vacuum ?

[CJ_4]

I have a 97 K1500 with the S engine. I think I need to replace the vacuum pump, but I thought about getting a turbo master and a pcm from heath. If I do this, would I still need the vacuum pump for the egr or anything else? Also, if I would still need it for the egr, how hard would it be to do away with that? thanks for the help.

[chevy1988]

I'snt the breakes vaccum assisted to..? if so you will need it for that I would think. And I might be wrong on this but I also think the AC and Ventilation valves inside/under the dash uses vaccum to operate...

Might be talking my head of here but I thought I would mention this anyhow :)

[DmaxMaverick]

The brakes are hydraulic assisted, powered by the power steering pump. The hydroboost unit (located behind the brake master cylinder, where the vacuum booster would be, if it had one), is unique to the Diesels and GM heavy LT and MD trucks (even the gassers).

Vacuum on the later trucks is only used for boost control and EGR. On the earlier trucks, it is needed for HVAC control and EGR. This is if the vehicle is equipped with EGR. The EGR is an emissions system, and tampering with it is not legal. However, it can be disabled/removed for testing and diagnosis purposes. How long you choose to test/diagnose the system is up to you. If you have a later model truck (1994+), the vacuum pump is not needed if the EGR and boost control isn't in use. 1992-3 6.5L trucks only have a vacuum pump for EGR. Previous 6.2L trucks are the same, except the HVAC is vacuum operated on earlier models (before the push button HVAC).

[CJ_4]

I appreciate the input fellas. To disable the egr, is it anything more than just putting a freeze plug in it and disconnecting the wires? Can it be done with the stock computer?

[DmaxMaverick]

For a most thorough test, an F code engine intake would be best. But plugging the EGR port would work. With the stock PCM, you should leave the wiring and solenoid valve intact. If you remove it, you will get EGR DTC's. A custom program PCM, or an F code PCM could stop the control and monitoring of EGR function.

[qaz1]

Interesting, I presume this is the 31,33,44,45 codes one might get if per chance they were to test a 95 6.5 S-code with an F-code intake assy and the two egr "air" solenoids unplugged? It appears the F & S code PCM are the same - is it just the Eprom plug in that is different?

[DmaxMaverick]

Interesting, I presume this is the 31,33,44,45 codes one might get if per chance they were to test a 95 6.5 S-code with an F-code intake assy and the two egr "air" solenoids unplugged? It appears the F & S code PCM are the same - is it just the Eprom plug in that is different?

Correct...

[CJ_4]

so by only plugging the egr and leaving the wires plugged in i wouldn't get a code correct? what size plug do i need?

[DmaxMaverick]

It depends on what you're plugging. If you plug a soft vacuum line ("temporary" test), golf tees work. Electrical tape works for the small hard lines, wrap it (half the tape on the line, half off) and pinch the end (also temporary). You can also use old style carburetor vacuum tube caps, some parts stores still have these. If you remove the actuator and plug the big hole (less temporary), a frost plug will work, but I don't remember the size. It must fit tight. You could also fab a plate the shape of the actuator base. I have not done this on a 6.5TD, so you'll have to search the forum for more details. For a more extended test period, I suggest installing an F code intake.

You should get no DTC's if the solenoid valves are left in place. The PCM doesn't monitor EGR function and results. Only its solenoid continuity.

[JohnC]

With the "S" programming you need a functional vacuum system including both EGR solenoids and the Baro sensor to avoid setting codes.

That said, if an EGR code sets all it does is turn on the SES light. Some states' ispections will fail if codes are set.

I heard of one instance where a frost plug in the EGR chimney somehow found its way into the turbine side of the turbocharger. Hard to believe, but expensive to go through. Better to fashion a plate to bolt on where the EGR valve is now, or the "F" intake...

[qaz1]

F-intake is much more open to allow considerably greater air flow, should also run cooler w/out hot exhaust gas flow, and with the gasket to provide spacing the old egr valve bolts in place right on top of F-intake so all hoses, solenoids may remain hooked up during the test. F intake (upper & lower) can be had off ebay very reasonably.