how to replace bypass hose on nissan Quest

By pass hose is very challenging to replace because it is located in a difficult place to reach, especially where it connects to the water pump. The replacement process can be time consuming and frustrating, but with some patience, the right tools and a game plan, it can be done.

Unbolt the A/C compressor from the bracket and move it to the side. (It may not be necessary to completely disconnect the compressor.)

Unbolt the alternator from the bracket and move it to the side. (It may not be necessary to completely disconnect the alternator.)

Unbolt the bracket from the engine block and move it to the side.

Using the torsion spring hose tool, spring the two hose clamps, remove the bypass hose, and replace it with the new one. Replace the spring-type hose clamps with screw-type clamps.

Jack up the front of the car and lower it onto jack stands below the two front tires. Place a drain pan under the radiator drain valve. Loosen the valve and partially drain the radiator so the coolant level reaches just below the bypass hose.

Use a screwdriver to loosen the bypass hose clamps and remove the hose. In some cases, the bypass plumbing uses a pipe instead of a rubber hose. These pipes, or hoses, are located near the thermostat housing. Follow the upper radiator hose to the entry port on the engine. Usually the thermostat is located inside the engine, in a housing where the upper hose is attached. The bypass hose is below the housing. The bypass hose is always much smaller than the radiator hose.

Install a new hose and tighten the clamps. If the bypass circuit uses a pipe, inspect the old pipe. These normally rust and routine replacement is vital to maintain the integrity of the cooling system. Tighten the radiator drain valve.

Lower the car from the jack stands and refill the radiator with coolant. Start the vehicle. Allow it to reach operating temperature and check for coolant leaks. Shut off the engine and allow it to cool. Recheck the coolant level and refill as needed.

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All you need to do is to buy a new hose, loosen the hose clamps on the ends of the existing hose, pull the old hose off the spigots (or cut it off with an exacto knife or razor blade if it will not move); clean and scrape off all traces of old hose material from the spigots, slide the new hose into position, and firmly tighten the hose clamps (use new worm gear hose clamps if the old ones are the wire type). There will probably be some coolant leakage while the hose is off. The mess from this can be minimized if you open the drain valve on the bottom of the radiator and drain the coolant into a container before removing the hose. After the new hose is installed, turn the heater temperature control to hot (in order to allow coolant to flow through and fill the heater), remove the radiator filler cap and pour a mixture of equal quantities of distilled water and new coolant directly into the radiator, until the radiator is filled to overflowing. Then start the motor; the coolant level will drop when the motor runs; so while the motor is running, refill the radiator to overflowing again, and install and tighten the radiator cap before shutting the motor off. This should be done before the motor has run for more than about 3 minutes; as it will begin to heat and expand the coolant after that. It is often a good idea to replace the heater hoses, and possibly also the main radiator hoses, when the bypass hose goes bad. So I would carefully inspect all the hoses and their clamps before deciding what to buy. The coolant overflow reservoir should also be filled to the proper level with the same 50-50 mixture of coolant and distilled water at this time.


The day after doing this repair; remove the radiator cap again, and check and refill as necessary the coolant level in the radiator with the motor cold and idling . There is often trapped air that will come out of the system, which will cause the coolant level to drop. Only after the air has all come out of the system can the level be trusted in the overflow reservoir. If the level was significantly low, recheck it again on one or more subsequent days; until it stops dropping; or until the source of any additional leaks is discovered and repaired.

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You'll have to remove the plate in the back (held on by four bolts) to access the camshaft seals and bypass hose. Take the cam sprockets off first, impact is a must for this (unless you have the crankshaft pulley on still). I'd recommend replacing the bypass (small 90 degree) coolant hose with the Nissan part.

The bypass hose connects to a body where the upper radiator hose connects. There are 2 or 4 bolts holding this said body on to the block... Get the gasket and seal out of it.