teflon tape OK on injectors?

[motomike33y]

put 85 golf motor in my 91 jetta.  put my prior good injectors in and they are slowly bubbling around the base.  starts and runs ok, but obvious air leak.  now I see why PO had something like caulking on the old injectors which I'd removed.  have new shields but need something to tighten up the threads a little.  teflon tape ok or is there something better?  mike

[Luckypabst]

Teflon is for tapered thread fittings, so no. I'd run it and hope for it to collect enough carbon to seal itself... or maybe even pull it all back down and attempt to correct the problem. 

[vanbcguy]

Definitely no...

The injector threads aren't meant to "seal" anything at all.  The only thing that does any sealing is the heat shield.  If you think they're leaking, then the heat shield is where you need to focus your attention.

It's not too abnormal to have a little bubbling around the threads after changing injectors btw, but it's usually caused by whatever diesel leaked down in there around them when the lines came off.  It's due to heat usually rather than leaking combustion gasses.  If there's diesel or motor oil in there, they'll bubble once they're hot till it burns off.  After a week or so it'll stop.

The only thing I'd ever put on injector threads is anti-sieze, and that I'd use prolifically.

[motomike33y]

thanks-the injectors are tight w/new shields so I'll wait and see.  thanks for the input

[rabbitman]

COuld check the surface of the head where the heat shield seals and see if it's got an imperfection.

[Toby]

Or more likely carbon from some time when they were loose or someone reused the heat shields. They are only a buck a piece on the net so every diesel owner should have a few new ones floating around.

If you want to know for sure whether it is a leaking heat shield or diesel boiling off look at them when the engine first starts. If it is bubbling its a leak.

[motomike33y]

it starts bubbling as soon as some fuel drips down.  I'd cleaned out under the shields--which are now $3/apiece-not $1-but that may be the issue.  I've tightened the injectors down

[Toby]

.98 cents each with free shipping over $50.

http://www.autohausaz.com/search/product.aspx?sid=crusin55jqjuzy45tp4ijw45&makeid=800026@VW&modelid=1285455@RABBIT%20L&year=1984&cid=22@Fuel%20%26%20Air%20System&gid=6060@Diesel%20Injector%20Heat%20Shield

Be very careful to torque the injectors to the proper value (51 fl/lbs) and no more. All of those heads that are cracked through the injector boss are from somebody trying to seal a compression leaking injector.

Are they all leaking or just one? And you have made sure that the heat shield seat in the head is bright and shiny? I often use a new plumbers brush for cleaning the inside of 3/4" copper fittings for this. And you are using new neat shields EVERY time?

[motomike33y]

thanks for the link.  yes they are new.  I've probably over-torqued them as I did it w/out the torque wrench-but not to the point that anything was breaking loose.  I think at least 3 are leaking now. Starts and runs ok, but little bubbles form around the injector base.   None were leaking before I removed the old ones--which were tight, difficult to turn, because of some type of caulk-like compound on the threads.  I always use anti-sieze.

[motomike33y]

I've rarely had injectors leak on other motors in the past, when they did it stopped when I torqued it down snug.  I'll order more shields, and let this one run and see if it gets better.  If not, I may try the teflon to see what happens-don't think it will make anything worse?

[Luckypabst]

My concern would be the increased pressure on the threaded boss from having the teflon in there.

Chris

[BigVWman]

In addition to the pressure of the tape it alters the friction big time possibly allowing you to overtighten them easily!