[Seon]

I bought a set of Dolphin gauges and removed the existing OEM sender on the 5.3 Vortec engine to install the Dolphin temp sender but immediately realized that they are two different size threads.
I spent over an hour at NAPA and AutoZone parts shop looking for the correct adapter without any luck.
Has anyone installed an aftermarket sender on a '00 GMC Vortec engine and if so, where did you find the adapter?

The one on the left is the Dolphin sender, the one on the right is the GMC sender.

 

[Seon]

Thought I found the adapter at Car Quest Parts but theads would fit in the head

 

[4 Jaw Chuck]

You may want to keep the original sender in the block and find another NPT port somewhere in the manifold, finding an adapter might be impossible.

 

[Seon]

The engine is a 2000 GMC 5.3 Vortec and I sure can't find a NPT inlet anywhere??

I find it hard to believe that with all the "hot rodders" around, I seem to be the first one to use an aftermarket gauge on a Vortec engine.

Also, I would have thought that the Dolphin gauge manufacturer would have provided that adapter in the Quad kit I bought

 

[roys63]

I think what you have is the coolant temp sensor for the computer, is this a two wire sensor? You must have this if you are still running the fuel injection. This is not related to the temp Gage sender.

 

[arch]

Try home depot or lowes, or some other hardware store, I've found many rare adapters there... normally in the plumbing section, but you can find em elsewhere in the store as well.

Or on second thought, another way around it, a simple explantion, take the sender wire from the stock sensor and wire it up to the aftermarket gauge... but you'll need alot more info from the sender and gauge before you attempt something like that.

 

[BstMech]

You might get lucky and find that they have the same temperature/resistance values. In which case you could use the factory sender unit. That does look like the two prong unit used for the ECM though.

 

[Seon]

I think what you have is the coolant temp sensor for the computer, is this a two wire sensor? You must have this if you are still running the fuel injection. This is not related to the temp Gage sender.

The OEM sender in the pic above is indeed the Engine Coolant Temperature (ECT) sensor which I planned to re-install. What I understand is that this is a resistor which varies the value of it's resistance in accordance with the temperature changes, which directly affect the voltage signal from the sensor to the PCM.

I was planning to install the aftermarket sender in the engine head on the passenger side.

For Arch: I checked with NAPA, AutoZone, Car Quest, Home Depot, Lowes and Ace hardware with no luck.

For All: Other than the two inlets (one on each head), is there anyother port I can install the aftermarket sender? I'm an "old school" wrencher and this is the first computer engine I've dealt with and I'm at a lost .

 

[Lonestar]

What are the threads (original and aftermarket)?

I probably have one I can send you.

 

[4 Jaw Chuck]

Without the thread dimensions I can't find the exact adapter your looking for but I do know that the fitting you removed is a "G" thread or straight pipe. The actual thread is important since some manufacturers used metric versions of standard straight pipe just to be different, I don't think Chevy did this but thought I would warn you.

Here is a page that has many different "G" thread adapters that go to NPT but you best get your hands on a thread pitch gauge to measure exactly what you have there.

G to NPT adapters.

The fittings listed are for vacuum applications and are chromed brass instead of plain brass, they will work fine as long as you don't mind the shine. Reuse your copper washer to seal the fitting, vacuum applications use o-rings.

Hope this helps.

 

[NorthStar]

Here is another neat article that a friend showed me today.
It might help you identify the threads.

Name that thread

 

[Seon]

Using my very old measuring tools and using the links you provided as a reference, here's my conclusion.

The OEM sensor has a British tapered thread...G3/8 with 19 threads .

The aftermarket sender has 1/4"NPT.

Here's a pic of an adapter I bought this afternoon thinking it would fit in the engine head...but it doesn't. It's about .060" larger than the metric thread on the sensor.

Please note that the lower pic shows the adapter that has the 1/4"NPT inside threads. The upper pic has the adapter threaded on the sender. And if it was the correct adapter, the outside thread should be the metric tapered