I'm sure it has been mentioned before but I wanted to make a post so that others don't run into the same problem I had replacing my lower intake manifold gaskets.
I had a very slow coolant leak that was causing me to have to replenish the coolant about every two months. Found one leak coming from water pump. Replace that but coolant loss continued. I could smell coolant but could not see it anywhere. Once rate of loss escalated to once a month I decided to take action. I used coolant dye, which most parts counters don't know exist. It is made by same folks that make A/C dye. I waited until nighttime so I could see the glowing better with UV light. Put the system under pressure and sure enough there was a leak near the back of the intake on the drivers side.
Although it is a long and tedious job, it is straight forward until you get to setting the distributor back into the engine.
As it turns out, the factory timing marks on the harmonic balancer were not correct. Apparently they can be off due to shifting of the metal and rubber parts.
Save time that I wasted!! Manually TDC you engine. Do not trust factory marks.
Good Luck
Mark

 

There are two marks on the balancer. One goes almost straight down and the other lines up with the mark on the timing cover. With engine set that way for TDC #1, drop the distributor in with the rotor pointing to the 6 which is cast into the top of the distributor housing. Start engine and verify no SES light and P1345 (if P1345 present and engine still runs, you are a tooth off). If no P1345, check camshaft retard with a capable scanner and set cam retard to 0° ± 2.0°. It is not possible to adjust actual timing on these engines because timing is determined by the crankshaft sensor and the PCM. However, rotor position (as determined by camshaft sensor in the distributor) is important even if timing is not adjustable. Cam retard is NOT the ignition timing found on cheapo scanners.

 

In my case after manually TDC'ing the engine, the marks were nowhere close to where they should be. I didn't get out my protractor but the marks were at least 90 degrees behind (off). This makes sense since the clockwise rotation of the engine will cause slippage of the balancer on the rubber between the balancer and it's hub. We originally used the factory timing mark which resulted in no start situation. An internet search resulted in the info I have verified and am passing along to others.
After manually TDC'ing the engine it started on the first crank (After gas leak checks).
I also took the opportunity to "upgrade" the injectors from Central Port Injection to Multi Port Injection. It only cost an extra $250 incl. tax for a new AC Delco injection spider assembly on EBay. If you but it first you can save on gaskets too since it comes with needed gaskets. You will only need lower intake gaskets if you are going that far.

 

I would be spending my money on a balancer, if it had slipped 90°.

 

I am the original owner so I know the balancer has shifted from factory without any human help.
I won't be replacing it because I have done enough for now.
Here is my list since 1/1/2015.
Fuel Pump
Fuel Filter
Starter
Water Pump
A/C Overhaul (Complete Replacement of All Refrigerant Lines Radiators Etc)
Rear Brakes


It seems like every time I turn around something is breaking!! Then again it is 16 year old.

 

i never line it up to TDC. whenever i do a intake or replace the distributor i take the cap off and spin the motor til the rotor is facing straight back at the firewall then mark the firewall where the rotor is pointing and just put it back in the same spot you took it off. so as long as you dont crank or turn the motor for any reason you are good to go

s10s are pretty good about throwing a check engine line rather quickly if you put in the distributor one tooth off

 

Pointing the distributor to #1 is how I started. Then I got nervous about doing it that way and decide to "adjust" to TDC via the timing mark.
Anyway it is running now with "No" leaks!!!