1987 Chevrolet 350 tbi high idle

[idahovette]

Next time you have your thermostat out drill a 1/8 hole in it around the edge, prevents "air pockets" in the system.......the "grub screw" as you call it is still above the thermostat so that won't bleed the air??

 

[iamtherealJayy]

@Rusty Nail honestly don’t know how to but I can figure it out, if I’m replacing the water pump should I replace the timing chain cover gasket as well? Or don’t bother? I don’t want to take too much apart

 

[iamtherealJayy]

@Rusty Nail got any brand recommendations for the water pump? Oreillys has Murray and Masterpro. Or should I just order one off partsgeek

 

[Bextreme04]

@Rusty Nail got any brand recommendations for the water pump? Oreillys has Murray and Masterpro. Or should I just order one off partsgeek

I agree with rusty... replace the water pump. The water pump is what prevents you from accessing the timing cover to change the gasket, but the oil pan would also need to come off, so that might be more work than you are looking for. The water pump is an easy change, timing gasket adds more work. I used a NAPA pump on my 454. I have an oreilly murray one on my 350.

I would recommend since the engine has been running with a huge vacuum leak for so long, that you should unhook the battery to reset the ECM now that you have fixed the vacuum leak. The IAC and LTFT/STFT(fuel injector trims) are going to be all out of whack from it trying to compensate for the vacuum leak.

When the truck is overheating, what does the upper and lower radiator hose feel like? Are both of them very hot? The top is the exit from the engine and the bottom is a suction line into the water pump. If the top is very hot and the bottom is cold, you either have a bad pump, bad thermostat, or a clogged radiator. What about the heater hoses? Are both hoses hot? One hot, one cold?

 

[iamtherealJayy]

@Bextreme04 the battery was unhooked while I swapped the gasket. I’m working on getting a water pump, I don’t know how the lower hose feels or heater hoses I didn’t think to grab them. But the upper radiator hose gets really tight until the thermostat opens

 

[Bextreme04]

Also, 650rpm is the correct manual idle set rpm with the IAC fully closed. The IAC should then be able to open and close to hold the RPM at around 700-750RPM. Once you get a new timing light and get the timing correctly set(which will require the engine to be able to get fully warmed without overheating), you should then go through the IAC set procedure.

 

[iamtherealJayy]

I’m working on getting a timing light and infrared thermometer. I need to advance the timing very slightly. Do I have to remove the power steering and alternator to change water pump?

 

[Bextreme04]

@Bextreme04 the battery was unhooked while I swapped the gasket. I’m working on getting a water pump, I don’t know how the lower hose feels or heater hoses I didn’t think to grab them. But the upper radiator hose gets really tight until the thermostat opens

The upper radiator hose shouldn't get tight UNTIL the thermostat opens... the coolant is pumped out of the bottom of the radiator and flows only through engine and out the heater hose back into the radiator until the thermostat opens and lets the coolant flow through the upper hose. I wonder if you have a reverse rotation pump from a later TBI with a serpentine pulley system?

 

[Bextreme04]

I’m working on getting a timing light and infrared thermometer. I need to advance the timing very slightly. Do I have to remove the power steering and alternator to change water pump?

You do on mine, but its like a 5 minute job with a 9/16".

 

[iamtherealJayy]

The water pump should be the original one, the truck has low miles the only not original part is the block.

 

[Bextreme04]

The water pump should be the original one, the truck has low miles the only not original part is the block.

I can't imagine a situation where I would put an old water pump on a new block... What block is it now? If its from a newer TBI truck and they just swapped the accessory drive system over, that might be your problem. The V-belt system drives the water pump in the same direction as the crank. The serpentine belt system drives the water pump in the opposite direction from the crank. So if you have a reverse rotation pump from a serpentine belt system being driven by a V-belt system, the impeller is turning the wrong direction.

 

[iamtherealJayy]

The block was a carbureted engine from a dirt track race car. $500 complete engine(15-20 years ago) and dad just took the block and swapped them since he’s blown the engine. I mean he might’ve replaced the waterpump when he had it all apart but I highly doubt it. The truck has just over 94000 miles on it now, the block in it has around 30k since it was put in. If you know which direction it should spin I can go check the belts and tell you something useful maybe? I can send pictures and the routing of belts. It’s the 3 belt system, one for air pump one for power steering and one for water pump I assume? Although I believe the water pump has two belts on its pulley. But not 100% sure been a while since I’ve changed the belts.

 

[Bextreme04]

The block was a carbureted engine from a dirt track race car. $500 complete engine(15-20 years ago) and dad just took the block and swapped them since he’s blown the engine. I mean he might’ve replaced the waterpump when he had it all apart but I highly doubt it. The truck has just over 94000 miles on it now, the block in it has around 30k since it was put in. If you know which direction it should spin I can go check the belts and tell you something useful maybe? I can send pictures and the routing of belts. It’s the 3 belt system, one for air pump one for power steering and one for water pump I assume? Although I believe the water pump has two belts on its pulley. But not 100% sure been a while since I’ve changed the belts.

It doesn't necessarily matter which direction it is spinning now, but what direction the pump is meant to spin. The impellers are different in order to pump the fluid in the proper direction when the pump is turned in the direction it is intended to turn. It doesn't sound like you should have ended up with a reverse rotation pump, but it does sound like the pump you have is exceptionally old. I'd check what all the hoses feel like when it gets super hot and then change the pump regardless. If you are feeling up to it, it's probably not a bad idea to get a timing cover gasket set and an oil pan gasket set too. Degrease and clean the heck out of everything, then pull it all apart and clean it more. Then replace all the gaskets and throw it all back together. You'll probably want to rent a three arm puller and a harmonic balancer install tool when you go to buy the parts, since you'll need to pull the balancer to get the timing cover off and then reinstall it. Don't try to use the balancer bolt to draw it back on or you will strip the threads in the crank.

 

[iamtherealJayy]

I’ll probably leave the timing cover gasket alone for now, just clean everything since it’s a very slow leak. But I can get a new water pump for $45 or so at oreillys. I’ll replace it just to get it out of the equation.

 

[Bextreme04]

I’ll probably leave the timing cover gasket alone for now, just clean everything since it’s a very slow leak. But I can get a new water pump for $45 or so at oreillys. I’ll replace it just to get it out of the equation.

Did you say earlier in this thread that you have a new thermostat, radiator, and cap? Do you have a picture of the heater line routing? Does your heater function(i.e. does it blow hot air when the temp is reading high)?