Hey guys,
brand new here. I just bought a 1990 4runner with 200K miles. Clean frame, decent interior but I bought it with the sole intention of learning to work on it. I figured given the age/mileage I would change the head gasket and timing chain not knowing if either have been done before.
I've gotten as far as having the intake manifold and valve cover off. It looks like the plastic timing chain guides are still in tact and, I may be fooling myself, but the guts look pretty clean compared to pics I've seen online. Just thought I'd share initial progress and ask if folks would gutcheck my initial perception of the motor.
cheers!

 

This looks cleaner than a near 25 year old engine with 200K miles on it.

 

Right? Not just me then. The Carfax report shows no indication of anything weird......

 

If it ain't broke, don't fix it

 

Stop. Look for any marking on the timing gear that could indicate it isn’t original. Might be stamped “usa” or something. Put the valve cover back on and drive it.

 

Even though there are plastic chain guides in there? I have the timing chain kit and gaskets. Why not just finish what I started? there is also the added twist that among the service records is a note from a mechanic who said he thinks the truck blew a head gasket ane he squirted some goo in the radiator to make it driveable. That note was relatively new and there was nothing in the records to indicate that the gasket had been replaced.....

 

"If it ain't broke, don't fix it" Best advice; already given.

You say: "...intention of learning to work on it." Chance of those plastic guides being original is infinitesimally small IMO. Not much to be learned by undoing work that has been done well previously. If you decide to tinker with your head gasket, be sure to read up on it, cuz lots of guys have had trouble with that one.

 

Make sure to replace the o-ring and two cushions for each injector. They don't reuse very well, and could seep gas.

 

I agree with the others; don't replace the head gasket just as a learning exercise. As you work your way toward the headgaskets, you will break things along the way. Just part of the beast.

At a minimum, do a leak down test. https://www.harborfreight.com/cylind...ter-64918.html These numbers aren't that useful unless you have a reference, so doing the test on a believed-good engine will give you a reference for later. If you really do have a need for more work, the leak down test will give you a lot of information (even without the reference).

 

It is hard to tell from the pictures, but the timing chain cam sprocket doesn't appear to have holes in it like the original Toyota one.

If the sprocket doesn't have holes in it, then an aftermarket timing chain kit was installed at some point. It is a good sign to have the guides intact. Is there any timing chain wear (grooves) behind the driver's side guide?

I agree with the others. If there isn't a problem now, I would just save those parts for later when you actually do need them.

While you are this far, you can check valve clearances.

I would check the condition of the rubber parts (belts, hoses, vacuum hoses), brakes and suspension.

 

The third pair of headbolts look strange.
Perhaps as if there are studs and nuts there. Not stock.

 

I agree. I think it's had a timing kit at one time or another.

Personally, I would drive it like it is. If the head gasket does have a leak later down the road, then fix it.

 

perhaps that's one of the reasons that they sold it? i wonder how that problem manifested itself, was combustion gas leaking back into the radiator? you can get a test kit for that from harbor freight.

do the spark plugs all look similar to each other? if one is too clean there could be radiator fluid in the combustion chamber.

my 22re engine had a slight crack in the cooling jacket of the block, passenger side at the back, just below the head gasket, very difficult to track down the exact location, easy to mistake it for a head gasket leak.

i would check the valve clearances, replace the valve cover gasket with a factory toyota gasket set, then drive it and troubleshoot for issues before tearing into anything.

 

Ok the timing chain is def. aftermarket, but given the head gasket reference in the records I decided to proceed.
The head bolts are all normal and oem as far as I can tell. Those two middle ones had a little oil on top which made them look like nuts. With that said, the the bolt behind that one was stuck in the head so hard that it took 2.5 hours of torch, impact, breaker bar, PB blaster, (repeat ad nauseum ) to get it out. when it finally came, it was thick with gunk that made it super tough to get out of the head. With the head off I see that 3 of 4 pistons are black with carbon buildup. The head gasket wasn't in great shape but its not clear to me if it was blown or not. That said, the worst spot in the gasket is where the head bolt was stuck so badly, making me wonder whether there was coolant getting into that bolt hole and corroding things.

Given the carbon buildup, I'm going to add new plugs, plug wires, coil, and distributor to the tuneup. Hopefully that solves whatever problem its having burning fuel properly.
I'm going to drop the oil pan and clean it out as well. I've read here about dropping the front diff to do that....

I "think" the oil pan goes back on with a form in place gasket. Should I add that stuff (or RTV?) to the head gasket or anything else as I reassemble?

 

• Sometimes you've just gotta follow your gut. Turns out one of the guides was cracked and would have broken off in the not too distant future.
• 
  

 

OSK is a very good chain kit. Imho, the tensioner is the often the Achilles Heel in cheaper kits.

 

Head gasket should go on clean and dry, with the head and block deck surfaces degreased with acetone.
Use no sealants.
It is very important to chase the head bolt threads so that the bolts run in cleanly and can be torqued equally to the correct value.

 

Good Eye!