Datsun Roadster Forum-311s.org

Hi everyone,

I recently acquired a '70 1600 that is in really great shape aside from the motor being seized. From what I was told, the motor was newly rebuilt prior to it sitting for 5 or so years.

After some research online, I created a mixture of ATF, PB Blaster, diesel, and sea foam and filled the engine through the spark plug holes. I've been rocking the crank each day to try to loosen things (not too much pressure because I don't want to break anything).

Has anyone had luck freeing one of these motors and can provide tips?

Thanks,
Matt

Welcome Matt:
The question is why it is seized, is it just from sitting, or did it seize up after running for a while? If it seized while running, that is not good, and I would go no further with the efforts other than to remove it and tear it down. If seized from sitting, I think you are doing the right things, but that should have loosened it up pretty well. If still too much resistance, then again, I would consider tearing it down rather than risk damage that is expensive to repair.

Thanks for the quick reply!

I was told it's seized from sitting, but that's third-hand information at best. Something curious that I've found is that the 4-speed manual feels like it's going into gear at the shifter, but I can still spin the driveshaft (via turning the rear wheels) when it's supposedly in gear. The engine doesn't spin (since it's seized) and I can't feel any difference in resistance at the wheels.

Can you spin the wheels like that in each or other gears? If that is the case, and the engine is seized, then maybe the input shaft on Transmission is broken? That is very weird indeed. I happen to have an R16 block that is seized (Rod I think) and I actually use it to hold the transmission input shaft still while I torque the large nut at the back to 140 foot pounds. EDIT: Which takes the differential out of the equation - the source of your normal operation!
Tom

I think what you are describing with the rear wheels is normal i.e if the driveshaft is locked, yes, the differential still allows the wheels to rotate since it most likely is not a limited slip diff.

Put the trans in neutral and a 27mm socket on the front of the crank. If you can't turn the crank at all, it is seized.

When this happens, 99% of the time the cylinders have rusted and sieze the rings. You will break them if forced. If the cylinders are rusted, the rings won't ever seal.

Best, jt

^ D'Oh, yes, the differential is supposed to do that. My brain seized in thinking too hard on that!

If the motor is fresh, I strongly suggest disassembly of the complete motor. It should come apart with little trouble. You might need to replace the rings along with many of the gaskets.

If you don't have time or experience with going through a motor, try to find a used motor and rebuild that motor over time.

If it's the blue one from MD, that motor was stuck when it was in my garage years ago. It's been stuck for at least 10 years.

Basic question but sometimes overlooked .
Have you removed the belt off the water pump and tried to spin the motor after jacking the car's rear and rotating the rear wheels by hand while the trans is in gear?
I have had motors that appear to be locked only to discover the pump seized up instead.
Rick

I learned all my wrenching from ROadkill. ROadkill Garage and Dirt Every Day



Driveway Rescue of a 1950 Jeep CJ-3A! - Dirt Every Day Ep. 33
at 6:00 into the video, they try to free a seized engine
All of the above advice from members is spot on.

Viney

Update: I worked on freeing the rear passenger brake drum last night since it got itself locked up. While I was down there I tried spinning the wheels again. I was mistaken (must not have actually been in gear?). Everything regarding the trans operates as expected. Sorry for the false alarm. Only neutral spins the driveshaft and that's to be expected.

@datsun1500 That's the one! Mark, I presume? I guess 3rd-hand info isn't the most reliable. I believe Dave told me 5 years. He gave me your number, but I didn't want to bother you before I gave it my best shot.

I'm just going to pull everything this weekend so I can tear her down and see what I'm dealing with.

@19692000survivor Yeah, the belt is loose. Thanks for the tip, though!

@vinechoy I've been watching a ton of Roadkill lately. It's really inspiring! Hadn't seen the one you linked to. I was really hoping I'd be that lucky haha

I bought a 1970 2000 back in 2007. It sat in a garage for 30 years and the motor was locked up from sitting. Every day for about 2 weeks, I would pour some ATF down in the cylinders and put a breaker bar with a cheater bar on the crankshaft bolt. after I was able to free up the motor, I continued with the ATF and turning it over by hand.

Funny story, I had put a bit too much in one cylinder before turning it over by hand, and It shot ATF out the spark plug hole. Hit my dad right in the mouth

I rolled the engine over a lot with the starter for a while with the plugs out to get everything as freed up as possible. Hooked everything back up, changed the oil, and the car started right up. It ran great! If it is truly just stuck from sitting, you shouldn't have anything to worry about. I hope it didn't seize up from another issue. I would at least pull the oil pan, and see if you can see any obvious signs of damage. Good luck with getting it going.

Cheers,
Wade

Haha I'm looking forward to hitting an unsuspecting friend in the face with some ATF.

What you describe is exactly what I'm hoping for, but I filled the combustion chamber up completely with my mixture so I could see if it was working. It's been nearly a week and the ATF seems to be at the same level. Were you having to top off the ATF over the 2 weeks?

It was so long ago, I can't remember how often we were adding ATF, but I remember adding a little bit multiple times while working on other areas of the car. I wouldn't think totally filling with your mixture would hurt anything, and get some torque on that crank bolt. Not too much though, a torqued off crank bolt is a bad bad thing... Find out what the torque spec is on that crank bolt, and try not to go over that. Can't remember if they are left hand thread or not. You're probably alright to put around 75-80 ftlbs on it. Are you able to look down the spark plug holes and see the cylinder wall condition? I do advise pulling the oil pan, and checking it out from underneath as well.

Anyone know the crank bolt torque spec?

I think it was some ridiculous spec, like 160lbs. I don't recall ever getting it that high with the engine in the car...