
Master Member
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![]() BTW, I can end up cursing a great deal when irritated ![]() ![]()
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345K miles - Holy canolli! Biden/Harris predictions, '21 -'25: weak economy; weakened military; increased terrorism; an emboldened RED CHINA. I fear that I will be correct. I'd rather be wrong. Last edited by pierrot; 01-17-2021 at 02:58 PM. |
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#19 | |
New Member
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Location: California
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2003 L-Series 3.0L Wagon
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Last year I replaced the crankshaft sensor (bottom of eng near oil filter) because the car would randomly stall at a stoplight with the engine hot. That one baffled me for a week until someone here guided me in the right direction (possibly you?). It was a super easy fix and never had an issue since. With all of that said, should I replace the camshaft sensor or do you think there is something I should look at first? |
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#20 |
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Ugh,....... I'll get back to you after I drag out 50 lbs of service manuals and find P0343. I prefer to reply from an authoritative point of view holding a service manual as my reference. I trip on them all the time. It was wonderful when free access to an electronic library was available from a few clicks away on a mouse.
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