Oil temperature bulb adapter

[M Towsley]

I was planning on changing out my oil temperature gauge today when I was changing the oil. Turns out the original bulb on the old gauge is about 3/8" diameter and the bulb on my newly rebuilt gauge is about 7/16". The new bigger bulb will not fit in the adapter that screws into the back of the oil screen housing. The gauge restorer wants to ream out and taper the old adapter, however, that will really thin the metal out on the adapter. Is there an adapter made for the larger bulb, or did they just put the wrong bulb on?

[M Towsley]

Re: Oil temperature bulb adapter

Pictures of the new, old and adapter.

[Robert Lees]

Re: Oil temperature bulb adapter

My first thought are that your old bulb (with the square end) is incorrect, and that the rounded-end bulb is the correct one.

I've had these Bourdon gauges re-made by vintage automotive folks with no problem.

Rob

[M Towsley]

Re: Oil temperature bulb adapter

The old, small square bulb is the only one I have ever seen. The newly rebuilt one is the larger rounded-end bulb. The oil temperature gauge adapter, which is the same on the last four A-65's I have had as well as the three at the A&P school here in town are all for the small temperature bulb.

The gauge restorer, John Wolfe & Co., put on the larger bulb when they restored the gauge. Scott/AVOX started putting on the larger bulbs, see here and choose the pdf at the bottom: http://www.cessna120-140.org/forum/viewtopic.php?t=1988

It appears as though the bulb adapter carried by A/C Spruce may be the correct one, part number 95527. I confirmed it is made for the 7/16" large bulb and looks to have a beveled edge for the new temperature bulb.

[astjp2]

Re: Oil temperature bulb adapter

Just get a new adapter, that is the least amount of headache. Tim

[M Towsley]

Re: Oil temperature bulb adapter

Hey Tim, that is the plan, lol! Ordered the one from Spruce yesterday, that is, if it is the right one. Not a lot of sources out there for that particular part, and again, if it is the right one. No one lists the specs for it in their catalogs or on-line ads. Then when you call them up to get the specs you get a lot of quiet on the other end of the phone.

[astjp2]

Re: Oil temperature bulb adapter

I would have went to autozone or CARQUEST, but that is me......they use them in antique cars and are pretty common since all of the new bulbs are the larger ones. Tim

[M Towsley]

Re: Oil temperature bulb adapter

I actually had a nice selection at home but they were pretty much all metric. Thanks for the heads up though.

[M Towsley]

Re: Oil temperature bulb adapter

Tim,

No luck at any of the local auto supply stores. Several of them just looked at me funny. You must have smarter folks out your way, lol. Just hoping the Spruce adapter will work, I will let you know.

[M Towsley]

Re: Oil temperature bulb adapter

The A/C Spruce fitting is not tapered it is flat. And the search goes on.

[Guest]

Re: Oil temperature bulb adapter

I confess confusion on this Marty but I do have some of those adapters.

Tell what you are looking for and I will see if I have such an item.

Dave

[M Towsley]

Re: Oil temperature bulb adapter

The new bulb is about 7/16", not the smaller 3/8". The new bulb has a tapered end that must fit into the tapered female part of the adapter to create a seal. If you have a few minutes, click on the link I posted in post #4 above. Down at the bottom of that webpage you will see a pdf. I had no clue about this issue until I ran into this. I know these adapters are out there but some folks probably don't want to let loose in case they may need them at a later date. Thanks Dave.

[astjp2]

Re: Oil temperature bulb adapter

I don't think your oil screen adapter should be pipe thread, it should have straight threads and an AN900 copper crush washer to seal it. Tim

[M Towsley]

Re: Oil temperature bulb adapter

You may be looking at the wrong item,Tim. The oil temp adapter itself screws into the filter with an900-10 copper crush washer. The threaded piece, silver threaded part behind the bulb in post #2 above, screws in with no gasket, the forcing of the bulb to the adapter is the seal. There is no other way to seal this piece, again, look at the pdf on the link above. Of course, the filter itself seals into the engine with an an900-28 copper crush washer.

[Guest]

Re: Oil temperature bulb adapter

Marty,

I found three.

Two are 3/8" i.d. with flat or tapered edge, one is 7/16" i.d. with tapered edge.

After looking at them (pictures attached) I think you could just have the 3/8" tapered bored or drilled out to 7/16".

Interestingly about 25 years ago I changed my oil temp and the new bulb was 3/8" but the old one was 7/16" so I very cleverly soldered a copper sleeve into the adapter. I guess if I had been paying better attention I would have used one of these adapters as I think I had them then!

Let me know if you want one of these, if so email me your address. I have it somewhere but it is from at least 10 years ago I bet.

Dave