Singing the precup blues (1 Viewer)

[Gengis]

[/ATTACH]

Why:
Ok, the head was done not longer than 30K km back and the precups were replaced because the old ones were slightly cracked.
They actually looked ok, but some I could remove with a bit of force and others had to be punched via the plug hole. Two of the new one's could be tapped in with my copper hammer and the other two had to be pressed in. One ( not the current offender) stood proud and had to be skimmed with the head.

Now, without any warning at all, number 4 drops on me, in a very inconvient ( expensive) location, but that's not your problem.

I
SO,did i buy a set of cheap knock-offs? I agree they were not from Toyota and had no brand name.
Any other reason for this and things to look out for and correct when and if I rebuild.

By the way, all the other precups are lose and with hairline cracks but seem to be functioning.
How many times can new precups be fitted ??? In other words are the holes in the head streatched, and could this be fixed??
Is there a good aftermarket magic bullet which will cure this problem once and for all.

G.

 

[cruisedeisel]

That sucks! Been there done that. Any internal parts is always straight to the toyota dealer. Time for a new engine

 

[ozcrusier]

Sorry to see the carnage in your engine but I have to ask was this engine turbo charged or normally aspired. Not sure if the engine needs replacing but defiantly needs rebuilding.

 

[gerg]

Very sorry man to see that. Nasty. I might be off but that precup looks melted a bit in the middle. Ive not seen a pre cup break in that fashion. Most have cracks that propagate and break large chunks off rather than fragment like that. It looks very weird to me. Put a magnet on that cup and see if its steel or low grade stainless. If it is, it would not handle a bad injector.

 

[OGBeno]

Wow. That is terrible.

 

[mongoose2231]

Damn, I was gonna skip on them when I rebuilt my engine. Glad I replaced them when I did. All of mine were cracked...

 

[ozwallaby]

As Gerg says things look melted.... I'm thinking (badly) leaking injector or very low quality precup...

Did you actually see the condition of the head/precups just before it was fitted to motor since my other thought is 2nd hand cup in number 4 in the rebuild, since you say the others look ok apart from the almost mandatory cracks......

 

[gerg]

That's a good point. Ive pulled cups that were only a few yrs old and they looked so good I was tempted to use them, but the consequences are so bad I can never trust them. I always use new. I get my cups from Roodogs. Always high quality and like I said, after a few years they look pristine.

I was thinking it looks like it might have been cast as opposed to machined? Almost looks like it crumbled sort of as well as melted. Could be a combo of bad part and bad injector? Did you check it with a magnet? Its not easy to melt stainless steel no matter if the injector is bad or not.

 

[Gengis]

What happened about 30K back was that i learned all about TTY head bolts from the forum, and realised that i had reused mine in the first rebuild about 70K back ( did not even know about precups then). So i whiped the head off just before a 5K trip around southern Africa and did the head up with a skim and new precups and an multilayer metal gasket and new bolts and all has been well since then.
I did the injectors about 4K back because she was starting to smoke a bit and the chap told me they were actually not too bad and the smoking continued, so i had the pump done and all has been very good for the last 3K.
We had absolutly no warning about this one, she had been humming away like Charlies Aunt and we were about 1.5 k into a trip, temp good, starting good, no smoke at all. And then suddenly at about 90kph aon a nice flat road all hell broke loose.
The only clue i can give is that we do run at about 3000rpm for extended periods 3 to 4 hours a lot, but again withing temp and smoke norms.

now doing some costing homework.
G

 

[gerg]

New piston and rings and a new head I would think would be what your looking at. Might get away with just a hone on the cylinder if its in spec. I did this very same thing for a dropped exhaust valve seat which is rarely if ever replaced, but can cause exactly the same carnage. I wouldn't trust the head unless your in a real pinch and would only use it till you replaced it later.

Sadly it might be a good idea to get a good running 3B and swap it as pulling and engine is easier for me than rebuilding one and takes less skill if your away from home and rebuild your poor engine later if you want.

 

[Gengis]

So, the pre-cup story.
Why are all the precups lose?
Did they shrink or did the holes in the head expand?
As mentionrd they were not toy origionals, but the others still look good ( except they are not tight).

I did the magnet trick and they all stick to a really strong magnet, but only just. if i shake it, the cup falls off. A similar size steel bolt has to be slid off. Should they have just a weeny bit of ion in them, or not at all.

I can't find a specification for the diameter of the precup recess in the head. Can anyone help on this one.

G

 

[cruisedeisel]

New piston and rings and a new head I would think would be what your looking at. Might get away with just a hone on the cylinder if its in spec. I did this very same thing for a dropped exhaust valve seat which is rarely if ever replaced, but can cause exactly the same carnage. I wouldn't trust the head unless your in a real pinch and would only use it till you replaced it later.

Sadly it might be a good idea to get a good running 3B and swap it as pulling and engine is easier for me than rebuilding one and takes less skill if your away from home and rebuild your poor engine later if you want.

I would do the same in this situation. Find a 3B and swap it. Way easier and cheaper than a full rebuild.

 

[gerg]

So that wee bit of magnetization sounds like stainless to me. If the head recess is cleaned out properly they do get a bit of wiggle in their spots, but once the head is bolted on they are stuck fast. So that still doesn't rule out a casting defect or a bad injector but I've never seen a bad injector do that to a precup. Could you have sucked in some foreign debris? Just throwing out guesses. I'm running out if ideas sorry. I still don't understand that small area that looks melted and how it appears to have crumbled as opposed to cracked in half which most look like. When they crack in half the crack is clean through both sides of the port and is well defined. Yours is by far the strangest I've seen.
g

 

[Gengis]

Dankie Boet

I am going to mark the injectors and take them for a test but not tell the technition what i am looking for. Be interesting to see how injector on this particular cylinder preforms.
From a damage point of view:
Block: If the conrod is not bent, then a rebore and a new set of pistons. ( or a new liner and just one piston) .

Head: It's a mark II b engine and i can't see any valve seat inserts// Is it possible that the seat is cut directly into the cast iron head??? Or do i need new glasses as well.
2 new valves
4 new Toyota precups
Seats replaced or recut
Check the rockers carfully as they must have taken some strain. replace if necessary.

New bearing shells, just because I'm already in there
Gasket set
Head bolt set ( Mark II, post 1988, has TTY).

Also, a shortage of 3B's in South Africa, so yes, it looks like a rebuild is in my future.
G

 

[tmarx]

Sorry man !

 

[cruisedeisel]

Testing the injectors is a good call. Find the source of the problem. The bottom end doesn't look like it took it too hard. When my precup fell it damaged the cylinder liner so I had to pull the cylinder sleeves or get a new engine. I went 2nd hand in the end. Best of luck and always use OEM.

 

[Gengis]

OK, so I am busy weighing up the rebuilding process.
Firstly, the engine already has liners inserted allowing for standard pistons. Will the liners take a rebore to the 1st oversize?? and is this a good idea. This engine is not "wheeled", does not tow and does not have a turbo fitted.
I have a question on the protrusion of the pre cups, but I'll do a new thread on that as it could get interesting.

G

 

[Gengis]

OK, so I now have the results of the injector tests.
No smoking gun, unfortunately, BUT, they are all down on their break pressure with a really crap atomisation and no ability to get them to "Chatter". I called Bull s*** so they took me into the back , hooked up all the injectors and , yes, the spray pattern on all of them was crap, a stream in one case. The only saving grace was that none of them dripped. The man said that this was definately the cause of my problems???

I'm not so sure, because I would have expected other warning signs, like low on power and smoking.


Can a bad spray pattern destroy the precups without any pre warning, is the question.

Please chime in.

 

[Vossie]

i tend to agree with you. surely there would have been some sign of bad injectors? like smoking

but then again, strange things can happen. it could be a combination of factors lining up to give you this unfortunate outcome

 

[RufusTheDufus]

Do you have any more photos of the precup area on the block in the bad cylinder? I'm looking at the grove the precup wore into the top of the liner.

It looks like that precup had been cracked for quite a while and wore through the head gasket? Is the block worn there as well? Hard to see in this photo.