Hi all, I am new to this forum and am wanting to find out if all 3b precups are the same. I have a 1984 3b and a head from a 1989 3b. The engine had been rebuilt and new head put on about 60k miles ago. I recently had a precup break and ruin the #1 piston. All of the precups look to be on the verge of breaking as cracks go all the way through to inside of cup. The precups wiggle just a bit and I don't know if this is normal. Before this catastophic failure the engine was hard starting at cold temps and smoked badly until warmed up. Injectors good, glow system good. The previous owner said it always started right up even down to -20f until he put the new head on. He compared the new head with the old head and everything measured the same but he said he didnt compare the combustion chambers and after what had just happend to the engine it dawned on him that the precups might be different and would explain poor starting and premature precup failure. He put new sleaves, pistons and chrome rings in and even after many thousands of miles the compression is only 360 or so. Any info on precups would be greatly appreciated. Thanks.
3b precup question
- Thread starter DelNorteDiesel
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cruiser_guy
Out of Africa / North Africa
All precups I have ever seen (and I've taken a few heads off of 3B's) are cracked. Some are loose. I've also had a precup drop into a cylinder and smash the piston. It happens but I don't think it is a common occurrence. I my case I had driven the truck for over 15 years and 200,000 kms before this happened and there was NO work done on the engine prior to that.
Hard starting is often a result of poor compression which it appears you already know. I'd be questioning how well the work was done when the sleeves were installed and pistons replaced. Did it get bored correctly? Are the rings good? Are the rings installed the right way around?
Hard starting is often a result of poor compression which it appears you already know. I'd be questioning how well the work was done when the sleeves were installed and pistons replaced. Did it get bored correctly? Are the rings good? Are the rings installed the right way around?
- Thread starter
- #3
Thanks Cruiserguy
Thanks for your response. I know the guy who did the work on the engine and he is very meticulas and skilled and I believe his work was good. The question I am still after is if there is any difference in any of the precups from an 84 b engine and an 89 b engine. The head he bought was a new head that was kept as spare part in a mine in Canada. It has the extra coolant ports to minimize cracking from overheating. We think that if there is any difference in the shape or volume of the precombustion chamber then it may have the wrong precups. He bought the precups that were called for for the 84 3b engine but the 89 head may have a different precup. This is the one thing that he did not compare with the old head. If there is a dealer or some else that would be able to check if there is a difference that would also be great info. Thanks again for your help. P.S. I did not know the rings have a specific orientation, I will ask him about that and look at the manual.
Thanks for your response. I know the guy who did the work on the engine and he is very meticulas and skilled and I believe his work was good. The question I am still after is if there is any difference in any of the precups from an 84 b engine and an 89 b engine. The head he bought was a new head that was kept as spare part in a mine in Canada. It has the extra coolant ports to minimize cracking from overheating. We think that if there is any difference in the shape or volume of the precombustion chamber then it may have the wrong precups. He bought the precups that were called for for the 84 3b engine but the 89 head may have a different precup. This is the one thing that he did not compare with the old head. If there is a dealer or some else that would be able to check if there is a difference that would also be great info. Thanks again for your help. P.S. I did not know the rings have a specific orientation, I will ask him about that and look at the manual.
According to toyodiy they are different part numbers between pre 1987 and post 1987. Pre 87 is 11106-58010. Post 1987 is 11106-58020. No idea if they are interchangeable or any other differences. 
- Thread starter
- #5
Thanks ff lc freak, I will look into those part numbers and see if I can talk to someone who can tell me if they are different. This forum and you guys are great.
I think they ar diffrent and i would not take chances on this one !!
- Thread starter
- #7
Well, I talked with someone at 4wheel auto he said the precups were the same. If anyone has confirmation on this or a contradiction that would be really good information. Thanks again for your contributions. Also if anyone knows if the prechamber volume or shape for the different year heads is different that would be helpful (84 and 89).
crushers
post ho
89 3BII
84 3B coarse gear
completely different heads
i have never read of anyone doing a volume test of any precups.
360 is a terrible reading, i know some might think it is acceptable since recommended rebuild is 280 but considering 425 is preferred, not good.
i would maybe suspect wrong thickness of head gasket was installed when the head was replaced. either way, you will be pulling the head.
this is assuming it is 360 across the board and not just the damaged cylinder.
84 3B coarse gear
completely different heads
i have never read of anyone doing a volume test of any precups.
360 is a terrible reading, i know some might think it is acceptable since recommended rebuild is 280 but considering 425 is preferred, not good.
i would maybe suspect wrong thickness of head gasket was installed when the head was replaced. either way, you will be pulling the head.
this is assuming it is 360 across the board and not just the damaged cylinder.
Keep in mind that compression will read lower at altitude. Del Norte is near 8000 feet above sea level.
Using the conversion factor of 0.800 for 7500 feet above sea level, his compression is closer to 450 PSI (450x.800 = 360).
According to toyodiy they are different part numbers between pre 1987 and post 1987. Pre 87 is 11106-58010. Post 1987 is 11106-58020. No idea if they are interchangeable or any other differences.
My information supports the 4wheel auto advice.
11106-58010 and 11106-58020 appear to be interchangeable.
I read that 58020 superseded 58010 and is now the part number to order for precup replacements for any 3B engine from Aug 1980 (which was the introduction of the 3B) right through to August 1999.
I think Aug 88 was when cylinder liners disappeared on the 3B...
So the old block (with the liners) would probably have dictated that an old head gasket were used...
Not sure whether this is relevant..........
So the old block (with the liners) would probably have dictated that an old head gasket were used...
Not sure whether this is relevant..........
- Thread starter
- #13
Thanks for the responses, good to get confirmation on the precups being the same. I can only assume that means the volume in the prechambers would be the same as well. The reason the previous owner put this head on is that it has the extra cooling ports to keep it cooler so less likely to crack. He had precicely measured everything else against the old head and it measured the same except he did not measure the volume of the prechambers. His thought if the prechambers are the same and the head gasket is the same ( I read somewhere on here that there is only one thickness for the head gaskets) is that he honed the cylinders too fine and he used chrome rings so maybe when it is cold the rings dont seat well enough to start good. I am hopefull I can just have the sleeves rehoned and put new rings in (not chrome) exept the number one sleeve is damaged and will need to be replaced. Any advice on this would be really helpfull as I have never had to bebuild an engine and know quite little about it though, thanks to this forum, that is changing a bit. Now I am off to pull out the block so I can take it to the machine shop next friday. Thanks again so much for all of the help. And wow, I did not know that the 3b was produced until 99.
Shop your machinists. Make sure they understand diesel engines and make sure they are willing to actually look at the clearances in the factory engine manual.
Also, that 360 PSI number is as good as it should get at your altitude (if the compression test was administered at your altitude).
Also, that 360 PSI number is as good as it should get at your altitude (if the compression test was administered at your altitude).
- Thread starter
- #15
ok slower than u, thanks for your advice. The machinist i will use has extensive knowledge of diesels as we have alot of agriculture here in the San louis Valley. He seems very good and I do have the factory service manuel to provide to him. I do have another question about precups. I talked to 4wheel auto and he said they have the stainless steel precups at I think 75$ each. I dont know if they are better and wont crack or what. What are the old cups made of? If they can handle the heat better and wont crack and fail that would be so worth it. Anyone with the skinny on this. I read a thread that someone asked this question but no one answered it. Thanks
I bought the stainless steel precups from roodogs. I think the total with shipping to the US was only $140ish. Might be worth it to shop around.
As far as stainless not cracking, I would say they all crack at some point. Due to the dissimilar metals, the heating and cooling cycles will eventually have their way with the precups. Just my opinion.
As far as stainless not cracking, I would say they all crack at some point. Due to the dissimilar metals, the heating and cooling cycles will eventually have their way with the precups. Just my opinion.
- Thread starter
- #17
Thanks again FF LC FREAK. Do you think the stainless precups have less chance of fully coming apart? Wish this precup problem could be really fixed, makes me nervous you know. These cups only went about 60k miles before they failed. Thats not too good especially for a diesel. What about milling out the cup chamber a little and pressing in a seat that would fit the cup better. Maybe their is a more suitable material for that interface that could absorb some of the movement from the different rates of expansion. I will talk to the machine shop and see what they think. I plan on adding a innercooler so that should help a little if failure is really due to high temps. My head was not cracked so I am not sure if he heat ever got too much. I have an egt guage and try to keep it below 1150f. Any thoughts?
cruiser_guy
Out of Africa / North Africa
They all crack. You just live with it. Generally they do not crack and fall into the cylinder (though sometimes that happens, I know from experience).
