SD25 block I overheated

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

SD25 block I overheated

#1

Post by waynosworld » 1 year ago

I have a question to ask you about my SD25 block I overheated several years ago that has been sitting in storage.
A little back story first, I bought the truck that had this engine from a guy north of Bremerton WA just across a floating bridge, he lost the transmission counter shaft bearing and it started just fine, so I bought it, I fixed the transmission bearing and then put the engine in my red 720 dually, the guy had used it to run veggie oil and a heater to get the oil hot before entering the injection pump, he had a 1 gallon tank under the hood to start it and clean the pump out of veggie oil before shutting it down.
So I overheated the engine one night, the night my dash lights decided not to work, I noticed steam coming out from the hood vents when I left the freeway and came to a stop, I added water to it for the 3 miles it took to get it home, it did spit out coolant a couple times but I never shut it off, I fixed the hose just in back of the injection pump and called it good.
So the next time I drove it it started alright, not great but alright, but it smoked and smelled funny, a really strange smell, it took at least 15 minutes for it to mostly quit smoking, I drove it this way for quite a while, basically it had no more power than an SD22, now I am comparing the power to my silver 720 with a great running SD22 and my 521 kingcab with a great running SD25 without a turbocharger, I finally gave up on this engine because I feared I had cracked the head between the valves, I was not loosing coolant at any point after the engine overheated and I had fixed the coolant hose, so I do not believe it was steam coming out the exhaust, the engine was gutless.
One day before I gave up on the engine I bought new glow plugs and installed them, it started great and didn't smoke at all, I was amazed, but the next day it would not start, so I tried removing a glow plug and could not get it out, it was sorta loose but it would not come out, so I grabbed it with a pair of vice grips and i finally got it out, the end of it had blown up like a balloon, I was very lucky to get them all out, they all had blown up like a balloon and didn't work any more, so I put the old ones back in and it was back to smoking real bad and smelling funny.
Now I finally rolled this engine out of storage after several years and pulled the head yesterday, except for black soot on the top of the pistons everything looks great/new, the head is fine, there are no cracks, the pistons look almost new, they have a 02US marking on them, they look very tight in the bores.
Does this sound like a block issue or an injection pump issue?
Can overheating the block hurt the injection pump as it didn't smoke like that until I overheated the engine?
Could the rings have been hurt enough to make it smoke but not loose much compression?
I look at this engine and how new it looks except for the soot and don't want to pull it apart any farther.
I suspect the injection pump needs rebuilt because of the veggie oil being put threw it, but it didn't smoke/smell funny till I overheated it.
Does anyone have an opinion on this, I just don't get how it could be the injection pump after I overheated the engine, but they do share oil.
Here are a couple photos of how it smoked and the color of the smoke.
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image.png (628.27 KiB) Viewed 1126 times
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: SD25 block I overheated

#2

Post by waynosworld » 1 year ago

I have another thread about this on another forum, I would have posted it here but it is a real pain to post photos to this forum right now, it will load the photos but it doesn't give me the option to place the photo inline, what I had to do on the first post was copy the image address from another forum post, then paste it to the field, then it loaded and allowed me to place the photo inline, I could not load the photo from my computer so I have to post the photos to another forum to post them here.

Here is the post I wrote about this block this evening, the link below should take you straight to the post.

https://www.nwdatsuns.com/viewtopic.php?p=73068#p73068
I know the voices are not real,
but they have some really good ideas.

TheDieseliminator
Posts: 205
Joined: 14 years ago
Location: Florence, AZ
Contact:

Re: SD25 block I overheated

#3

Post by TheDieseliminator » 1 year ago

Would you be willing to sell that sd25 engine? I've been looking for one for awhile.
1982 Datsun Maxima diesel wagon w/ 228k miles
*occasional daily driver*

1982 Datsun Maxima diesel sedan w/ 252k miles
*now off the road as a parts car and sent to the yard :( *

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: SD25 block I overheated

#4

Post by waynosworld » 1 year ago

If you have read the latest in that thread I put the link to you would know that it has an issue, #3 cylinder came up 1mm short of flush with the deck like the other 3 cylinders did, I had some SD22 rods I compared to the SD25 rod, they are the same length and width, but they are slightly different in size and weight even though I think if I used 4 SD22 rods I believe it may work, well it turned out that #3 rod is bent, you can see it in this photo below, that is an SD22 rod in the background.
image.png
image.png (1.36 MiB) Viewed 1114 times
I was going to visit a forklift place tomorrow or the next day that says they carry Nissan forklift parts, I am hoping to find one SD25 rod.
I am thinking the piston coming up 1mm short may have been why it was smoking so bad or maybe contributed to the smoke as 1mm is a lot and it likely lowered the compression in that cylinder, maybe a lot, I could not tell it had a bent rod though, fact is that cylinder bearing was the best one of all the bearings.

Where are you located TheDieseliminator?
I know the voices are not real,
but they have some really good ideas.

TheDieseliminator
Posts: 205
Joined: 14 years ago
Location: Florence, AZ
Contact:

Re: SD25 block I overheated

#5

Post by TheDieseliminator » 1 year ago

I apologize as I didn't get to go through this whole thread, but very good find on the bent rod. I'd still be interested in the engine with that set back of the rod. Nissan forklift dealer should be able to come through on finding something. I definitely do like your 521 pickup and 720 dually even more! I have a dually rear myself I want to put into a truck, as well as a handful of the factory dually wheels that came on these full floating rear ends. I am located in Florence, Arizona. Thanks.
1982 Datsun Maxima diesel wagon w/ 228k miles
*occasional daily driver*

1982 Datsun Maxima diesel sedan w/ 252k miles
*now off the road as a parts car and sent to the yard :( *

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: SD25 block I overheated

#6

Post by waynosworld » 1 year ago

If you have a Nissan dually axle you need to keep in mind that the Nissan C200 dually axle is made for gas engines, specifically the Z24 engine with a rpm range way higher than a SD series engine, the best gearing it has for freeway driving is 4.1 gears(411s), these gears are not made for our diesel engines, I drive 75mph on the freeway, even with 3.5 gears I am at 3000rpms in 5th gear, that would likely be past the redline for an SD series engine with 4.1 gears in the rear, and I have never seen a Nissan dually axle with 4.1 gears, but the 1985/86 Nissan 720 4wd trucks have a C200 rear axle and the 4.1 carrier inside that will fit in the C200 dually axle, but again unless you have a 4wd diesel powered truck with giant wheels/tires it just isn't a good axle for a SD series diesel engine, there may be aftermarket gears for the C200 more freeway orientated but I have never heard of anyone with them, but I have not been looking or asking about it either.

My 720 is a dually cheat, it has a H190 rear axle with adapters that use the Nissan dually rims from their dually axles, that H190 has 3.3 gears in it, I would never try to haul weight with them adapters on the truck, but it is a great truck to haul a trailer or tow another truck home, when I need to use that truck to haul anything I put aftermarket dually rims on it, here below is a photo of the truck with a flatbed/tommylift and the aftermarket rims on it
image.png
image.png (1.16 MiB) Viewed 1100 times
I didn't find any rods today, the place I went to was not there anymore, so I called their number and that guy was in Spokane WA, tomorrow morning I plan to try a few places in Portland OR and then the Nissan dealer if I have to.
All the rods I have found on the internet seem to be SD22 or aftermarket rods even though they say they are for the SD25 also, I have an SD22 block in storage that I will never use that I could take the rods out of, but the SD25 rods are beefier for a reason, so that would be a last resort, they are the same but lighter, so if I use one rod I have to use all 4 SD22 rods as the SD25 rods are way heavier weight wise, no way I could only use one rod as the rotating assembly would not be balanced anymore.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: SD25 block I overheated

#7

Post by waynosworld » 1 year ago

I had no luck today, the Nissan dealer was a complete waste of time, it took that guy 15 minutes to find a reference to a Nissan truck with an SD25 diesel engine in it.
The forklift place was not much better, they found one rod from Nissan for $1200.00, I am not sure if it was specifically for an SD25 or if was for several engines(SD22, SD25, TD27, ect.), since I have 4 SD25 engines including this one I think I may put this one mostly back together and keep it for parts for the other 3 engines, I could never even find an SD25 head for what I could sell this engine for complete.
I have not given up yet, but I am not likely going to actively drive around looking anymore as I do not need an engine to fix any of my trucks right now.

I did find this place in the link below, has anyone ever dealt with this company before?
https://partswecan.com/product/connecti ... ine-parts/
I know the voices are not real,
but they have some really good ideas.

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: SD25 block I overheated

#8

Post by plenzen » 11 months ago

Just reading this thread Wayne. ( I've been preoccupied looking after a 5 soon to be 6 yr old and at 67 years its a bit of a challenge)
In any event.
Just viewed the link you posted for engine parts as well. $40.00 for a connecting rod seems like a pretty good deal. I have never dealt with them. Would be interested to see what the quality is of said parts. Cant beat the price for sure.

You may want to try contacting some of the Nissan Dealers in Canada as the SD 25s mostly came here. I'm not suggesting they would have a con rod sitting on the shelf, but they at least acknowledge their existence. They were in all the D21 diesels that were sold here. Another place may be OZ as they had lots of them go there. I think there may even be a few members on here from "Down Under". If you could reach out to one of those guys there may be a few of them lying in a bone yard someplace.
Check the lower mainland of Vancouver B.C. as well. Bansal And Sons comes to mind. They are on the south end of Vancouver and have a lot of diesel ????? " Stuff" lying in their yard. A long shot.
( These guys : https://411.ca/business/profile/12558017 )

If your still looking for a con rod, and if you want me to, I can call the dealer I use here in Calgary and ask him. I'll use the VIN from my truck to see if he can find one. The Ausie parts guy there is pretty accommodating.
Not sure of the vintage of your SD25 but pretty sure they were all the same through the years. Fuel delivery systems varied but the engines I think were all the same.

As to your smoking overheated SD 25, I think perhaps when it got hot the rings lost all their tension and thus the drop in compression and the smoking. Smoke looks more like oil smoke than fuel as it appears to be a slight bit blue.
The rod damage almost looks like Hydro lock damage. Might of had a bit of water in there after the overnight soak ( no pun intended ) and when it "hit" the next day it likely squashed it a bit. That is a guess on my part, but I have seen "hydro locked" rods before, however they looked a lot worse than that one you posted the picture of, the ones I saw happened when the engine ingested water and a pretty high RPM. ( marine application )

P
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: SD25 block I overheated

#9

Post by waynosworld » 11 months ago

The truck the engine was in was a 1985 Nissan 720 imported from Canada I believe, it had a weird wiring harness, it was also set up to run Veggie oil when I bought it, I drained around 8 gallons of it out of the tank, it had a small one gallon diesel tank in the engine compartment.
I don't believe I was the one that bent the rod, but I did over heat it, and it smoked after that event.
I have a SD22 parts engine in the shed that I believe I can use the rods out of, that SD22 engine will never run again as it is an SD22 that I have no interest in, the thing I worry about is that the rods may be the same in every way except weight, SD22 rods look light duty compared to these SD25 rods, but in the end I do not need this engine to power a vehicle, I have engines in both trucks now and one SD25 crate engine in storage as a back up, so unless I were to sell this block to someone which I doubt will happen because I doubt I could get out of it what the head alone is worth.
The cylinders are not terribly scratched up, but I was told the pistons were beat up pretty bad, I don't see the point in rebuilding it myself, so it is a parts engine.
I have actually tried contacting wrecking yards in Australia about other more important parts to me, I could not get any of them to respond, I suspect it is because I am inquiring from the USA, I have a few friends over there I use when it is very important, but this is not even on that list.
Since I have been turbocharging all my engines I suspect having a parts engine is a good idea, I don't beat on these engines, but it really depends on what one would describe as beating on them, with the turbocharger I use the top 3rd of the pedal and I rarely see more than 6psi boost except when accelerating, but without the turbocharger I was almost floored on the freeway most the time, and my EGTs were way above a 1000 degrees all the time, now with the turbocharger I rarely see over 900 degrees, only on long uphill grades do I see it over a 1000 degrees, so in my opinion I am way better off with the turbocharger, I average 4 to 6psi on the freeway, but it is boost and I have no idea what boost does long term to these engines.
Thankyou for responding.
I know the voices are not real,
but they have some really good ideas.

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