3FE Engine Help, head gasket? (1 Viewer)

[RocketCityCrzrs]

OK guys, let me try to do the best explanation i can on this. I have an 88 fj62 with the 3fe in it. Bought the truck 4 years ago and the motor was toasted. I pulled it and did a full rebuild, slapped it back in and drove the bejesus out of it for the last 4 years as a daily. The engine had about 15k miles on the rebuild when back in February, i started her up one morning and she was smoking like a train. It was white smoke and drained the radiator then started to overheat. I shut the motor before it got to the top of the temp gauge to spare myself head damage.
I got it home and pulled the head off of it and saw that the head gasket looked kind of worn oddly. I didnt use toyota OE gaskets and thought it was a problem with it being a felblow gasket. While i was there i noticed it looked like the block had a hairline crack down the right hand side between 3 of the head bolt holes. I might have missed it before or maybe it happened after the fact, either way i pulled it and replaced it.
I did another full build on the engine using only OEM parts this time and dropped the motor back in today. Low and behold, same damn problem as what i had before. Pouring white smoke and drained the radiator. I pulled the plugs and did a compression test and all cylinders are showing between 145 and 150psi. I also pressurized the cooling system up to 15lbs and it held for 5 minutes with no fluxuation. My thoughts are a crack in the head but it was pressure tested before i reinstalled it. The block was decked at a machine shop that i trust so i feel like if it was a block problem, they would have caught it. All i can figure is the head has a crack that is only showing up when the truck is warm but i am not sure.

I have had a buddy mention maybe the throttle body is cracked and leaking coolant into the intake plenum and that nissans used to have that problem. Anyone else heard of that? Any thoughts at all???

 

[3_puppies]

the machine shop should have NDT'd the head before doing any work on it. Any crack should have been discovered. I missed it in the above, did you replace the head and this is #2?

easy to check the coolant lines going to the intake. just loop them together, bypassing the intake, and see if it still happens.

only use Toyota gasket while still available, and re-torque.

 

[RocketCityCrzrs]

I don't think I did mention it, but yes the machine shop pressure tested the head at this assembly and the prior. Both times they said the head looked fine. After this incident I discussed with the owner over there, who I've known for a few years,and he did the work himself while I was in the shop and showed me the pressure numbers.
All I can think is maybe it is something that is presenting itself after the head is hot which is why it that's fine cold....

The intake lines I will certainly check, I was really just curious as to whether anyone has ever heard of that causing this problem

 

[Michael Hanson]

Hi, Did you torque the head down with a good torque wrench according to the service manual ? Did you re-tap and clean the block threads before reinstalling ? With dirty threads it's hard to get the proper settings . Mike

 

[FJACS]

Any chance of a massive leak in the oil cooler?

 

[RocketCityCrzrs]

I did have the block cleaned and decked before installation. I used new head bolts just to be safe, and torqued them to FSM specifications using the same torque wrench I have used for years. The only thing I sis different was remove the vacuum pump bracket on the left hand side of the engine. It had bolts that were about an inch longer so I replaced them with the standard length just like the others. I've read of a lot of folks doing the same so it shouldn't be an issue.

 

[RocketCityCrzrs]

Any chance of a massive leak in the oil cooler?

It is possible, but I would think that would leak coolant into the oil. The oil is clean and not milky at all nor has it increased the level on the dipstick

 

[OSS]

Examine the spark plugs or get a cheap bore scope and examine each cylinder while the head is still on. Try to derermine which cylinder is getting the coolant. My guess is theres a crack somewhere that didnt show up during the pressure test. Definitely retorque the headbolts (back off 1/4 then torque to spec) just to rule that out.

 

[FJACS]

If the oil is clean I guess that means coolant straight to combustion. Sorry for your luck on this.

 

[RocketCityCrzrs]

Examine the spark plugs or get a cheap bore scope and examine each cylinder while the head is still on. Try to derermine which cylinder is getting the coolant. My guess is theres a crack somewhere that didnt show up during the pressure test. Definitely retorque the headbolts (back off 1/4 then torque to spec) just to rule that out.

Well I did something similar. I pulled each of the plugs and put 10lbs pressure on the radiator. I used my inspection cam in each cylinder and none had coolant. Another strange mystery which makes think it might be heat related

 

[RocketCityCrzrs]

Fjacs, yep thoughts too. I am hoping intake but realistically I know better

 

[3_puppies]

is preasure testing NDT? I have heads magnafluxed or similar

 

[RocketCityCrzrs]

Yes, did NDT and then bolted head to a platform and presurrized the chamber through the plug hole

 

[LAMBCRUSHER]

Any updates? I’m chasing a slow loss of coolant...

 

[RocketCityCrzrs]

Yep, ended up being the throttle body warming lines. Bypassed them and no more issue

 

[LAMBCRUSHER]

Perfect! Thank you!

 

[RocketCityCrzrs]

Sure thing Man, I should have already posted back

 

[SteveH]

Yep, ended up being the throttle body warming lines. Bypassed them and no more issue

So, was the intake casting (through which this coolant passes) corroded thorough, allowing coolant from these lines to go into the intake stream?

 

[RocketCityCrzrs]

Yep, years of corrosion finally let coolant seep into the throttle body and through the intake into the firing chamber. I just bypassed the lines into the TB.

 

[LAMBCRUSHER]

bypassed my ISCV and TB yesterday. might just be the car-wash effect, but it seemed to idle more smoothly. hopefully my water stays put now, too. Thanks, TEAM!