Jump to content

Water pump

Recommended Posts

  • Replies 10
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Cars that are moving don't need much fan at all. Vehicle speed pushes plenty of air through the rad. When the engine is cold is another time it isn't needed. The clutch has built in slip and is limited to about 1,500 RPMs no matter what the engine is turning. If it senses being over heated, the clutch increases the friction and the fan speed will increase to about 2,300 RPMs. This saves energy moving masses of air that is not needed.

Link to comment

When the engine is off you should be able to turn the fan with your finger. It should be firm and is not loose enough to spin freely.


The fan does not stop with the engine running it only reaches a maximum speed of about 1,500 RPMs. If the engine revs higher it remains the same. The clutch is filled with a special silicon oil that provides the slippage. If it leaks out the fan will slip severely and the engine can over heat. They have also been known to seize and spin up higher. In this case they sound like an F-18 taking off.

Link to comment

There are variations in the bolt spacing on the plastic fan blades where they bolt to the water pump. I know of three different sizes, but there may be more. If you get a non-clutch water pump there is a pretty good chance you will need to get a different plastic fan. Not a problem if you can find one at a wrecking yard or have time to advertise in the Classifieds here on Ratsun . Some of the online parts sources and autoparts stores will give a measurement for the fan bolt hole spacing. It seems like some parts catalogs show water pumps with or without AC and those may have different fan sizes. I can't quite remember. So when you shop for a new pump you should pay attention to the size of the fan you have.


On my '72 510 with L20b, I had to remove the radiator to change the water pump. Nissan cleverly uses one long bolt which is captive behind the water pump pulley, so you need quite a bit of room to get the pump away from the front cover. I have a feeling you will need to pull the radiator on your 510, but look at your new pump or a pic in an online catalog and you will see the bolt I'm talking about and decide. Pulling the radiator is pretty easy except the radiator hoses are usually stuck on really tight. Be careful about just trying to pull them off as you can crack the solder joint where the hose neck attaches to the radiator. It is better to run a small screwdriver in between the old hose and the neck to free up the hose. I suspect Harbor Freight sells a special tool for this that looks like a cotter pin awl with a much longer nose. If your radiator hoses are very many years old, buy new ones and just cut the old ones to get them off. You will be much happier replacing the hoses now than doing it along side the road this summer! :D



Link to comment

I have a 78 datsun 510 and the engine is an l20b. I need a new water pump but I can't fine one that does not have a clutch. And since I don't have the car I have no idea what the pump looks like. Someone help me out?


You need to find out if you do, or do not, need the pump with the clutch. If you don't have the car, perhaps someone told you the pump is bad and needs replacing before you drive it? If it's the original pump it should have the clutch also. BTW the clutch is NOT removable and is pressed on.


If replacing any hoses, as Len suggests, I find slitting them lengthwise with a box cutter worked better than a screwdriver. Then just peel them off.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.