I am setting the timing and want to know if the belt must be on when setting the timing. Or can I line up the top and the bottom independently. The reason I ask is that I adjusted them both with the belt on, but when I was removing the pulley on the bottom it moved out of position.
Not entirely sure what you mean? Do you mean you are setting the ignition timing? Or all you setting the valve timing?
You must pardon my ignorance as I am by no stretch of the imagination a mechanic and am not familiar with the jargon, however i will attempt to explain what i am trying to accomplish. I am changing the water pump and timing belt on the 03 Jetta and try to set TDC. I was told the i need to make sure that the hash mark line up on both top and bottom or I can be off by 180 degrees, which I did with the belt on. In trying to put back the pulley, the ‘gear’ on the bottom moved, so it was no longer lined up with the hash mark on the housing, hence my initial question.
Every car is different, so consult your car’s shop manual before believing what I say applies to you. I change the timing belt on my Corolla myself. It’s a big job, more than most drive-way diy’ers will attempt, good on you for giving it a try. For me, the biggest problem wasn’t the timing belt alignment, it was removing the front engine mount and the need to jack and otherwise support the engine so that the engine mount could be successfully re-installed. Some drama there. It sound like you’ve got that part under control.
Back to the timing belt, I was careful in the un-doing part not to let either the cam or crank pulley move. So for me it was a simple matter to just push on the new belt. But after the new belt was on, I hand cranked the crank pulley around in circles a few times, taking out any slack, then I double checked the alignment marks were spot on, as spec’d in the shop manual. They were. There was no doubt the cogs lined up perfectly. If either the top or bottom was off a cog, I’d have immediately noticed.
So that’s the ultimate test. Put the new timing belt on best you can, then hand turn the crank a few times, see if all the marks line up. If not, make a note which way the change should be, move the belt a cog in the needed direction, and try again. Eventually you’ll get it to align perfectly. This job is apparently considerably harder if you have two cam sprockets to deal with, rather than like on my Corolla, it only has on cam sprocket, as Ray has noted on the show. But w/patience it can be done.
The 180 degrees thing. This can happen if you turn the crank pulley (or cam pulley) with the timing belt completely off. At that point you’ve completely lost all alignment knowledge. And there is no way looking at the timing marks to tell. It’s b/c with a 4 stroke engine, there’s the intake/compression revolution of the crankshaft, followed by the power/exhaust revolution. The camshaft position determines which of the two is being done for a particular crank revolution. So the crankshaft turns twice for every single turn of the camshaft. Look at the size difference between the cam sprocket and the crank sprocket, you know, where you put the belt. Count the cogs. There are twice as many cam cogs as there are crank cogs, right?
So there’s no way to tell by looking at the cam and crank timing marks if you are 180 degrees off or not. When the marks align, you’ll be at the top of the piston travel, but you may be at the top of the compression stroke, or the top of the exhaust stroke. There’s no way to know by looking at the marks. But it must be possible to figure this out, since they made the car work in the first place, right?
One way to tell which is which is remove the no 1 spark plug. Hand turn the crank (in the correct direction). You’ll notice on alternate cycles, there will be a big puff of air ejected out the spark plug hole. If you put your finger over the hole, you’ll feel the pressure grow. That is the compression stroke. So put a wooden dowel in there until it contacts the piston. Watch it go up and down, and note which of the alternating cycles you get a big puff of air out of the spark plug hole. TDC is defined the top of the compression stroke. Hope this helps. Be sure to follow your car’s shop manual procedure exactly though, as every car is different. Best of luck.
Why don’t you get yourself one of these, or something similar?
I have a slightly different one in my garage, and I use it for every FWD timing belt job I do at home
It is one of my most appreciated tools
@db4690 … did you forget to include a link?
Yes, I definitely wished I had that exact tool! Thanks @db4690 for the suggestion. Next time I do a timing belt I’ll either buy one, or if I can find somebody who rents these, rent one.
What I did, there was a photo of a similar tool in the shop manual, so I took that idea and made my own “fixture”, out of 2 x 4’s and plywood and a bunch of large j-bolts I had laying around. Conceptually it was the same, just made out of wood instead of metal. But it didn’t quite work out as planned. It turns out even an econobox engine like the 4AFE is pretty heavy, and the construction pine 2x4’s – even though they were reinforced w/plywood, flexed under the weight so that I couldn’t lift the engine enough to obtain the needed clearance. I had to resort to lifting from below with a jack too. When it came time to finish up the job and put the mount bolt back, it wouldn’t go. The engine had twisted slightly. And my “fixture” didn’t have the necessary degrees of motion to re-twist it into position. I was able to experiment by lifting at various points below, until I finally hit on the right combo to get the mount bolt in. Whew.
Yeah, you could buy an Astro or some other inexpensive brand, if you can’t justify OTC prices
I bought my engine support because the jack was actually in my way, and I got tired of tripping over it
Well…you will be happy to know that after much effort and YouTube videos, and consultation from my uncle in Trinidad via Skype, the job is complete. I removed the spark plug and used my antennae in the hole to find the TDC, installed the belt and turned the crank a couple of times to be sure they lined up. I tried looking for the mark on the flywheel but could not find the mark. (If anyone knows how to spot on a 2003 Jetta, please share.)
When I was complete with the install the car wouldn’t start. I checked all my connections and could not find anything, so naturally I thought that my timing was off. So I pulled everything down again,(there has got to be a better way to take that stupid mount off), and redid the adjustment, connected everything and the car still wouldn’t start. Finally found that the throttle position sensor was disconnect, you know I was pissed.
Once the TPS was connected the car started and it was idling rough. took it for a drive and it was driving fine. came back home and it was still idling rough. I disconnected the -ve terminal on the battery for about 30 seconds and reconnected it, and the idle improved significantly. Hope someone can explain that to me.
Well on to the next project…
Good on you @Kaska11 for getting it going again. Perhaps the rough idling was due to the ECM’s learning operation. It has to learn how to adjust the engine operating parameters after a change like this. It takes some time of driving and idling to do figure it all out. I’m not sure what the -ve terminal of the battery is, but what you did may have reset the ECM, and initiated the re-learning process. BTW, if you didn’t disconnect the battery before doing a timing belt job, in future, you should. It’s easy to create a spark or short which could damage something the electrical system with all the wrenching needed for a timing belt job. I always disconnect the negative connection on my battery on my Corolla before doing any serious wrenching. Just curious, why did you want to see the timing mark on the flywheel? You can’t see the engine flywheel can you, when doing a timing belt job? I mean unless you remove the starter motor for some reason. It would be a very unusual situation for the TDC mark on the flywheel not to match up w/the TDC mark on the crankshaft’s pulleys.
-ve = negative…There is no mark on the crankshaft gear that I saw. There is a mark on the pulley and the lower housing. I was looking for the mark on the flywheel just to be sure that everything was ok. Saw on YouTube somewhere that there is a mark there you can see to verify the timing. There is a small notch where you can see part of the flywheel.
I think there is a mark on the flywheel on my Corolla for TDC, but me, I don’t use that as part of the timing belt replacement. On the Corolla you can’t see the flywheel mark unless you remove the starter motor. But on your car they may provide a view port so you can, without removing the starter motor. Every car is different & to do timing belt replacement correctly & avoid damaging other stuff in the process you have to follow the car’s shop manual procedure.