How Timely Mr. Leigh!

Leigh sent me a message with a picture of an automotive thermostat that had a small hole drilled in it out towards the edge a day or two ago and was wondering if I had ever heard of this trick.

I replied that yes I had and had been doing that for years.

It’s a good tip to pass on, that’s what us mechanic types do.

Anything to make life easier for the next guy, especially if we have run into some crazy nightmare bullshit and have figured out an easy way to fix it.

It just so happened that I decided to go out and change the thermostat on my Caballero this morning as a bit of precaution since I started having problems with it.

The old thermostat is on the left and the one I put in is on the right.


The little hole helps air to escape which is especially helpful these days on engines that are prone to getting air pockets trapped in the cooling system and it also seems to help them operate more smoothly so you don’t get the thermostat slamming open and shut as the engine warms up.

Hopefully this will be the end of any cooling system issues.

The gauge doesn’t work right in the first place because the flexible printed circuit board behind the instrument cluster has got bad contacts on it somewhere and these older GM rigs were notorious for that. You can still find them for some rigs but not for this fucker apparently because I have looked.

The GMC version of the El Camino had a different gauge package than the Chevy version.

Of Course.

I have a little after market 3 gauge set that I think I am going to install to get past this issue.

The only problem there is that it isn’t going to help the gas gauge not working issue.

I have been using the trip odometer for that since the day I bought it and found out the gauges are fucked up.

I put gas in it every 100 miles whether it needs it or not.

Amazingly enough, at 37 years of age, the old bastard still gets 20 miles to the gallon.

This is a good thing because it only has a 10 gallon tank.


I can’t believe they didn’t put a bigger tank underneath the ass of these things.

8 thoughts on “How Timely Mr. Leigh!

  1. Phil- I had an 88 Chev 2500 350 that would squawk low oil press after 30 mile. It was cracked diaphram in sending unit that let oil leak to other side during operation. Considerable cleverness on my part expended to diagnose. Not much of that left.


  2. Had a ’97 S-10 for twelve years with a bad gas tank sending unit. It wasn’t worth replacing it since you had to pull the gas tank. So I just did the odometer thing. It was easier on my ’54 Ford since you just went through a port in the trunk floor. Strange thing about the S-10 unit, speaking of GM. The four-cylinder, five-speed, short bed was the only model, according to the shop manual, where the sending unit could be replaced without replacing the whole fuel pump assembly for a lot more money.


    • The fuel pump/sender module on my daughter’s 2005 Escape is accessed through a panel under the rear seat. Getting it out of the tank afterwards really sucked. You have to lay on your stomach and reach into the tank to unclip it from the bottom part from the tank. When it has half a tank of fuel, and you are face down in it for an hour, the fumes are terrible. That and when you pull out the module, it drools gas all over the carpets.
      Then to top it off, it wasn’t the fuel pump, but the fuel pump driver module.

      Whitehall, NY


  3. During the at 37 years have you replaced your head gaskets? There are a couple of drill points to open up new water flow channels that help keep a small block the same temp all over the block. That, porting the intake and exhaust with a little extra material removed on the exhaust, a set of long headers does wonders. I helped a buddy do this to his 1981 Malibu 350. It had a leaky head gasket that he wasn’t aware of. He gained about 3mpg to get about 21mpg and a lot more throttle response,


  4. Yup, I’ve been doing the drilled T-Stat trick for 35+ years. My preference is to run a 180F ‘stat on a carbed engine, daily driver. 160 F on performance carbed engine, hot rods. A modern fuel injected motor needs at least a 190 T-stat to get the ECU to go into closed loop. Otherwise they run pig rich all the time, possibly wrecking the cats.

    On the other hand, all of my race motors used a T-stat sized washer to restrict the flow in the system. Most of the time it was simply a gutted T-stat. Under race conditions, on the hottest days in Vermont, it never got above 205 F. Typically 180 -190 F most of the time.
    Personally, I don’t think it had to do with the flow rate of the system. I postulate that the restriction at the T-stat caused a rise in pressure inside the engine – which raises the boiling point just enough to prevent localized air pockets inside the water jackets. An aluminum Griffin radiator, Howard-Stewart high flow water pump, fixed pitch six blade steel fan and a tight fitting shroud helped a lot too.

    Thanks for the nod, Phil.

    Whitehall, NY


    • Leigh,

      I could not have said it better. Every thermostat I installed (for only 25 years) had a hole in it. Some actually actually came with a hole and a little jiggle pin in it.

      Did race a Formula Ford though and it did have a gutted out tstat in the thermostat housing. Never had an overheating problem with it.


  5. FYI: if you have any thoughts on purchasing or using one of those cooling system vacuum fill systems, be extremely careful. Many of the people who manufacture these tell you it is okay to pump these up to 30psi for vacuum before flipping the valve to start drawing the coolant back into the system. The problem is most water pumps have a one-way seal for a system that runs about 12-18psi of PRESSURE, not vacuum. I was on a job and the boss told me to use this contraption. While filling at the recommended 30psi, we heard a loud snap and passed it off as one of us stepped on a piece of tie strap. After running for five minutes, the engine puked out 9 gallons of coolant. Seeing as I just changed the EGR cooler, I figured the water pump had POSSIBLY been weak – change pump and repeat with a maximum 16psi on the gauge. When we seen what had transpired with the brand new pump starting to leak (and a severe tourettes episode), the fancy tool was shelved and everyone in the shop returned to the old school method.
    I would shove that thing up my tool dealer’s ass, however that would be physically impossible, as that oriface is currently occupied with a computer scan tool.


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