1990 GMC Sierra - Page 9 - Answered Questions & Fixed issues

This can be a simple loose connection or your fuel sending unit is bad which is located in the tank. the coolant temperature sender is usually located on the cylinder head or by the thermostat.

The sending unit inside the gas tank is bad

90 SAE

1. Verify power using noid style test light (normal test light will not work)
2. If noid light illuminates when cranking engine the problem is the injector itself.
3. If light fails to flash the problem is electrical (IE PCM).

canister lines likely vent for gas tank

likely you have a stuck heater contrll valve

check chapters for chilton manule

All pre 1995 GMC vehicles had to have an alarm system to have keyless entry... So, lift the hood and look for a red LED near the right front of the vehicle. If none - you don't have keyless... if yes, the you do.... and an alarm system too.

On the V8 engines it should be at the back of the block under the distributor I have also seen them down next to the oil filter on rare ocassions.

You'll have to remove the transmission in order to get to it. The flexplate (which is the equivalent of a manual transmission's flywheel) will have to come off of the engine as well, at which time you'll be able to work on getting the seal out. It's a very big job unfortunately.

i woud have them checked sounds like you need rear brakes the squeel you are hearing could be metal on metal which is what you hear when lining on pads or shoes gets low

well 1st ensure the hoses to the heater core are operating by touching them 1st the top hose and then the bottom hose they should both be hot to the touch if only the top hose is hot and the bottom hose is cold most likely your heater core is plugged up as this occurs from not using it and sediment sets in and connect a garden hose to the top and the bottom hose at the base and the top hose "Do not "use full force" when doing this as you risk rupture to the core ...when flushing it
this will help dislodge sediment and you should see gunk come from it ...
if both are hot to the touch then it may be the cable inside under the dash has slipped or a vacuum hose is pinched or come unconnected ...visual inspection on both issues is the only way to ensure they are working properly .
consider as well antifreeze levels and possible stuck thermostat ..{ just a note }
as well make sure the vacuum lines are especially the one under the hood are all connected as this is Vacuum that works the system ,...check for dry-rot and possible disconnected ..replace as needed
inspection of the vacuum hoses to the cluster under the dash should be fairly easy on your vehicle and use a flashlight drop light and even a hand held mirror in determining the exact cause to begin make sure the vehicles is running while working the levers and the switch this is where i would start 1st

The engine is kept cool by a liquid circulating through the engine to a radiator. In the radiator, the liquid is cooled by air passing through the radiator tubes. The coolant is circulated by a rotating water pump driven by the engine crankshaft. The complete engine cooling system consists of a radiator, recovery system, cooling fan, thermostat, water pump and serpentine belt.

Check the coolant level in the recovery bottle or surge tank, usually mounted on the inner fender. With the engine cold, the coolant level should be at the FULL COLD or between the FULL HOT and ADD level. With the engine at normal operating temperature, the coolant level should be at the FULL HOT or HOT mark. Only add coolant to the recovery bottle or surge tank as necessary to bring the system up to a proper level. On any vehicle that is not equipped with a coolant recovery bottle or surge tank, the level must be checked by removing the radiator cap. This should only be done when the cooling system has had time to sufficiently cool after the engine has been run. The coolant level should be within 2 in. (51mm) of the base of the radiator filler neck. If necessary, coolant can then be added directly to the radiator.

While you are checking the coolant level, check the radiator cap for a worn or cracked gasket. If the cap doesn't seal properly, fluid will be lost and the engine will overheat.

Worn caps should be replaced with a new one.

Periodically clean any debris; leaves, paper, insects, etc. from the radiator fins. Pick the large pieces off by hand. The smaller pieces can be washed away with water pressure from a hose.

Carefully straighten any bent radiator fins with a pair of needle nose pliers. Be careful, the fins are very soft. Don't wiggle the fins back and forth too much. Straighten them once and try not move them again. It is recommended that the radiator be cleaned and flushed of sludge and any rust build-up once a year. If this has not been administered within the stated time, this may be why your vehicle is overheating at this time. Have the Radiator flushed asap if this is the case.

Now, if the coolant level is proper and, the cap is in fair or good condition, i would advise to move in the direction of the cooling fans and sensors as well. These fans are vital to the cooling process as well. The cooling fans must cycle in intervals to keep the coolant cool during stop and go driving or, long idle. They are also very important during the operational period of the AC during travel as well. i recommend inspecting the cooling fans while the engine is running. they should cycle during the running period. if this is not the case, you will need to test the operational value of these devices. The test procedure follows below


TESTING


1. If the fan doesn't operate, disconnect the fan and apply voltage across the fan terminals. If the fan still doesn't run, it needs a new motor.

2. If the fan runs, with the jumpers but not when connected, the fan relay is the most likely problem.

3. If fan operates but a high current draw is suspected continue with the following ammeter TESTING.

4. Disconnect the electrical connector from the cooling fan.

5. Using an ammeter and jumper wires, connect the fan motor in series with the battery and ammeter. With the fan running, check the ammeter reading, it should be 3.4-5.0 amps; if not, replace the motor.

6. Reconnect the fan's electrical connector. Start the engine, allow it to reach temperatures above 194°F and confirm that the fan runs. If the fan doesn't run, replace the temperature switch.



Ok, Now we will move on to the next possible issue. The water pump. ok, due to the fact that your pump is driven by the drive belt, you will need to start the engine and listen for bad bearing, using a mechanic's Stethoscope or rubber tubing.

* Place the stethoscope or hose on the bearing or pump shaft.
* If a louder than normal noise is heard, the bearing is defective.

Replace the pump in this case.

You will also notice leakage around the pump housing if the seal has failed as well. this will strain the impeller and, ruin the pump.

Now. the last area of concern will be the thermostat. this is the most common issue that will inflict overheating in many vehicles. The thermostat is used to control the flow of engine coolant. When the engine is cold, the thermostat is closed to prevent coolant from circulating through the engine. As the engine begins to warm up, the thermostat opens to allow the coolant to flow through the radiator and cool the engine to its normal operating temperature. Fuel economy and engine durability is increased when operated at normal operating temperature.


There are several ways to test the opening temperature of a thermostat.

One method does not require that the thermostat be removed from the engine.

* Remove the radiator pressure cap from a cool radiator and insert a thermometer into the coolant.
* Start the engine and let it warm up. Watch the thermometer and the surface of the coolant.
* When the coolant begins to flow, this indicates the thermostat has started to open.
* The reading on the thermometer indicates the opening temperature of the thermostat.
* If the engine is cold and coolant circulates, this indicates the thermostat is stuck open and must be replaced.

The other way to test a thermostat is to remove it.

* Suspend the thermostat completely submerged in a small container of water so it does not touch the bottom.
* Place a thermometer in the water so it does not touch the container and only measures water temperature.
* Heat the water.
* When the thermostat valve barely begins to open, read the thermometer. This is the opening temperature of this particular thermostat.
* If the valve stays open after the thermostat is removed from the water, the thermostat is defective and must be replaced.
* Several types of commercial testers are available. When using such a tester, be sure to follow the manufacturer's instructions.
* Markings on the thermostat normally indicate which end should face toward the radiator. Regardless of the markings, the sensored end must always be installed toward the engine.
* When replacing the thermostat, also replace the gasket that seals the thermostat in place and is positioned between the water outlet casting and the engine block.

* Generally, these gaskets are made of a composition fiber material and are die-cut to match the thermostat opening and mounting bolt configuration of the water outlet.
* Thermostat gaskets generally come with or without an adhesive backing. The adhesive backing of gaskets holds the thermostat securely centered in the mounting flange, leaving both hands of the technician free to align and bolt the thermostat securely in place.

The pcv is on the drivers side valve cover. It's an orifice type system and only needs to be checked for blockage which usually don't happen. If you can see through it don't replace it.

well the air pump is used to reduce emmissions it sends fresh air into the cylinder to help reduce the exhaust gases.....if your looking for more power you should be fine........have fun and good luck

average 195-225 F would be the normal range, this would hot cold weather and varied types of driving

I doubt it....It could be a totally worn out engine. Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

You will now have to check the fuel system!

Try cleaning the EGR valve or just replacing it and replace the PCV valve as well.

At my shop we have seen this happen often. We take a hacksaw that extends the blade a couple inches out from it.
Carefully saw two opposite sides of the broken piece to the point of where the threads just begin to surface. Don't go too far! Then take a firm pick and gently pry out the two pieces.
We then go to our local plumbing store and get a threaded nipple and clamp a new heater hose to it.
Apply some teflon tape to the nipple

spray water on belts and see if noise gon

replace the spark plug wire set.