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Discussion Starter #1
Greetings All. I have been lurking through this forum for the last year getting much helpful information. So far I have been able to find everything I have needed from old posts..until now.


A week or so ago my 1997 T100 RWD Automatic had a water-pump failure. Unfortunately at the time my Temp Gauge was not working properly ( it would go straight to center on startup ) so I ran the truck hot before pulling over and getting towed home.


I replaced the water pump and timing belt, but after getting it all back together and starting it I noticed a rough idle and some water dripping out of the tail-pipe.


I pulled the plugs and did a compression test on all cylinders. They were all at 175 ~ 182; however, #3 spark plug was wet, and looking down with a flashlight I could see a bit of coolant down there. It was clearly coolant and not oil or gas: smelled like coolant, plug was red like coolant, it talked like coolant..


From everything I have read, it sounds like that head needs to be pulled and taken to a machine shop ( or replaced ). I feel like I can do this, although I am short on money after just replacing the water pump, gaskets, timing belts and other belts.


My questions for the forum at large:


- Is there any technical reason that both heads need to be done? Can I get by with just doing the one for now?


- From my research so far, it sounds like I need to make sure I get the correct sided gasket (for the right side), and use the most recent OEM gasket. The part number seems to be 11115-62071

I also need to buy new Head Bolts, and new gaskets for the exhaust and valve covers. I also have a new knock-sensor harness in the shopping cart, as I have read they get brittle and usually need replacing.





....is there anything else I should be looking at while in there, bearing in mind that I am maxing out my budget already and really just need to get this project done so I can go back to my busy but happy life?


forgot to mention that I already have the FSM volumes 1 and 2. In fact, I just last night finished running the entire thing through a scanner and OCR software so it is now a searchable PDF.
 

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Welcome to the forums! :)

There really aren't any technical issues about just replacing one head gasket. It's just normal in a shop to replace them both since the timing belt is off and at least one head is being sent to be worked on. If all you can afford is one side, then that will have to do. ;)

When you replaced the valve cover gaskets, did you replace the camshaft housing plugs? These are about 50mm in diameter and look like a rubber covered cap. If not, here's the part number. ;)
PLUG, CAMSHAFT HOUSING
11188-62010
2
$11.11

You'll most likely need new o-rings fer the fuel injectors. It probably wouldn't hurt to clean the fuel injectors or have them refurbished. ;)
 

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Discussion Starter #3
Following up on my head-gasket job:

After talking with a mechanic friend, I decided to do both head-gaskets. His rationale that persuaded me was this: When a truck overheats, it does not overheat on one side, but evenly across the whole engine. Even though I was only having issues on the right head, it still could be that the left head gasket was on its way out and could go at any point.
I would save myself a lot of time it I went ahead and pulled the other head and put a new head-gasket on it, even if I did not take it to the machine shop.

I followed his advice and pulled both heads. Visual inspection revealed a crack on the left head on the cylinder that was failing the leakdown test. The right head looked good with no cracks or detectable warps. I replace the right head with a new gasket and new head gasket bolts.
For the left head, I found an inexpensive used head on ebay from a seller with reputable feedback. The machine-shop in Modesto did a nice cleaning, changed the valve stem seals, machined the surface and tested it for a reasonable amount ($175 out the door).


I watched a series on youtube where a guy did the heads on his Tacoma. It is a great 6-part series that walked me through everything.

A couple of mistakes I made were:

when putting the camshafts back on the left, I dropped a bearing-cap-bolt. down it went into the oil drainage port. I borrowed a scope from the Napa and saw the bolt in the oil pan. The oil pan is not an easy job, so I removed most of the bolts and lowered the oil pan edge an inch or so to get a magnet stick in there and fish the bolt back out. i then cleaned the pan edges really well and sealed it back with a new tube of the recommeneded gasket-goo. Took me the entire afternoon, but got that dang bolt out.

After getting things put back together and starting the truck, I got rough idle and CEL. The code was for the camshaft position sensor ( P0340 ). Taking the upper timing belt cover off, I was able to see that I had pinched the CPS wire behind the shroud that holds the fan on. I had to remove that, get the wire back, take the CPS off and test the wires to make sure they were not broken, then put the whole thing back together.
CEL went away and idle is normal.
Went for a test drive and everything is normal so far, except my oil pressure is lower than it was before all this. I am not too worried about it since so many people have low pressure in their t100's. but I will probably drain a quart and replace with some lucas to bring the pressure up.

So now my truck has all new gaskets on the upper part of the engine, water pump, all belts replaced, and an oil change. Hopefully this will be it for a while, but after all this I could probably tear the whole thing down without watching any videos, so that is empowering.
 

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Remember that pressure doesn't equate to flow. Oil flow is vital fer yer engine. If yer really worried about the pressure, install an aftermarket digital or analog oil pressure gauge on one of the ports coming off the oil pump. ;)
 

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Discussion Starter #5
Remember that pressure doesn't equate to flow. Oil flow is vital fer yer engine. If yer really worried about the pressure, install an aftermarket digital or analog oil pressure gauge on one of the ports coming off the oil pump. ;)
So what I am reading here is you are saying it is more important to have the right weight/consistancy than it is to worry about bringing the pressure up to please the stock oil gauge?

If so, I can live with that. There have been so many people posting here and there about their T100's not showing good oil pressure that I am not too worried about it.
 

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Discussion Starter #6
After some driving I started getting a p0171 code and rough idle. I read through some forum posts it sounded like the most likely culprit was vacuum leaks, or a possible bad o2 sensor.

I tried using an unlit propane torch with engine running, but was not detecting any leaks. I took the truck to my local mechanic friend who politely pushed me out of the way and laid-in with a brand new can of carb-cleaner. It took him about 30 seconds to pinpoint some spots where a leak was happening (we could hear the engine rev noticably higher when he passed over those spots) We found and replaced a few ripped vacuum hoses and the idle immediately went back to smooth.
No CEL, yet. He said there could be some more leaks but to drive it around and see if the light comes back on.

I realized after watching him with the carb-cleaner that I was being too timid with my propane bottle. I should have had it on full blast and really put it in close to different parts of the engine.
I also realized that pulling off all those old dried vacuum lines and then cramming them back on after doing the head-gaskets probably caused the rips.

I am adding "replace all vacuum and fuel lines" on my 'future projects' list.

Yet another lesson from this whole project
 

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Discussion Starter #7
I was still getting intermittent CEL, with code for misfire on random cylinders and P0171, along with intermittent rough idle. I hunted down a few more torn/stretched vacuum hoses, but also noticed (via the Carb Cleaner spray test) that my throttle-body seal was leaking.
After taking off the TB and inspecting, I realized I had put the gasket on backwards. While I had it out I cut out the flat spot of the hole (turning it into an O instead of a D).

I put a very thin layer of silicone gasket maker on it before replacing the gasket, since I read those were not re-usable.
I also removed the battery cable to clear any codes.

Sure enough, the truck fired up nicely. Took it for a long test drive and no rough idle or CEL. I checked for codes and there was a cylinder 1 misfire pending, so I will monitor that and check on it later, but it seems like this part of the project is finished.

For anyone going through similar issues, I would take the advice I read on this forum on many posts: don't just throw new parts at problems. It is better to try and track down what the actual issue is first. It was very tempting to buy a new o2 sensor, a new MAF, new injectors.... but my finances are low so I was sort of forced to look at the problems over the course of several days/test things out/try something new/test/retest....The only thing I purchased was new vacuum hoses for around $9.00
 

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There is a possibility that you will have to go back to what you were doing upon your engine reassembly.

Misfire (single cyl) with idle issues may not always mean ignition or emission problems but could also be related to fuel injection.

Misfire (multi/random cyl) could likely be timing matter. You could be one(few) teeth off.

I assume that you aligned you cams as per book (single dots - dual dots) and set timing belt just right. However, on initial crank (when you do it by hand) belt tend to slip due to poorly designed tensioner.

Keep us updated
 

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Discussion Starter #9
There is a possibility that you will have to go back to what you were doing upon your engine reassembly.

Misfire (single cyl) with idle issues may not always mean ignition or emission problems but could also be related to fuel injection.

Misfire (multi/random cyl) could likely be timing matter. You could be one(few) teeth off.

I assume that you aligned you cams as per book (single dots - dual dots) and set timing belt just right. However, on initial crank (when you do it by hand) belt tend to slip due to poorly designed tensioner.

Keep us updated
Yes, when I did the timing belt I checked and double-checked cam dots and timing marks, then re-checked...then turned the engine around 360 and checked again to see if the marks all lined up and they did.

I had considered that a slipped belt could be a possibility, only the idle and misfires were random. I assumed a timing belt off a tooth would cause continuous issues. Is my thinking right there? Or can a timing belt cause random issues?

After driving the truck for 10 miles yesterday evening, idle was no longer rough and I did not get any CEL.

The one misfire was a pending code. If it happens again I think it will throw a CEL, if I understand that correctly. I will post here if that happens.
 

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I've posted here all sorts of stuff I've experienced after engine rebuilt. Look for "5VZ vibration after rebuild" tread, may be some of it will be a help.

I remember with timing belt there was a little pain. When aligning belt on bottom crank it didn't perfectly align on cams. It had to be either 0.5 tooth early or past, something like that. I think it was finally set to past.

Also, if you have to pull harmonic balancer again (I believe now you know all about that PITA), it is way easier to move radiator and AC evaporator out of the way so you can slide socket on the long extension and use your impact wrench on that sucker.

Well let's hope you will dial it in.

BTW, that 5VZ Tacoma guy on youtube deserves a medal of honor because he spent some serious time to make head gasket RR mini series for folks like us.
 

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Discussion Starter #11
BTW, that 5VZ Tacoma guy on youtube deserves a medal of honor because he spent some serious time to make head gasket RR mini series for folks like us.
I completely agree with that! He could probably bundle those tutorials and sell access.
 

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Grr..misfire on 1 and p0171 are back.

back to the drawing board.
Compression test is suggested to rule out issues with the piston/valves. The injector would be the next thing to test. It could also be a bad o-ring on the injector if it was worked on. ;)
 

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Discussion Starter #14
Compression test is suggested to rule out issues with the piston/valves. The injector would be the next thing to test. It could also be a bad o-ring on the injector if it was worked on. ;)
Compression is 180 at cyl 1. Swapped injectors with new o-rings, swapped spark-plugs with cyl 3. Will drive around a bit and report back.

######

on another note, someone said that after doing head-gaskets you are supposed to re-torque the head bolts after putting 500 miles on it.
however, these bolts were torque, then turn 90 degrees. Is re-torquing something I should do? Anyone have experience with this?
 

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I believe the head bolts are torque to yield now. The head bolts on the engines we grew up with used the retorque method. ;)
 

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I believe the head bolts are torque to yield now. The head bolts on the engines we grew up with used the retorque method. ;)
Head bolts are Torque to Yield, that's one reason it's recommended to use a new set when doing a head gasket or top end work. I did mine 100k miles ago as you described with no issues since. All so on my MR2 last year.
 

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Discussion Starter #17
Well, p0301 is still showing up. I can clear the code and then drive around for 10 miles or so and it comes back.

so far I have:

swapped spark-plug
swapped coil
swapped injector/replaced injector o-rings
double-checked all connections
checked again for vacuum leaks using carb-cleaner (but it seems to be cleared up)
cleaned MAF and intake


The idle is no longer rough like it was when I had vacuum leaks. The temp seems to be stable. I am not losing coolant or oil. Driving is smooth. A/C is working fine. Heater works fine.



The only thing that seems off is my idle, which has low RPM's. In drive it is around 500, in park it is around 700 ~ 750. One other thing that is strange is when idling, if I turn the steering wheel either way, the idle will pick up to a more normal feeling RPM ( 800 ~ 900 ).

This makes me wonder if there is an hidden vacuum leak somewhere that is altered when the power-steering kicks in.
 

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One other thing to check is the wiring harness to the injector as well as the injector ground points. The ground points are the brown wires bolted to the air plenum by the Diagnostic connector on the left side of the engine. Pull the 10mm bolt and clean all the surfaces just to make sure. Carefully inspect the wiring. Just short of that, you'll need to use an oscilloscope or noid light on the injector wiring/connector to map the injection pulse. ;)
 

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Discussion Starter #19
One other thing to check is the wiring harness to the injector as well as the injector ground points. The ground points are the brown wires bolted to the air plenum by the Diagnostic connector on the left side of the engine. Pull the 10mm bolt and clean all the surfaces just to make sure. Carefully inspect the wiring. Just short of that, you'll need to use an oscilloscope or noid light on the injector wiring/connector to map the injection pulse. ;)
I just went out and cleaned those grounds. They were not on very tight. I sanded the connectors and the surface, wiped and re-tightened.

I have not had a chance to drive around, as my daughter is napping at the moment and I cannot leave...but I did start the truck and let it idle for a while...so far no pending misfires. I will follow up when I get a chance to go somewhere.
 

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Discussion Starter #20
I am still getting randomly occuring misfires on 1, but I think I am going to start a new thread on it.

As far as my head-gaskets go, everything is working great. My oil and water levels are not changing, no overheating, an idle is running smooth (after fixing all of the vacuum leaking hoses).

Also found out that the idle increasing when turning the wheel (when stopped) is by design, as it makes the power-steering pump speed up a little.
 
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