Project Deimos: An LS '65 Coupe Build: Engine no longer overheating!

[JimStone]

Thanks for the kind words guys. I appreciate the encouragement





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To close the chapter on two recent head-scratching issues:


1) I figured out why my two Wilwood brake master cylinders have leaked at the outlet

I used Wilwood 1/8" NPT to 3AN adaptors to hook up the MC to my brake lines (used 37 degree/AN flares on my stainless brake lines). Paid a premium for the Wilwood name brand to ensure there would be no issue

https://www.summitracing.com/parts/wil-220-6956

You can see below that the NPT threads on the Wilwood adapter (bottom) are hardly tapered at all, compared to my generic replacement (top)



Without the taper, the interference seal never was solid. My cheap replacements adapters didn't need to thread in as far before there was resistance.

This is really annoying, because I initially assumed that I was the problem and over-torqued and broke the first master cylinder that leaked. I bought a whole new replacement MC.

Turns out it was just junk fittings from Wilwood


I have 3rd Wilwood master cylinder. That one uses a 1/8"NPT to 4AN fitting. It also was from Wilwood, but looks perfectly fine (adequately tapered). Fingers crossed.










2) Figured out why my two coolant sensors were reading dramatically different coolant temps. (...long explanation below - short version is it was the wrong sensor...)

My engine came with one coolant sensor already installed from Blueprint on the driver's side cylinder head. The second sensor came with the Holley Terminator X, which I installed in the passenger side cylinder head.

The Holley sensor clearly went to the Holley. The Blueprint one was already installed and had the correct connection to the Speedhut gauge cable, so I just hooked it up.

I actually had a 3rd coolant temp sensor that came with the Speedhut gauge, but it didn't seem like I would need that.



When running the engine, the Holley sensor was saying the coolant was heating up (actually overheating) but the Speedhut gauge's needle would hardly move. The thermostat clearly wasn't opening correctly (as per my previous posts), but was the coolant also not circulating through the engine?

I used an infrared thermometer to check for hot spots and the engine seemed to be heating symmetrically.

I tested and compared the resistance output coming from the two sensors and the readings were similar.

Only after I took the Blueprint sensor out and showed ChatGPT a picture did I learn the issue.


Below is a picture of the Blueprint CTS (right) and Speedhut sensor (left). Chat GPT informed me that I was trying to use an ECU sensor when a gauge sensor was needed. ECU sensors have a lower resistance range, thus why my Speedhut gauge was only very slowly rising compared to what I was seeing on my laptop in the Holley software.




So, there are two different coolant sensor types. You all probably knew that. Now I do too.

The Speedhut sensor did require a 1/4" NPT to 1/8" bushing, but got it installed and now both measurements are similar.

This was confusing, but I am very relieved. Means my engine isn't F-ed!