Question about 1999 Nissan Altima
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Posted on Jan 02, 2017
Dear Guest: If you have some reasonable mechanical aptitude, it is a simple task on this engine to do.
The thermostat is located near the front to the engine (the side closest to the belts) and on the side where the radiator is.
Follow the top radiator hose to the engine and you will have found the thermostat housing.
1. Make sure the engine is cool before doing this job.
2. Get a drain pan and drain the coolant from the radiator. The drain **** for the radiator is located at the bottom of the radiator. Some have an end which can be turned without tools and others require a flat screw driver to unscrew the fitting from the bottom of the radiator. Make sure you remove the radiator cap, as it will drain much faster. Once drained, put the drain **** back into the radiator. Be careful and DO NOT OVER TIGHTEN IT! It will snap off in the radiator!
3. Release the hose clamp which secures the hose to the thermostat housing and then grasp the hose at the neck where the clamp was and try to rotate the hose on the housing. DO NOT try to just pull the hose off. Break it loose first by rotating it on the housing. If it is stuck, get a small screw driver and carefully, slide it in between the hose and the housing, working it around until you can rotate the hose. At that point you can remove the hose and push it off to the side or take it loose at the radiator as well. CAUTION!!!!! the radiator tanks are plastic and will break if you are not careful!
4. There are 3 bolts which retain the housing to the cylinder head.
Typically the bolt head size is a 10mm. Using a 10mm socket, rotate the bolts in a counter clockwise direction, removing all three bolts. There are some that did use a 12 mm bolt head size. Most of the time the housing will just come loose. Sometimes, it will stick. If so, a light tap will break it loose. Pay attention as to how the thermostat is positioned in the cylinder head prior to removing it. Most of the time it will pop out easily or you can easily pry it out with a small screw driver. CAUTION!!!!
Do not damage the mating surface where the gasket seals.
Carefully clean the old gasket off. A single edge razor works fine.
5. The thermostat has a top and a bottom. If you look closely, you will see a place in the outer parameter of the thermostat where there is a small hole, often with a little metal tab which projects through the other side and is able to jiggle some. This is a small bleeder to help bleed the air trapped in the system when it is installed. This part of the thermostat must be at the 12:00 position.
Additionally, make sure the part with the hoop is sticking out toward you. The cylinder head has been machined to allow the thermostat to fit flush with it when installed properly.
6. Clean the old gasket from the thermostat housing. Nissan utilizes a liquid gasket sealer (silicon) which you apply a "SMALL" bead around the water inlet (the cylinder head side), let the sealer skin lightly and then put the housing in place making sure that the thermostat had remained seated during the installation. If it had come loose and you try to tighten the bolts, you will crack the thermostat housing.
7. When you tighten the thermostat housing bolts, there is a torque specification however most people don't have torque wrenches which measure in inch pounds. For those who have a torque wrench, 10mm bolts:56.4-66 inch lbs, 12mm bolts 12-14 ft lbs.
I have found that the easiest way to keep from over tightening the bolts is to grab the ratchet from the head and tighten the bolts because you don't have the leverage at that point.
8. Let the silicon dry for 10 minutes and and then fill the system back up with coolant. Reattach the hose and clamp being careful not to over tighten the hose clamp.
If you are replacing it, not more than a 50/50 mix. There is no special bleeding procedure Nissan has for this car. Just fill the radiator with coolant, turn the heater inside the car to the heat position to allow coolant flow into it as well, because it too is part of the cooling system in terms of coolant capacity. I usually fill the radiator until it shows 1/2 way up the tank. As the engine warms up,prior to the thermostat opening, more often than not, the coolant level will rise dramatically before it drops. Once the thermostats has opened top the system off, put the cap on and let it run for a while and watch for leaks. Take the car on a short loop and then recheck for leaks again. If everything has gone well, the temperature will read normal and no coolant will be leaking.
Hopefully this should be sufficient to answer your question.
Posted on Apr 05, 2009
thermostat should be at the end of the top radiator hose on the engine side.drain radiator most of the way to prevent coolant gushing out when you remove hose.unbolt housing replace thermostat.hope this helps
Posted on Aug 17, 2009
yes,have suggestion.leaking coolant into the passeger side floorboard? film on the windsheild at anytime? suggest a bad heater core. or this,heater core stopped up.needs to be flushed.flush radiator with a common flush found at autozone,advance autoparts stores.or any other auto parts stores. remove your heater core hoses on the firewall[2 small hoses that go from the motor through the firewall to the heater core itself] flush the heater core there manually.push your water hose to the passenger side there and turn hose 'on' and watch the flow out the other side.[both hoses on the firewall will have to be off[or disconnected]to do this properly. your problems here,and since you've replaced the thermostats twice,suggest that this is your issue. thank you for choosing fixya.com
Posted on Jan 28, 2011
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