RTH! Messed up threads on block drain (1 Viewer)

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Yeah.. I'd be ABSOLUTELY certain that is BSPT before you go running a tap into the block. Meaning, if you don't know how to accurately measure thread diameter and pitch of the new OEM plug you need to have someone else do it.

If PO used a 1/4 tap the old plug should now compare pretty well to a 1/4PT fitting if you can find one to compare.
 
Yeah.. I'd be ABSOLUTELY certain that is BSPT before you go running a tap into the block. Meaning, if you don't know how to accurately measure thread diameter and pitch of the new OEM plug you need to have someone else do it.

If PO used a 1/4 tap the old plug should now compare pretty well to a 1/4PT fitting if you can find one to compare.


Just as an FYI, 1/4 inch NPT is 18 threads per inch, 1/4 inch BSPT is 19 threads per inch. So while you might be able to start a 1/4 NPT tap into a 1/4 BSPT hole, you won't be able to turn it in but about 1 turn before it starts to turn HARD. Now if the PO kept forcing the tap in to the hole, those threads would be ruined.
Here's a link to where to buy the correct BSPT tap.
McMaster-Carr
 
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I looked at the threads today with an inspection camera, and there doesnt seem to be any sign of cross threading. I assume the only reason the npt fitting will even start is because its close, and tapered. That rambling was just frustration and exhaustion coming out.

Its amazing how much info the Internet has, I've learned way more than I've ever wanted to know about pipe threads. Thank you Bloc for sparking my interest. I measured the new plug, outside diameter at threads is 13.818, and minor diameter is 12.5984, or a little less because the threads are sharper than my caliper.

1/4BSPP is 13.157 major, 11.445 minor diameter.

So maybe it isn't british pipe thread after all? I can't quite squeeze my calipers up to the block to measure that, but I might have a t gauge small enough at work.

Back to the plug. The specs are actually closer to 14x1.25mm

Also I don't have the little drain cock type fitting with the hose off the side on the side of my block, were those only on earlier 1fz's? Mine is a 97 since it wasn't previously stated. So many questions ugh:cry::censor:
 
My best guess from working as a machinist for years is that the first few threads in that hole has a burr on them. You can buy a 1/4 inch BSPT tap to just chase the threads, more then likely that will solve your problem. By the way 14MM X 1.25 has 20 threads per inch, and as i said above 1/4 NTP is 18 threads per inch and last BSPT is 19 threads per inch. So just count how many threads per inch is on your plug, that will tell you if it's MM, NTP or BSPT.
 
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I looked at the threads today with an inspection camera, and there doesnt seem to be any sign of cross threading. I assume the only reason the npt fitting will even start is because its close, and tapered. That rambling was just frustration and exhaustion coming out.

Its amazing how much info the Internet has, I've learned way more than I've ever wanted to know about pipe threads. Thank you Bloc for sparking my interest. I measured the new plug, outside diameter at threads is 13.818, and minor diameter is 12.5984, or a little less because the threads are sharper than my caliper.

1/4BSPP is 13.157 major, 11.445 minor diameter.

So maybe it isn't british pipe thread after all? I can't quite squeeze my calipers up to the block to measure that, but I might have a t gauge small enough at work.

Back to the plug. The specs are actually closer to 14x1.25mm

Also I don't have the little drain cock type fitting with the hose off the side on the side of my block, were those only on earlier 1fz's? Mine is a 97 since it wasn't previously stated. So many questions ugh:cry::censor:

Did you get the new one from Toyota, if so that is the correct part, and if you cannot start it, someone did a no no and damaged the threads, also put pipe dope on the threads always for pipe threads
 
It is a new plug from toyota, and I agree with rifleman that it's probably just a burr. But all the Internet cruising says 14x1.25 is 20.3 tpi. Not trying to argue, just no one has specifically confirmed it's bspp, just what we were all figuring since everything else seems to be that way.

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Here is a side by side of the new plug with the old plug, you can see the first few threads on the old one are almost completely flat.

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Ninjaracing wrote, quote "It is a new plug from toyota, and I agree with rifleman that it's probably just a burr. But all the Internet cruising says 14x1.25 is 20.3 tpi." end quote. Your correct, 14MM X 1.25 is in fact 20 threads per inch, I'm sorry to say i looked at the wrong place on my thread chart when i posted that, all well, once you get over 60 your eyes don't work so well. Since your old plug has so much damage to it's threads, your going to need to buy a tap to fix the threads in your block. One more thing, could you please take a photo of both the new, and old plug next to a tape measure, or a machinist pocket scale. With that information I might be able to help you settle on what thread size your working with.
 
You may have been mistaken on thread pitch, but I was mistaken on which bolt I had used, and it was in fact 14x1.5 which is 17 threads per inch, which makes you actually correct. Haha we will just call it even

Anyways, I took it by a machine shop I use through work to settle it once and for all... according to his measurements it is 14x1.5.
But until it is fixed and installed correctly I'm not swearing by anything so I will post progress, and the picture you want when I can
 
The threads in the block don't look obviously mangled. I'd be attempting to get a good image of what's going on in there. Mirrors, lights, whatever..
 
Ninjaracing13, I did some research, it looks like that plug seals the hole in your block from leaking fluids by using an inverted flair tip, just like brake bleeder screws do. Since inverted flairs uses the tip to seal, they don't rely on tapered threads for sealing like BSPT or NPT plugs do. So since you were able to screw that new plug on to a 14MM X 1.50 nut, it can't be a BSPT or NPT plug. Because of that fact i now think you can use a regular 14MM X 1.50 tap to clean out the threads in your block. If it were me, I'd try a 14MM X 1.50 bottoming* tap, I'd start it in the block by hand, if it screws in 1 full turn by hand then put a wrench on it, and turn it in SLOWLY, if it starts to turn real hard, STOP TURNING! But i think this is going to be the answer to your problems. Once you've cleaned that hole out, I'll bet that new plug screws in by hand. * You'll need to use a bottoming tap because of the inverted flair seat at the bottom of the hole on your block.
 
These should tap as Rifleman said, with a STRAIGHT thread, metric BOTTOMING pipe tap. (Also referred to as a "blind hole tap")

From a RYCO website:

  • BSP is BRITISH STANDARD PIPE – Also known as Whitworth 55° Thread Form
  • BSPT is BRITISH STANDARD PIPE TAPER – Thread form per AS 1722.1, BS 21, ISO 7
  • BSPP is BRITISH STANDARD PIPE PARALLEL – Thread form per AS 1722.2, ISO 228
BSPT male threads seal against threads of fixed BSPT female.
Contact is made on the flanks of the threads.

Use of a thread sealant is recommended for BSPT male to BSPT female connections.
Measure the BSPT male thread OD and female thread ID at the first full thread near the end of the fitting.

BSPT male and BSPP male with conical 30° seat (60° included angle) seal against matching conical 30° seat of BSPP female swivel.

BSPP O Ring male connector has straight threads and O Ring with metal Retaining Ring. It seals against flat external surface of BSPP female port.
BSPP male, with chamfer to locate Bonded Seal also seals against flat external surface of BSPP female port.

Surface irregularities require a Spot Face to ensure effective sealing. Elbows and tees have Lock Nut to allow orientation of fitting to required direction.

BSPP male and BSPP female flat face swivel require a suitable soft washer between faces to seal. For low working pressure.
---------------------------------------------------------------------------

Do NOT use pipe dope or thread tape on non-tapered pipe threads.
 
Ok boys and girls, I seem to have it fixed. Came to the conclusion that there was no way that brass plug was going to fit in my block so I did some mud searching, and ordered a couple of the other plugs that were used on other 80s. Turns out petcock style plug is the one my block is sized for, I know they were used on the earlier 1fz's. Maybe my block isn't original, or maybe it's just an oddball one because it was manufactured 11/97. Who knows. But it fits just fine.

The threads on the two other plugs measured .5110" one was a slightly finer pitch, and the petcock matched the 1.5 pitch of the brass plug.

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