Can I bypass the air system to fill air manually

There could be a few possible causes for the rear heater not blowing hot air in your 2003 Chevrolet ASTRO van. Here are a few things you could check:

1. Make sure that the rear heater control valve is fully open. This valve is located near the heater core and controls the flow of coolant to the rear heater.
2. Check the coolant level in the radiator. If the coolant level is low, the heater may not be able to produce hot air.
3. Check for any leaks in the coolant system. If the system is leaking, it may not have enough coolant to produce hot air.
4. Check the thermostat. If the thermostat is stuck closed, it may not be allowing enough coolant to flow through the system to produce hot air.

If these steps do not help, it is possible that there is a problem with the heater core itself, or with other components of the heating system. It may be necessary to have a mechanic diagnose and repair the issue.

When running the engine to bleed air was the cap on the rad fill hole? It should be so the coolant system builds up the required pressure, may have to repeat this process a couple of times, after engine has cooled,the expansion bottle is the better place to refill the coolant

Removal & Installation

1. Before servicing the vehicle, refer to the Precautions section.
2. Drain the coolant.
3. Remove or disconnect the following:
   
   Negative battery cable

Upper fill panel, if equipped
AIR injection control valve, if equipped
Air cleaner
Oil level indicator tube nut, if necessary
Water pump belt cover
Water pump drive beltLower radiator hose
Thermostat bypass hose from the coolant inlet housing
Water pump cover

Remove the water pump by rotating it clockwise using special Tool J 38816-1A (water pump remover/installer).
To install:
Install the water pump with a new O-ring, by turning it counterclockwise using the special tool, until it stops. Torque the water pump to 73 ft. lbs. (100 Nm).

Install or connect the following:

Water pump cover. Torque the bolts to 89 inch lbs. (10 Nm).
Lower radiator hose
Thermostat bypass hose to the coolant inlet housing
Water pump drive belt
Water pump belt cover
Oil level indicator tube nut, if necessary
Air cleaner
AIR injection control valve, if equipped
Upper fill panel, if equipped
Negative battery cable

• Refill and bleed the cooling system.

Run the engine and check for leaks.

Could be that your heater matrix is blocked or has air in the system

Thermostat? engine cooling?
2 engines, here, LYA adn LY7.
nobody here posts engine, why do that?
so ill post only for 1.
the LA1
here are the steps.
NO FSM Sux huh? nor an alldata.com account, why not that? 15 bucks?


STAT out.
Remove the air cleaner and duct assembly. Refer to Air Cleaner Assembly Replacement in Engine Controls - 3.4L.

Drain the coolant until the coolant level is below the thermostat. Refer to Cooling System Draining and Filling (Refer To List 1) .

Remove the crossover exhaust pipe. Refer to Exhaust Crossover Pipe Replacement (Refer To List 2) in Engine Exhaust.

Remove the radiator hose from the thermostat housing.

Remove the thermostat housing bolts and clean any sealer from the bolt threads.

Remove the thermostat housing and gasket.
remove STAT
next is crossover page.

Disconnect the battery ground (negative) cable. Refer to Battery Negative Cable Disconnection and Connection (Refer To List 1) in Engine Electrical.

Remove the throttle body air inlet duct.

Drain the coolant from the cooling system. Refer to Cooling System Draining and Filling (Refer To List 2) in Engine Cooling.

Remove the inlet radiator hose from the engine. Refer to Radiator Inlet Hose Replacement (Refer To List 3) in Engine Cooling.

Remove the thermostat bypass pipe. Refer to Thermostat Bypass Pipes Replacement in Engine Cooling.



Remove the exhaust crossover heat shield bolts.

Remove the exhaust crossover heat shield.

1. Remove the exhaust crossover pipe studs/nuts.
2. Remove the exhaust crossover pipe.

end , remove.

now the bypass pipe FWD cars SUCK

1. Disconnect the left engine mount strut from the engine.
2. Remove the heater hose from the bypass pipe.
3. Remove the thermostat bypass pipe to throttle body nut.
4. Use the J 38185 in order to remove the thermostat bypass pipe hose clamps (1,5).
5. Remove the thermostat bypass pipe to cylinder head nut (3).
6. Remove the thermostat bypass pipe bolt (4).
7. Remove the thermostat bypass pipe hose.
8. Remove the thermostat bypass pipe.

sigh.....
why not log in to alldata.com
read the page then ask ques tons that are not clear.
and next time post the engine type.
above is just 1 engine.

Engine or hydraulic system overheating Coolant system low on coolant in 6020, 6030, 6030 Premium, 7020, 7030 and
7030 Premium Series Tractors.

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Symptoms
After several hours of work, warning system indicates hot engine coolant or hot hydraulic oil.
Situation or Problem
Coolant level in reservoir is between the "MIN" and "MAX" range but engine or hydraulic system is overheating.
Summary
Air is entering cooling system, hindering coolant flow. Check coolant level. Fill to the "MAX" line on the coolant reservoir.
Bleeding Cooling System:
The bleed valve (see Operator's Manual for location) on the radiator must be closed when the tractor is operating. Open the valve when coolant is drained or filled. If the bleed valve is left open, coolant will internally bypass between the low temperature circuit and engine high temperature circuit causing overheating. When bleeding the system, open the bleed valve and run the engine with no load for 5 minutes at 1700 rpm. Then shut engine off for 5 to 10 minutes before closing the drain valve. Check the coolant level. If level is below the "MAX" fill line, repeat this procedure until coolant level stays at the "MAX" line.

Sometimes yes, you will need to jump the cycling switch or also called the low cut off switch, this is located on the filter dryer,a quick note, if the system has air or moisture in it and you charge it you may get cold air to blow but will cause damage to the compressor over time and cause it to go bad. the correct way is the evacuate the system and then vacuum it down and then fill with some oil and fill with the correct amount of freon,without gauges its hard to know if you are adding the correct amount and this causes damage over time, just because its blowing cold doesnt mean it fine, good day, hope this helps.

I'm not sure the MK4 1.9TDI has a primmer actuator like the the old models did. This primes the fuel system removing air inside the system. I know there is a procedure in your case to prime the system which will require cracking open a valve and bypassing the fuel pump relay to operate manually filling the system with diesel and ridding the air inside.

You may have air trapped in the system or rust plugging up the rear heater core. core, if it is just an air problem do this: Fill the radiator and the coolant recovery tank as full as possible, then raise the front of van as high as you can with a floor jack, run the engine until it is at normal operating temperature, let it cool down, running water over the radiator speeds this up, this should purge the air out of te system and cure your issue with the rear heater. Make sure you have a good radiator cap if it is the original one replace it. If the system still has no flow to the rear pull out the rear heater core and flush it out or replace it.