BS5495E

Pump the pressure up to 20 to 21 psi and check to see if pressure holds. Check for leaks.
Wait for 20 minutes and Check whether the pressure regulator gauge shows a decrease in pressure. If there
is a decrease in pressure a leak check must be performed (see leak checking below).

Figure 11 - Pressure Check

NOTE

A decrease in the gauge pressure indicates a leak in the engine coolant system. If there is no decrease in
pressure indicated on the gauge, the engine cooling system is good and posable air was trapped in the system.

Leak Checking
Leak test with engine coolant empty.
If the gauge shows a decrease in pressure, there is a possible leak in the system. You will need to
pressurize the engine cooling system with air, to the same pressure you used to check for leaks. Spray the
cooling system with the use of a spray bottle with soap-water solution and check for leaks.

Leak test with engine coolant.
For system with coolant still in the system look for a coolant leaking from the fitting and hose’s.

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Figure 12 - Leak Testing

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Inspect all of the welded joints on the copper pipes. Inspect all hose clamps. In both cases, look for leaks
and seepage. Below reference shows the visual inspection of solder joints.

BLUE CIRCLE: NOVA BUS WELDING
RED CIRCLE: ORISKANY WELDING

1.18.

BS5495E

Figure 13 - Inspection of Welded Joints
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No. std:
Rev.:
Date:
Gr:
20

Nova Bus Standard
Assembly Standard:

Quality Criteria :

X

Drawing Ref.:

BS5495E

AVT Ref:

STD0291
00
2023-02-13
General

Supplier Spec.:

Title:

Visual inspection of solder joints.

Description:

When the joint is properly made, filler metal will be drawn into the joint and a continuous
seam of filler metal will be visible completely around the joint. Evidence of cracks,
voids, bubbles or lack of filler metal in the joint shall be rejected.

Accepted

Rejected

Reference : AVT-0277
(In case of divergence, the document referenced on the BOM takes precedence over the quality standard )

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1.19.
1.20.
1.21.

BS5495E

If coolant leak is detected move to level 2 Removal of Pipes.
Tighten the clamps on the flexible hoses on the roof unit.
Turn the vehicle engine off.

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BS5495E

LEVEL 2 : REMOVAL OF PIPES
1.22.

Depressurize the cooling system by opening the surge tank cap, located in the engine compartment.

CAUTION

Wait until the engine coolant temperature is below 120°F (50°C) before removing the surge tank cap. Failure
to do so could result in injuries from heated engine coolant spray.
1.23.

Partially drain the passenger compartment heating circuit.

CAUTION

Avoid prolonged and repeated skin contact with used coolant. Such contact can cause skin disorders or
other injury.

SUPPLY

SOLENOID VALVE
ON FLOOR
HEATING RETURN

RETURN

TO ENGINE
TO / FROM
ROOF UNIT

STREET SIDE
CONVECTOR
FROM AUXILIARY
HEATING UNIT

DRAIN VALVE

CURB SIDE
CONVECTOR

FRONT DEFROSTER

Figure 14 - Typical HV System Flow Chart

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1.24.
1.25.
1.26.
1.27.

BS5495E

Close the cut-off valve at the auxiliary heating unit output and the return valve of the bus compartment to cut
off the compartment circuit from the engine circuit.
Place the heat control lever of the front ventilation control panel at the extreme right position to open the
front defroster butterfly valve.
Open the main drain valve, located at the front center of the bus, next to the defroster. Have a recovery
container handy.
Remove the protective panels at the bottom of the walls. Open the two small drain valves located in the
middle of the bus, at the floor convectors intake; one is on the right and one is on the left.

Figure 15 - Drain Valve located on Street side

Figure 16 - Drain Valve located on Curb side

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BS5495E

NOTE

Before proceeding, make sure a container is available for recovering the liquids that escape from the valve.
1.28.
1.29.
1.30.
1.31.

Release the pressure from heating control valve.
Open the street side baselight/ceiling panel to access the valve.
Disconnect the elbow connector of the supply cable from the pilot valve.
Disconnect the pneumatic hose from the valve.

1.32.
1.33.
1.34.

Loosen the fittings on both sides of the valve and remove the valve.
Remove the loom and tube insulation from the heating pipes.
Disconnect and remove the pipes.

Figure 17 - Removal of Damaged Pipes

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BS5495E

INSTALLATION OF PIPES
1.35.

The Heating pipes must be cut squarely and cleanly.

1.36.
1.37.

Clean the contact surfaces of parts to be assembled with an abrasive pad.
Welding paste N25165 must be applied with a brush and coat the male and female surfaces of parts to be
assembled.

Figure 18 - Cleaning the Pipe Contact surface

1.38.

Connect the supply pipe N85930 and return pipe N92370 to the heating pipe of engine compartment.

N85930

N92370

ENGINE
COMPARTMENT
PIPE

Figure 19 - Installation of Pipes
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1.39.

BS5495E

1.40.

After having placed pipes to be joined in their definitive positions, the parts to be assembled are heated evenly
with a continuous motion of the flame or maintaining in place the soldering gun.
Use acetylene / MAPP torch or an electric soldering gun.

1.41.
1.42.

Heat until the tin begins to fuse on the surface of pipes to be joined.
The filler metal/ welding wire N25166 must flow easily in the joint by capillary effect.

Figure 20 - Soldering the Pipes with Soldering gun

NOTE

It is the heat of the pipe that melts the filler alloy. The operation must continue until the joint is filled. Do not
heat when the filler metal is applied.
1.43.
1.44.

Cool the assembly with water 1 to 2 minutes after the required quantity of filler metal/ welding wire is applied,
then clean with water to remove any excess flux/ welding paste.
Add loom N43021 to the wires and secure with cable tie G5007995.

1.45.
1.46.

Add insulation tube N20379 for the heating pipes and secure with cable tie G5007995.
Repeat the steps 1.26 to 1.33 for the installation of other heating pipes.

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1.47.
1.48.

BS5495E

Connect the supply pipe N100293 and return pipe N100099. Add insulation tube N20379 for the pipes and
secure with cable tie G5007995.
Add Thread loctite N37086 to connectors N79131 to connect the valve with the support bracket and mount
the cable tie G5007996.

N100293
N100099

Figure 21 - Installation of Pipes

1.49.
1.50.
1.51.
1.52.

Connect the heat pipes N100311 and N100316 to the front defroster pipes and add insulation tube N20379.
Add insulation tube N20378 for the heating pipes.
Add loom R015045 for the heating pipes.
Add loom N43021 for the heating pipes.

N100316

FRONT
DEFROSTER PIPES

N100311

Figure 22 - Installation of Pipes to Front Defroster

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BS5495E

N100316

N100293

N100311

N100099
N85930

N92370

Figure 23 - View of Installed Pipes

1.53.

Connect the pneumatic hose to the valve.

1.54.
1.55.
1.56.

Connect the elbow connector of the valve’s wiring harness to the pilot valve.
Reopen all coolant isolation valves.
After all repairs are completed perform leak check before adding coolant. Perform steps 1.7 to 1.16 starting
on page 5.

1.57.
1.58.

Return air pressure to the vehicle.
Fill the engine coolant circuit.
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BS5495E

ENGINE COOLANT FILLING PROCEDURE
1.59.

Under the vehicle, place a drain pan below the coolant overflow tank and drain hose.

1.60.
1.61.

Open the drain valve on the coolant overflow tank.
Set the engine fill valve to the front-back position (the handle should be perpendicular to the manifold label
plate).
Connect the filling hose to the quick-connect engine fill port.
Begin coolant filling until the FULL COLD light turns ON or coolant begin to flow in to the drain pan under
the bus.

1.62.
1.63.

VALVE

COOLANT
OVERFLOW
TANK

CLOSED
VALVE HANDLE
POSITION

DRAIN VALVE

DRAIN HOSE

QUICK-CONNECT
ENGINE FILL
PORT

PERPENDICULAR
(OPEN) VALVE
HANDLE
POSITION

Figure 24 - Coolant Overflow Tank and Coolant Fill Panel

1.64.

Vehicle ready for the service.
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