Will writes:
Hi Sajeev, I am heeding your call for more questions.
1) Can a crack around one of the intake system tubes (thanks, shopmonkeys!) to the right of the Throttle-Body on an ’01 MkIV Jetta GLS 2.0 be the source of a lumpy idle (+even decreased mileage)? -I think it’s the Y-Tube next to the PCV. (also: last time I checked, this pipe was something like $200 to replace new from the stealership)
2) How necessary is it to ‘Bed-In’ new brake pads on new rotors? (ala StopTech’s instructions) Reason being, I just [made the mistake of] put[ing] Mintex Red Boxes on with new rotors, but no bedding, and seemed to get wobbly cementite deposits within 1 month! (note: since then, have just switched over to mild-upgrade slotted rotors and stock ATE pads as an avoidance maneuver)
3) Is the Cabin Light switch easily+cheaply replaceable on that Jetta? It seems to have gone on the Driver’s door.
4) I have Kumho Ecstas on this car that show a higher PSI range. I think max is like 51PSI or something. If the standard spec is like 28/26 with Stock Michelins, then how much higher should I run the Kumho’s? -36PSI on all 4 corners?
5) Should I rinse/wash the car LESS frequently in the winter to reduce potential corrosion if I live in an area that gets lots of road-salt in the winters?
6) I had to replace my Front Rotors. -Will I Ever have to replace the rears? -Is their wear-rate like less than 1/2 of the Fronts?
7) When would an ’01 Jetta in the Greater-NYC area start rusting-out? -I had a MkII that kinda started falling apart, -nearly Fred Flintstonte-style.
8) In that same geographical suburban area (not IN NYC), how much -years/% does parking a car Outside shorten it’s useful life vs. Garaged? -In general? -By other US geographical regions?
9) Similarly, if I have a used car I want to get in the future that might be fragile, where should I get it from? -Arizona? SoCal? Nevada?
10) Does a Throttle Body or MAF ever really need to be cleaned? -Or are the forums guys just being really obsessive? -Aren’t MAFs EXTREMELY finicky and fragile to clean?
11) What other intake/induction system parts or valves/membranes should be given a solvent rinse, if you were to pull the thing apart? PCV? All the tubes? What solvent(s) to use?
12) Are there weird Throttle-Position-Resetting-Routines that have to be gone through if you Do pull the TB to clean it? -Would it screw up the ECU if you didn’t? Do I need a special Code-clearer like a VAG-COM+Laptop to do this?
13) If I re-do the shoes on Rear Drum Brakes, can I just slap the damn new ones on, or do I really have to shoot everything down into a catch-pan with that brain-destroying Brake Parts Cleaner Spray first? -Swear to God, even with a respirator on, and outdoors, the first(+last) time I used that s***, I got a mad, pranging headache.
Sajeev answers:
Let’s see if I can nail all of these via shooting from the hip. Quick draw and rapid fire: Best and Brightest, do your worst. It’s on…SON!
1. Yes, that’s a classic problem stemming from a vacuum leak. Which you probably have from what I read there.
2. I have no clue. That said, always break in new pads/rotors to ensure you don’t wind up with the problem you mentioned. While it might not be necessary on every car/pad/rotor, it’s just the right thing to do.
3. That’s a question for the forums, but since this is a MK IV Jetta, I guess this is neither cheap nor easy to replace. Considering the rest of the car, there’s a good chance I’m right.
4. Never base your tire pressure on the number listed on the tire’s sidewall. That’s the max pressure and has zero correlation with what’s ideal for your car. Most vehicles need 28-35 psi at each corner, but read your owner’s manual to know the truth.*
5. Yes. I never verified it (Houstonian, ‘natch) but the concept of pouring water in every drain hole and letting it freeze shut sounds like a great idea to me. Time consuming and pretty insane, but the theory that salty water can’t get in when all the holes are frozen shut really speaks to me. Oh, and never park in a heated garage for this reason. Park outside when its salty out there.
6. I’ve heard the wear rate is usually more like 80/20, unless you do a lot of towing.
7. Too many variables to make such a blanket statement. That said, when it looks rusty, odds are it’s starting to rust out: WOW OMG SON do I really get paid for this gig?
8. I doubt the mechanicals and electrics really care about inside vs. outside, but the cosmetics are another story. That said, my cars had to live outside for years, with no problems. I try to keep them waxed regularly, tinted my windows and use reflective windshield shades religiously.
9. Anywhere in the South or West where they don’t have much (if any) snow. Since this is a big concern for you, consider getting a quality rustproofing job when the vehicle lands in New York.
10. You don’t usually need to clean them, unless you over-oil a K&N filter or have a lot of PCV related issues. Many throttlebodies (TBs) have a coating that you simply cannot clean. My cars have very tidy MAFs and TBs, but they don’t sit around idling a whole lot, I know how to oil a K&N filter and they have well maintained PCV systems. Crudding/coking just ain’t gonna happen with me.
11. Anything EGR related is also a good idea. The EGR’s channels can be a big problem. And replace all rubber vacuum lines. I use a lot of carb cleaner (gloves, safety precautions, etc) to get the really tough stuff out of an intake manifold when off the motor.
12. Probably not, but again, a valid question for the forums. I wouldn’t trust the info elsewhere…especially from me!
13. Yes, it’s important to get all that crud out to ensure a perfectly performing drum brake. Wear a gas mask AND a poncho next time!
*Unless you have one of those Ford Explorers with the explody tires. The recommended 26psi in a truck like that was never a bright idea.
Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.
Regarding cleaning the throttle body and MAF, I disagree with Sajeev about the throttle body. Every time you turn off the engine, a phenomenon called “reversion” occurs. At least one cylinder is full of air/fuel (which includes material from the PCV), and is on the compression stroke. When the engine abruptly stops, this mixture “reverts”, or pulses back towards the throttle body, which is closed. It then condenses on the throttle bade, which is cooler than the inside of the combustion chamber. Due to gravity, a rime of gunk builds up on the lower part of the throttle body and the throttle blade – this is mostly in the INSIDE, so you can’t see it by looking at the closed throttle. You can see the stuff on the body by holding the throttle blade open with the throttle cable assembly.
Since resistance to airflow varies by the radius of a tube to the fourth power, a small amount of restriction on the outer part of the throttle body tube significantly reduces airflow at wide open throttle.
Sajeeve is correct in that many new throttle bodies are coated – usually with Teflon – but they can still be cleaned. Don’t put them in a tank of parts cleaner. Buy THROTTLE BODY CLEANER – not carburetor cleaner, clean with a toothbrush and paper towels. It’s not difficult at all. You can do a fair job with the throttle body on the car, a better job with the throttle body off.
As for MAF – the only time I’ve had to clean one was when I was using a K&N air filter. They have a very fine coiled platinum wire. When the engine is turned on, this wire is heated red-hot to burn off any gunk. Then an electric current is passed through the wire to keep it warm, and the incoming airflow cools it. The cooler it gets, the more airflow, which is how it works. First, never clean it when the engine has just shut down – it will be hot, and the thermal shock of the cold throttle body cleaner (what you should use), will probably cause it to break. If this happens you must buy a new MAF. Wait till you are sure it is cool, then give it a very brief shot of throttle body cleaner from about a foot away – if you blast it too close the wire can break – it is VERY delicate.
I would say if you use a conventional air filter in good shape you will probably never have to clean a MAF. Since the MAF is upstream of the throttle body, reversion doesn’t affect it. Oh, and never ever dunk a MAF in parts cleaner.
You are correct sir…I have wiped down throttlebodies with a wet rag to clean them, but the specific cleaner should do fine.
So much for getting them right on the first shot!
You should not use throttle body cleaner to clean a MAF, dedicated MAF cleaner or rubbing alcohol only.
“Paper” air filters often use oil or adhesives to retain their dirt too, so using one does not mean you’ll never have to clean the MAF.
When you shut down vapors in the crankcase travel up through it fresh air intake for the PCV system and since many draw that air from the intake tube right behind the MAF that can also lead to a dirty MAF.
Just to make my post interminably long – if you are going to the trouble of cleaning your throttle body – clean the idle air control valve too. The idle air control valve BYPASSES the throttle, with a variable, electronically controlled valve. Thus it has an intake upstream of the throttle body, and a outlet downstream of the throttle body – so it will get gunked up by reversion. The valve is actuated by a solenoid or small electric motor. When you start your car, the ECU senses the idle speed and opens the IAC enough to maintain proper idle speed. If the IAC gets clogged in the shut position you engine will start but will not idle – idle speed will go to zero as soon as the engine starts. If it gets stuck in the wide open position the engine will idle too high. The IAC valve will be attached to the throttle body. Remove it, and clean out the air passages with throttle body cleaner, toothbrush, and Q-tips. Don’t get throttle body cleaner in the electronics. The IAC valve may be staring you in the face and be a five minute job to remove – as it was in my 5.0 Mustang, or impossible to even see, requiring removal of the throttle body – a horrible multi-hour job as in my Sienna, where the throttle body resides under the windshield washer shelf and the IAC is attached to the underside of the throttle body – all of which has to be removed to ever get to the throttle body. ALWAYS use new throttle body and IAC gasket if you remove them – an intake air leak will cause all kinds of idle problems.
When you put everything back together usually the ECU has to “re-learn” the proper IAC settings, so the car may have a weird idle for the first 15 – 30 minutes of driving – then it should idle at the correct RPM.
I did a proper bedding instead of the usual couple mildly hard stops from low speeds around the block when I last replaced the front rotors and pads and it made a noticeable difference – the brakes feel fantastic and they’re just OEM rotors and pads – good grab and linear, consistent feel at any pedal pressure plus no wobbles, shimmies or shakes. I can really feel a difference after getting proper material transfer from the pad to the rotor, it doesn’t feel like the pad is just sliding on the rotor and that you have to generate pressure to create friction. Linear, consistent and predictable right up to the point where ABS kicks in.
I see you swapped the race pads back out for stock ones – that’s a good idea if this is your daily driver. Unless the only street time it sees is on the way to and from the racetrack, you’ll be better off with something closer to stock. Normal street driving just doesn’t get the brakes hot enough for race compounds to work right.
Sajeev, allow me to complement you on your fine taste in photos.
+1
It’s nice to see the LumberJetta back on the information superhighway (if you’re new to the ‘net, Google it, it’s not photoshopped!).
It’s always nice to be appreciated for one’s mad internetz skillz.
How does one accomplish a proper brake bedding procedure without being arrested? What that procedure asks you to do is unreasonable in even a semi-congested area.
You can at least do the first part (drive 10-20mph and slowly come to a halt) even if you can’t do the really fast stuff. Something is better than nothing.
The key to proper break in is not to come to a complete stop and allow excessive pad material to transfer to the rotor in one spot.
I live in an older residential area with a grid layout, so I just drive down the side streets, accelerating to about 40 mph and then braking firmly to about 5 mph at each intersection. Never coming to a complete stop, of course.
You do want to adjust your tire pressure when you get tires that have the 51 or 44 psi max inflation and they are replacing tires that had a max inflation of 36psi. In all three cases that max inflation pressure is where the tire can safely carry it’s max load. So you must adjust the pressure up 8 or 15psi from the factory recommendations to put the tire at the same load capacity as the pressure on the door sticker will give you with the 36psi tires it came with.
First time I encountered tires with a 51psi rating I was seriously scared. I had purchased new tires for the wife’s car and the shop inflated them to the factory specs. I got on the freeway and the car was all over the road. I expected they would be underinflated as the tires that I replaced were of the 44psi variety, the car was from the 36psi era, and they had been underinflated when they were installed too. Bumped the pressure up and low and behold the car drove properly again and the tires wore nice and evenly. Basically flat with a little extra wear on the outside edge due to spirited driving.
+1 on this. All of the cars in my fleet (everything from a Civic to an Odyssey) are running between 40-45psi with no issues at all.
Those of us that are old enough to remember the transition from alpha numeric tire designations (which load range B had a max inflation pressure of 32psi) to P-metric sizing (with 35 or 36psi as the max pressure) will remember that we were instructed to add 3-4psi to the numbers on the tire placard for the new proper inflation pressure. Unfortunately with the advent of the high pressure tires there has not been that widespread recommendation. Also once those OE tires are gone it is hard to tell whether they were of the 36, 44, or 51 psi variety and know that the info on the tire placard was based accordingly.
Tires that are rated for higher pressures are also rated for higher maximum loads. The air carries the weight, so the volume and pressure of the air determine the load capacity provided the tire’s structure is strong enough to contain it. When using the same size tire on the same vehicle the proper inflation pressure for even tire wear and proper tire temperature remains the figure written on the door card. Keep in mind that the contact patch size of every tire is determined by only two figures: the corner weight of the car and the air pressure in the tire. By over-inflating you’re shrinking your contact with the ground and overworking the center of your tires. You’re also removing compliance from the tire and transferring the job of absorbing impacts to the tie-rod ends, ball joints, wheel bearings, and suspension bushings.
No not when referring to passenger car tires that do not carry the XL or LL designation the 51, 44 and 36 psi versions all carry the same load rating. Now in the case of light truck tires you are correct. Change your load range B with it’s max pressure of 36psi for some load range C with a higher load rating to go along with their 50 psi max and you keep your tire pressure the same. Go to tire rack and compare some of the tires in the size for that Jetta. The Kuhmo has a load index of 91, max weight 1356 lbs, max pressure 51psi and compare that to the Fusion with a 91 load index, 1356 lb weight rating, and a 44 psi max inflation pressure. Same weight capacity but different pressures needed to achieve it. I’m sure if you spent the time going through all of the options in 195/65-15 you’ll find a bunch of other examples.
The best way to determine proper inflation pressure is tire wear. It will be a little different for every tire, but never more than a few psi different than the vehicle manufacturer’s recommendation. So go with what the door jamb sticker recommends until you have enough experience with that tire to fine-tune it.
Increasing tire pressure beyond that ideal point improves hydroplane resistance, fuel economy, and steering response but reduces traction, puncture resistance, and ride quality; while increasing center wear.
Tire pressure – the manufacturer recommended pressure is not in the owner’s manual – the proper place to check is the federally mandated sticker on the door jamb. Unless as Sajeev says – you have one of the Exploders.
Also check tire pressure when the tires are cold (driven less than a mile) – driving heats them up and can increase the pressure over 5 PSI, giving you a false reading. Check tire pressure monthly and as frequently as you have extreme temperature changes (10 degrees F = 1 PSI, so if you go from 80 degree days to 40 degree mornings, that can mean 4PSI which is quite noticeable).
“the concept of pouring water in every drain hole and letting it freeze shut sounds like a great idea to me. … Park outside when its salty out there.”
Wrong, Tex. Salt melts ice even if ambient temperatures are below freezing, that is why they spread it on roads. NY area does not get cold enough to where that would not be an issue, and cars in operation warm up.
Also, a warm garage lets the goop melt and drip off which is far better than letting it stay in place, although there are garage maintenance issues.
Rear Drum brakes on a Mk4 Jetta???!!!??! MK4’s got discs at all 4 corners. MK3s have the rear drums.
Regarding tire pressure. I ran my MK4 Jetta TDI at 42-44 psi an all four corners. This was common practice among the TDI guys because it decreased rolling resistance, increasing MPG. Another member pointed out that you may lose traction, but I drove slow enough that it wasn’t an issue. Living in San Diego, I didn’t worry about rain.
My current Ford Focus is spec’d at 32 psi at all tires, but I run about 35 psi. The tires are uni-directional and there is a void in the middle of the tire, so I don’t want to overinflate too much.