This week's project is installing new fuel injectors (SC400). Are there any other preventative maintenance items I ought to do while the intake manifold is off?

 

Also, is anyone aware of a good tutorial for replacing the injectors? All I've found on the topic is the same unaswered question by others. The factory service manual has most of the process outlined (FI-26, page 2063), but it refers specifically to the SC300 in many of the steps (first I've seen of that in the manual) and may not be 100% applicable.

 

I decided to dive in today. No point wasting this ridiculously good weather for unsheltered engine work! I ended up finding this guide which provides more instruction than my copy of the factory service manual.

http://www.lextreme.com/starter.html

I've got the new injectors in, but I need to pick up a couple things tomorrow before putting everything back together and firing it up. The short, chubby air hose below the throttle body was in pretty bad shape, so it's possible I've had another vacuum leak all along. It looks like a coolant line, so I never suspected it of needing closer inspection. The small coolant line alongside it was a major PITA to get off, with the hose clamp having the pinch tabs below the throttle body and facing the intake manifold. I couldn't come up with any way to get pliers on the clamp, but I eventually wiggled it around toward me with a paint can opener to pull up on the lower tab while pushing on the upper ones with a screwdriver.

Not surprisingly, the clips for all 8 injectors broke when taking them off. At first, I thought that satisfying "click" was the tab disengaging nicely with a soft press, but I soon realized they were all so brittle they were snapping off instantly. I don't even want to imagine how much work it would be to replace all of those (at least now I have a clear understanding of how the wiring harness is situated alongside the fuel rails), so I'll be holding my breath and hoping that they stay firmly seated on the injectors.

I hope I never have to replace the starter, because it's going to be at least twice as much work as the injectors...

 

I got everything put back together today, having replaced a few more hoses that needed attention. I had drained the coolant for taking apart the TB and IACV, plus adding a bypass to the now unused EGR routing. I may need to drain it again in a few days when my new heater control valve arrives (if I can't just swap actuators), so I just added distilled water for now to be able to fire it up and test the injectors. At 80 degrees out, I figured that can't do any harm.

Anyway, when I started it up, there was a loud, repetitive knocking noise. I'm not sure what I could have done that would cause that... I didn't see anything making contact with the serpentine belt, so I shut the engine off in case it's something internal. My only guess is that I haven't added enough water to the coolant system yet. It takes a while to work its way through; I added more several times over a few hours and only had 3/4 ga in at the time of the test start. Could that cause such a noise?

The only other thing I noticed is a bit of water hissing out of the thermostat housing's gasket. I had taken the 'stat out to inspect it and it looked brand new, so probably replaced along with a tune-up that I estimate was done by the previous owner 5-10k miles ago. I guess that's why they say to never re-use a gasket...

As for the new fuel injectors, I don't see any visible leakage. The real test will be tomorrow to see if the fuel lines hold pressure and allow it to fire right up.

 

I think today's news is better... I added more distilled water to the coolant overflow, as the level had gone down more overnight. After looking everything over again to make sure nothing was left disconnected, I fired it up a second time and no more knocking noise! However, after at most a minute of running, steam started coming from somewhere below the throttle body while I was adding more water.

I added the rest of the gallon jug after shutting the engine off, and that seems to have it topped off now. That should be real close to how much I drained out via the radiator drain **** -- I couldn't get to the two engine drain ***** without jacking the car up, which I can't do on my steep driveway.

Would running just water as a temporary test cause steam that quickly? Obviously, it doesn't have any of the coolant's thermal qualities helping out, but I wouldn't have expected that in sub-60 degree morning weather and at nowhere near operating temperature. I don't see any leaks anywhere. Also, the thermostat housing stopped hissing water, but I'll still double check that when I drain the temporary water.

 

I had a half gallon of old coolant lying around that probably isn't good for much more than testing, so I added that while running the engine again. It still started steaming, but not quite as quick as it did with just water. It then occurred to me that the steam was coming from the area of the heater control valve which I have temporarily bypassed in the full cooling position, so I undid that and tried again with the heater on full blast. No more steam this time.

Is it possible that having the HCV closed was keeping coolant from fully circulating initially?

I thought I was out of the woods at that point, but then I noticed a bunch of water/coolant leaking down below. Took a bit to figure out it was coming from the bottom of the thermostat housing, so I've got it draining again to go back and inspect that o-ring.

 

I think I found the problem, but I'm a bit confused as to the proper path to take. When I removed the thermostat housing, I didn't realize it had a silicon sealant that's nearly identical in color to the metal. Replacing it without resealing it obviously doesn't result in two well-mated surfaces.

The factory service manual refers to it as the water inlet housing in the Water Temp. Sensor section (FI-99). For removal, it says to "Remove the O–ring from the water inlet housing." However, the only o-ring I have is the gasket around the lip of the thermostat itself. Is there supposed to be another o-ring that goes outside of that, to seal the water inlet (plastic) to the housing (metal)?

I'm further confused by the re-installation steps:

I think that's referring to the portion of the housing that the thermostat housing connects to, and the o-ring in (c) is for just the thermostat's inlet. The pictures are tough to make much sense of.

http://lexus.sewellparts.com/oem-cat...C400-1994.html

That shows a big o-ring, which I'm guessing is what I'm missing. Would it be safe (or more precisely, wise) to re-do it with silicon like the previous owner did, or should I twiddle my thumbs while waiting for a new o-ring to ship? Or better yet, has anyone come across a generic o-ring at auto part stores that fits?

 

I found the answer: Duralast/Felpro #35445. AutoZone lists it under Replacement Parts > Cooling and Heating > Thermostat Gasket instead of Replacement Parts > Gaskets, so I only found it when following a search link to other tstat gaskets.

Here's a bunch of info on using silicone sealants in place of an actual gasket:

http://www.corvetteforum.com/forums/...ng-sealer.html

Something like post #9 looks ideal for our housing, both sealing around the thermostat's lip and the mating surface between the plastic and metal, but finding measurements on any OEM replacement part ain't easy.

Edit: Confusion eradicated. I picked up the Felpro gasket and was surprised to see it's the exact same thing I've got over the lip of my thermostat, not an additional thing that sits on "top" of the tstat like I was thinking. However, the new one is much thicker than the old one, which makes me think the previous owner and/or mechanic was too cheap to put a proper gasket on there, instead using the compressed old one. With the old gasket, the two halves of the housing sat against each other without tightening down the nuts, thus the need for silicone. With the new gasket, there's about 2mm of gap before tightening the nuts. I haven't started the engine yet (still adding coolant/water), but no signs of leakage so far.

 

I suppose I should follow up with an answer to the original question. Before embarking on the project, I should have ordered the following new gaskets: throttle body, IAC valve, upper intake manifold (x4), and perhaps water inlet filler.

The TB and IACV are both paper gaskets. Both of mine had a tear in them, but I didn't have spares and didn't want to wait several days for a replacement (no Lexus dealer in town). The IACV gasket was only torn at one of the bolt holes, so that shouldn't affect anything. The TB gasket was more of a concern, having a tear all the way through one of the edges. The intake manifold gaskets are metal and don't really seem like they're likely to need replacing despite the recommendation to do so, so I'm on the fence about that one.

I do have a bit of a whistling noise after the project, but I'm unsure if it's a vacuum leak or just the fact that I'm listening to the engine much closer than normal and catching things like that. I don't hear anything with the hood closed and feels fine, so it very well could be my imagination.

That leads me to my question... Is there any good reason for the TB to have the coolant lines connected to it? Is it really being cooled by the circulation, or did Toyota just do that as a convenient connection? I'm thinking I should have just run a hose straight from the IACV to the hard line on the other side of the TB and made it 100x easier to take the TB off next time for putting a new gasket on. That sucker is so hard to get on and off in that tight little space.