Intake Manifold Cover?

[StickyLifter]

Hi Everybody,

Kind of a long story. I haven't owned my truck very long. It's a 84 Sierra, but has a Chevrolet engine in it. I tried to change my coolant temp sensor yesterday and the one I had picked up was too small. I think the parts store has the correct one on the way, but that got wondering exactly what engine I have. I was trying to get a view of the numbers on the block and noticed this cover/patch on the intake manifold. Has anybody seen something like this or know what he hole could have been for?

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Thank you,
John

 

[scrap--metal]

That is an EGR block off plate. Your truck has had the exhaust gas recirculation (EGR) system removed. No big deal as long as it's sealed and not leaking.

Sorry I don't have anything to add regarding the different temp sending units.

 

[StickyLifter]

That is an EGR block off plate. Your truck has had the exhaust gas recirculation (EGR) system removed. No big deal as long as it's sealed and not leaking.

Sorry I don't have anything to add regarding the different temp sending units.

Thank you for the info!

 

[Bextreme04]

its not uncommon for the CTS to be a smaller size, you just need to get a brass fitting to size down from the bigger hole in the head to the smaller sensor.

 

[75gmck25]

Some of the older engines used a 3/8” thread sensor, but most later engines had a 1/2” thread sensor. The sensor size can be adapted, but the most common problem is that the sensor resistance is not a match to the gauge. GM changed the gauge setup over the years, so a sensor for your ‘84 truck might fit my ‘75 but the resistance values would be wrong, and the gauge would read wrong.

 

[StickyLifter]

Some of the older engines used a 3/8” thread sensor, but most later engines had a 1/2” thread sensor. The sensor size can be adapted, but the most common problem is that the sensor resistance is not a match to the gauge. GM changed the gauge setup over the years, so a sensor for your ‘84 truck might fit my ‘75 but the resistance values would be wrong, and the gauge would read wrong.

Thank you for the info. I think I have the correct sensor now.

 

[84Squarebodlvr]

Some of the older engines used a 3/8” thread sensor, but most later engines had a 1/2” thread sensor. The sensor size can be adapted, but the most common problem is that the sensor resistance is not a match to the gauge. GM changed the gauge setup over the years, so a sensor for your ‘84 truck might fit my ‘75 but the resistance values would be wrong, and the gauge would read wrong.

What thread sensor is

 

[84Squarebodlvr]

Sorry! First time on here. What size sensor is this blue gauge in the manifold to the left of the thermostat housing? Thanks! I have a 1984 K20

 

[Turbo4whl]

The blue colored sensor is a TVS, (Thermal Vacuum Switch). It is used to switch vacuum on or off as the engine warms up. On your truck it looks like there isn't any vacuum hoses hooked to it. Someone has disconnected it's use. Now it is just plugging the pipe port in the intake manifold coolant passage.

The pipe size is either 3/8" or 1/2". There should be a vacuum hose decal on the radiator support or air cleaner that shows all the vacuum hoses your truck was built with.

The temperature gauge sensor is usually mounted in the drivers side head. It has one wire connected to it.

 

[Turbo4whl]

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[Rusty Nail]

See?!
I'll thought I was messin around talking about pinché thermostatic vacuum switches! WELL, THERE IS ONE!
:hornz:

It gots a pintle!