3b head gasket blown (1 Viewer)

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Sep 3, 2007
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after replacing it once because I'm an idiot and didn't notice a heater hose leaking, now i get to replace it for real... probably also because i'm an idiot.

anyway, my truck pukes coolant when pointing down hill, and there are bubbles in the overflow tank. I used a combustion gas tester to test the coolant so i'm pretty sure its HG time.

now, the question - why do i have to do this again?!?! I can think of only two things I did wrong:

#1 I used an aftermarket gasket instead of OEM

#2 One of the precups wasn't quite seated to spec. Spec protrusion is 0.05mm and one of mine was 0.10mm - I couldn't get it any tighter.

Are either of those a sure-fire "thats yer problem" thing?

Also, whats the p/n for a new head, and what does it come with? I don't know if installing valve seats and s*** is a DIY job or if I need the shop to do it? If I can buy a head with everything installed maybe I'll just swap heads at the same time......
 
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haha i knew i could count on you cruiser_guy to remind me to check for cracks... like you did last time :D

i'll have it checked. i'm going to keep hoping its just a blown up gasket tho :)
 
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brampton ont
the precup should be fine but I think your problem was the head gasket itself
was there plastic on the aftermarket head gasket? toyotas is all metal and one rubber o-ring
were the surfaces head and block clean? I wipe all gasket mating surfaces clean with break cleaner
A new head from toyota is $1000 just the head the numbers on here ive posted it twice if you caint find it ill post it again

man that sucks sorry to hear your woes, the heads a pain in the ass to remove
 
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.....#2 One of the precups wasn't quite seated to spec. Spec protrusion is 0.05mm and one of mine was 0.10mm - I couldn't get it any tighter............
I know you have seen John's posts (like this one) about "always machining heads after fitting new precups:

https://forum.ih8mud.com/diesel-tech-24-volts-systems/261040-coating-pre-cup.html#post4037495

So perhaps it was indeed the precup protrusion? (I don't know.)

:cheers:

PS. Maybe John (RaddCruisers) knows something we haven't yet learnt.

I think my B-engine manual lists a "range" for acceptable "precup protrusion" and I have a feeling that 0.10mm was at the upper limit (but not exceeding it).

But John seems to insist on "zero protrusion".
 
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well, I'm pretty sure it wasn't the precups. How am I so sure? I looked!

I had some free time tonight, so I completely disabled my truck in 1.5 hours flat. Having completed the One Man 3B Head Lift event in the previous olympics, I got clever this time and hoisted it off :D

Trying my hand at reading the gasket, correct me if I'm wrong:

The gasket was in fairly good shape, nothing alarming. My leak was pretty slow (maybe 2 pebble-sized bubbles per second) so I didn't expect to see the armor blown apart or anything. Looking at it, however, I'm guessing the #4 cylinder was blowing into the nearby passages - the formed rings on the gasket in that area seem to have deteriorated on the cylinder-side. My guess is this was due to a s***ty job cleaning the surfaces in that area, which I seem to recall not being very meticulous about. The head bolt between #3 and #4 was rusty (the others were oily, like I left them) and shows similar damage to the sealing ring.

Also, fun fact, it apparently takes more than 5000 miles for precups to crack - all of mine are still whole. But then, I keep it under 1250F.
IMG_4791-800.jpg
IMG_4795-800.jpg
IMG_4799-800.jpg
 
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holy s***, i need to tear this thing ALL the way down for magnafluxing?! thats a huge problem, as the valve steam seals are now unobtainium, I'd have to buy a full gasket set that has em in there. this is getting expensive, s***.
 
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You may not be able to see the cracks if you do not magnaflux the head. Are you sure the valve stem seals are unobtainium?
Yeah, almost a year ago now I replaced mine and tried to buy them from SOR - I bought the last 6 they had. Both Kay at SOR and myself tried to find a new supplier for the balance but no one has em anymore. The only way is to get them inside a gasket set, but I don't want aftermarket parts anymore. hmm.

What do you all think about dye penetrant testing? The internet seems to suggest its as-good as magnafluxing.
 
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There are a few types of allowable cracks in a cast iron head... if you're unsure, get it pressure tested at your local machine shop. Magna-fluxing will find cracks, but they may be acceptable for putting the head back into service... talk to your machinist.

The gasket surfaces must be totally clean and dry. You must not use a polishing wheel or surface conditioning disc on either the block or the head- think good old fashioned elbow grease and razor blades etc... to get things perfectly clean.

The bolt holes must be totally cleaned out and free of dirt and debris. Clean them with brake cleaner so that they are clean and dry all the way down.

Use new head bolts where you can, and lightly oil them at the threads and flange area before torquing into place. Torque in stages, even if you manual doesn't talk about it. The stages should not be too close together in value - maybe three stages would be a good idea.

If you installed new pre-cups, get the head machined. Don't be too cheap for your own good, it costs less to do it right once.

When you remove a head, use the reverse sequence from how it's tightened down. Do it in stages, do not fully loosen one bolt and then move on to the next - be nice, do it in stages, it's an expensive piece of metal you're dealing with.


~John
 
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There are a few types of allowable cracks in a cast iron head... if you're unsure, get it pressure tested at your local machine shop. Magna-fluxing will find cracks, but they may be acceptable for putting the head back into service... talk to your machinist.

The gasket surfaces must be totally clean and dry. You must not use a polishing wheel or surface conditioning disc on either the block or the head- think good old fashioned elbow grease and razor blades etc... to get things perfectly clean.

The bolt holes must be totally cleaned out and free of dirt and debris. Clean them with brake cleaner so that they are clean and dry all the way down.

Use new head bolts where you can, and lightly oil them at the threads and flange area before torquing into place. Torque in stages, even if you manual doesn't talk about it. The stages should not be too close together in value - maybe three stages would be a good idea.

If you installed new pre-cups, get the head machined. Don't be too cheap for your own good, it costs less to do it right once.

When you remove a head, use the reverse sequence from how it's tightened down. Do it in stages, do not fully loosen one bolt and then move on to the next - be nice, do it in stages, it's an expensive piece of metal you're dealing with.


~John
Thanks John, good info. And don't worry, I used the FSM pattern removing the bolts - every once in a while I do things right :D

I just spoke to a machine shop - dropping it off tonight for pressure testing and machining.
 
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I'm back home now where I have access to my FSMs so I thought I'd check to see how accurate my memory was.

Yes. I was right that my 1977 B-engine FSM allows as much as 0.10mm chamber protrusion:

Protrusion1977Bmanual.jpg

But the 1988 manual only allows half that amount:

1988protrusion.jpg

And the 1988 manual suggests dye as the FSM method of checking for cracks too:

Dye.jpg

:cheers:

PS. But I'm not disputing John/RaddCruisers advice. (I've always found it top-notch.)

(I'm just providing this for "background information purposes".)
Protrusion1977Bmanual.jpg
1988protrusion.jpg
Dye.jpg
 
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Oh man I feel for you. This happened to my 97 FZJ80 a few years ago, but mine had alot more damage.

Do you have a pic of the pre-cups before and after ? I've heard so much about these things but have yet to see one.
 
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crushers

post ho
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holy s***, wash out that poor old rad, no wonder it was puking out its guts.

what i find is funny is the dozens of 3B heads i have replaced, the number of head gasket/prechambers i have replaced and NEVER had to have the heads shaved.
i have yet to remove a head in the round about method. (installation 3 stage center out of course.)and i have yet to find a warped 3B head.

this is by no means to say that you shouldn't do as John is recommending, i am just saying...

as for the cracks, if you can not see them with your naked eye then they are not your problem. when a 3B head starts leaking into the combustion chamber it is from between the valves and the cracks are very visable...
 
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good news! no cracks! head is resurfaced, but I'm going out of town and will pick it up on Tues. OEM gasket is en route from 4wheelauto, who were awesome.

any tips for cleaning the block?
 

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