420A oil leak?

[studabaker]

My freshly rebuilt 420a engine (after spun bearing) - I am getting oil leaking out of the oil sensor. I am thinking plugging it, temporarily, and running it to get it hot and this would melt any assembly lube and stuff... This also seems like a potentially bad idea. I was also considering installing an after market oil sensor. I do not rebuild engines enough to know if this is a normal thing to melt assembly lube if I used too much or something. It appears to be coming out of the middle of the sensor itself rather than from the threads.

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[dwb]

Have you tried a thread sealant? Teflon tape probably isn't the best option if that's what I see in your picture.

 

[BLACK'98DSM]

You don't need any sealant. The sensor and block are NPT (pipe thread) and should naturally seal when torqued properly. I'm going to say that you cross threaded it. There is too much visible thread. The hex head should land closer to the block but not quite flush. Remove the sensor and see if the threads are damaged. If so, check the threads in the block. If the block is good, just get a new sensor and try again. You should get 2-3 smooth turns by hand before there is enough friction to require a wrench.

You also REALLY need to clean those water/coolant passages. It won't flow worth a damn and would likely overheat the cylinder head as is.

 

[studabaker]

Thank you so much for your replies. This is the second sensor and it is backed out slightly because I was messing with it. I did use Teflon tape, yes, and it is not leaking from the threads. This is super weird to me and the reason I took the head back off. I was convinced I messed up the head gasket. I ran it for maybe 30 seconds with Teflon tape to verify it was leaking from the sensor itself. I had oil in the head but I still wanted to verify my work was good.

I want to install a plug I got from home depot. Apparently a 3/8" brass pipe fits perfectly. My threads are good.

Then I think that is a bad idea and I should install an after market oil pressure sensor. I am tempted to just run it for a few minutes and it will work itself out but that does not seem good.

Thank you for helping. I have thread locker but its coming out of the sensor, based on visual inspection.

 

[dwb]

NPT threads generally need a thread sealant. NPTF or BSPT do not need a sealant.
https://www.industrialspec.com/abou... and NPTF thread,seal without using a sealant.
04608303AB or M04707670 as best I can tell is the PN of your sensor. Those come from the factory with a thread sealant on them.

I have thread locker

Not a thread locker (Loctite), but thread sealant. However, it sounds like you have an internal failure of the sensor so you should consider a replacement.

 

[97egl]

My freshly rebuilt 420a engine (after spun bearing) - I am getting oil leaking out of the oil sensor. I am thinking plugging it, temporarily, and running it to get it hot and this would melt any assembly lube and stuff... This also seems like a potentially bad idea. I was also considering installing an after market oil sensor. I do not rebuild engines enough to know if this is a normal thing to melt assembly lube if I used too much or something. It appears to be coming out of the middle of the sensor itself rather than from the threads.

Melting assembly lube is not normal or even a thing anyone does. The assembly lube will get mixed in with the oil and when you drain the oil after the break in period the lube will drain out with it.

I cannot tell if you think the assembly lube and sensor leak are related but if that's what you are thinking they are not. If the sensor is leaking thru the middle/electrical connector, it is shot and needs to be replaced. Then continue with your engine break in.

 

[studabaker]

I will apply high temp thread sealant to a new sensor. I was not aware of this. The leak did not flow down the block, as I would expect from a thread leak. I continued to get a leak with Teflon which appears to not be the correct fix. I absolutely thought the assembly lube caused a back pressure situation. Or some other assembly mistake on my part, caused this leak. I will certainly clean up those coolant pathways.

The knock sensor should have this sealant as well I would presume. While I'm back there I think I will apply some high temp Permatex sealant to the other sensor which I believe is the knock sensor.

Thank you.

 

[dwb]

You don't want anything on the knock sensor or it may affect its sensitivity. It should be mounted in a blind hole anyway.

 

[studabaker]

Thank you that as well.