dustrider

plugged cats difficult to diagnose without removing them or doing flow test

I bought an old '67 landcruiser basket in the '80's that "needs a head gasket"
having had a landcruiser previously for six years, I knew first hand how Landcruisers were notorious for blowing head gaskets
I changed the head gasket and it would overheat like old faithful even with good flow in the radiator. No water in the oil, no bubbles in the coolant stream
thought it was odd the way it would overheat . thought maybe I did something wrong with the head gasket

a garage mechanic put a smog test probe in the radiator fill and detected exhaust

I took the head off again and checked the block surface more carefully . Ran a sanding block on the surface and a red magic marker as a dye pen
found a tiny hairline crack between the top of the cylinder and a water jacket
you could barely see it so I missed it first time
hot compression was entering the cooling system

enapa

So maybe i should check for exhaust gases in radiator?

enapa

Now if i rev the crap out of engine it goes to normal temp instantly. Im thinking maybe a sensor is really corroded and when water flows faster it gets normal reading. Is that a dumb thought?

dustrider

if it is really overheating you will feel excess heat off the motor and pressure will blow out the radiator cap. the motor will ping and start to seize,
all a bad temp sender will do is scare you

dustrider

if a crack or failed head gasket leads to the cooling passages it will show on a probe, if you can find somebody to do it

enapa

It is not boiling over and engine doesnt ping. I would imagine i wouldnt be able to touch top radiator hose either. Its hot, but not to the point i cant keep my hand on it. Im going to change the sensor.

BMcEL

Test it before replacing it.

enapa

Where is the sensor for the gauge? The ecu one is on front of intake manifold right? Are they both the same?

enapa

Ok i found it. Took it out looks pretty corroded. Of course no one has one in stock lol. Guess i have to order one.

BMcEL

You can probably get away with cleaning it. Did you test it?

enapa

Dont have a way to test it. Finally found one local. Should have it in next couple hours.

post office

I love reading about other peoples problems . Let us know how it goes.

One thing i'm glad i dont have to deal with is overheating. Planning on changing coolant in a day or so. IS it still standard to change coolant every 2 years? I havent changed coolant for 5/6 yrs and am getting a bit concerned about it lol

The new jug of walmart green says its good for 5 years. I heard a while back that the anti build-up mechanism breaks down after 2. Confirm?

enapa

And that didnt work. So now its either hg on wrong or clogged cat? How can i tell if hg is on wrong?

enapa

Well i gutted the cat and that didnt fix it. So the only thing left? You guessed it. I actually put the head gaskets on the wrong side, drivers side on passenger and vice versa. Let this be a lesson to everyone....take your time and dont let anyone rush you. I feel like such an idiot. I just got the chance to tear down and i could tell it was wrong immediately. Cometely blocked holes. So for anyone having issues after head gasket change if your rig overheats only when driving and cools back down briefly when you rev the engine real hard then chances are your head gasket is backwards. On the brightside i now feel like a pro at doing this lmao. So if anyone ever wants any pointers send me a message and i will try my hardest to help you through it.

enapa

Also just so this comes up in a google search. If you lay down on drivers side of vehicle just behind front tire and look up to where head meets block you should see a big L on the corner of the head gasket that sticks out. If you dont then chances are head gaskets are on wrong side.

enapa

So this comes up in a google search. If you think your head gaskets are on backwards you can tell by laying down on drivers side and looking up to where head meets block and you should see a big L on corner of head gasket that sticks out. If you dont it might be that your gaskets are on wrong side.

Also one quick tip. You do not need to remove the exhaust crossover. Just disconnect it from downpipe / cat. To make install easier i highly recommend removing head with exhaust manifolds left on the heads. Just disconnect them from the crossover. Also the top most nut on drivers side exhaust manifold where it connects to crossover is easier to access if you actually get in engine bay and go at it from top. A ratcheting wrench set makes life much easier.

enapa

I will check this thread as often as i can so if anyone has any questions or needs a tip or two on changing the head gaskets in a 3.4 toyota 4 runner i can help.

enapa

One easy way is to lay down just behind front drivers side tire. Look up to rear corner of engine block and you should see a big L on corner of gasket that sticks out. If you do not make sure it is clean before you assume its not there. Now im not 100% sure if a non oem head gasket has the letters. I would assume they do.

JNetTrecker

It looks like I have the exact same problem! Only difference is that I just bought my 97 4Runner, 227,000 mi, 4x4 Auto. In all my troubleshooting and part replacing I found that the heads look brand new or recently sandblasted so I'm guessing it has had a head job very recently. No L showing on the bluish looking gasket that I can see :-/ I've replaced the following with OEM / Asian parts except Rad: fan clutch, radiator (O'Reilly & yes, flow through seems perfectly fine and no collapsing lower hose), thermostat (jiggle valve at 6 O'Clock & 1/8" relief hole mod at 12 O'Clock), ECT sensor, and coolant (twice). I've raised front end 22", belched, bled and pulled a static vacuum on the system to get all air out. No milk shake oil, bubbling in rad or antifreeze in exhaust. Only thing I haven't done is check the cat or muffler but I have no CEL's and exhaust seems to come out strong. According to Carfax the yota is a 1 owner & VERY well maintained.

Doesn't ever get to red but heats up to about 80-90% (bottom of red block being 100%) only while driving in Overdrive or slower speeds in 3rd gear lock up. Raise rpm and instantly temp starts to drop.

Any input on pulling the heads, part numbers needed etc would be awesome as I've never done it and am not exactly liking forward to it, lol.

DesertRatliff

In all of these posts and all of this wrenching, nobody mentioned that the jiggle valve on the T-stat (as per the FSM) needs to be in the 6 o'clock position.

My truck ran hot after I replaced my t-stat. I doubled back and realized I had installed the jiggle valve at 12 o'clock. I spun it around, bolted it back up and my truck runs 190-194F no matter what.