Jump to content
slim_jimmy7

Datsun 510 Cooling Issue

Recommended Posts

Self learned car guy with limited knowledge here so bear with me.  Prepare for the word vomit.

 

I live in Iowa so this time of year a functioning heating and radiator cooling system is very important. 37 degrees this morning, 76 at noon. I purchased this vehicle from California, and by and large it's a good vehicle. 510 4-door automatic 1972(hoping at some point to put in a manual).  No engine mods as far as I know.

 

I drove it a few times over the summer on trips of 30 minutes or so. Each time I would drive the engine temp would slowly creep up to almost full hot.  The heater core was deleted when I got it. I would reach my destination just in time and set there for a few hours before making my trip back home.

 

If I squeezed the top hose a few times before startup, the car stays cooler longer, I will be able to drive an hour uninterrupted before the temp gets too hot. If I stay at 55mph, my temp will not raise, anything higher and it rises.  Transmission cooler hoses leak when under pressure, level looks good on the transmission though.

 

Got a new rebuilt carb and adjusted (made sure not too much air flow), flushed the radiator 2x.  Took radiator out/flushed it, replaced water pump, flushed the engine (water flowed). No little bubbles in the coolant, oil doesn't change color.

 

A lot of rust and lime was inside the radiator when I got it out, but temperature readings on lower and upper hoses seemed to show the cooling was happening. If it is 180-200 on top hose, 120-130 on bottom hose.

 

Replaced thermostat, took thermostat out to check for maybe a blockage behind the thermostat, same result. Re added the heater core recently.

 

My test trips have a few stops in the country, 4 miles to the 1st stop the car will run just below the "E" in TEMP, no matter what speed I go.  As soon as I slow down and speed back up the temp starts rising past the P, when I stop to check the temp with a laser thermometer the temp is around 200-215 or so on top hose.  And engine block is warmer, lower hose may creep up to 140, but that is it.

 

Since adding the heater core, my trip to the location will have heat for defrost on the way up, but on the way back the heater is cold.  When idling the temperature is good, in fact if it gets warm I can stop at a corner and keep it there for a few minutes at idle and it will cool off.

 

I'm totally lost, any advice?

Share this post


Link to post

You check your timing? What do color are your spark plugs? Is tstat on backwards, what kind of stat you have? Stay away from stant.

  • Like 2

Share this post


Link to post

Self learned car guy with limited knowledge here so bear with me.  Prepare for the word vomit.

 

I live in Iowa so this time of year a functioning heating and radiator cooling system is very important. 37 degrees this morning, 76 at noon. I purchased this vehicle from California, and by and large it's a good vehicle. 510 4-door automatic 1972(hoping at some point to put in a manual).  No engine mods as far as I know.

 

I drove it a few times over the summer on trips of 30 minutes or so. Each time I would drive the engine temp would slowly creep up to almost full hot.  The heater core was deleted when I got it. I would reach my destination just in time and set there for a few hours before making my trip back home.

 

If I squeezed the top hose a few times before startup, the car stays cooler longer, I will be able to drive an hour uninterrupted before the temp gets too hot. If I stay at 55mph, my temp will not raise, anything higher and it rises.  Transmission cooler hoses leak when under pressure, level looks good on the transmission though.

 

Got a new rebuilt carb and adjusted (made sure not too much air flow), flushed the radiator 2x.  Took radiator out/flushed it, replaced water pump, flushed the engine (water flowed). No little bubbles in the coolant, oil doesn't change color.

 

A lot of rust and lime was inside the radiator when I got it out, but temperature readings on lower and upper hoses seemed to show the cooling was happening. If it is 180-200 on top hose, 120-130 on bottom hose.

 

Replaced thermostat, took thermostat out to check for maybe a blockage behind the thermostat, same result. Re added the heater core recently.

 

My test trips have a few stops in the country, 4 miles to the 1st stop the car will run just below the "E" in TEMP, no matter what speed I go.  As soon as I slow down and speed back up the temp starts rising past the P, when I stop to check the temp with a laser thermometer the temp is around 200-215 or so on top hose.  And engine block is warmer, lower hose may creep up to 140, but that is it.

 

Since adding the heater core, my trip to the location will have heat for defrost on the way up, but on the way back the heater is cold.  When idling the temperature is good, in fact if it gets warm I can stop at a corner and keep it there for a few minutes at idle and it will cool off.

 

I'm totally lost, any advice?

 

 

I had similar issues with overheating with a stock radiator and L16. I flushed the radiator multiple times. Used muriatic acid.. use radiator flush chemicals. Flowed water in both directions. End result, rust, and still overheating.

 

I would pull the radiator, take to a radiator shop and have them boil it. They will be able to clean and test it for you. It's more than likely just a few of the rows are plugged with debris that won't come out without some persuasion.

 

You can take your hand or temp gun and hit it on multiple spots on the radiator. You might find that some spots are much cooler than others. What would signify a blockage.

 

Do you have a fan clutch? This could also be bad and causing similar issues.

  • Like 1

Share this post


Link to post

I would bet it is a stant, plugs look OK, slightly brownish.  I will recheck the timing, it idles rough under load yet, if it's in park or neutral it's perfect, but if I am at a stop light it's rough.

Share this post


Link to post

Forgot to mention that ur radiator maybe plugged up in certain areas.

  • Like 1

Share this post


Link to post

I had similar issues with overheating with a stock radiator and L16. I flushed the radiator multiple times. Used muriatic acid.. use radiator flush chemicals. Flowed water in both directions. End result, rust, and still overheating.

 

I would pull the radiator, take to a radiator shop and have them boil it. They will be able to clean and test it for you. It's more than likely just a few of the rows are plugged with debris that won't come out without some persuasion.

 

You can take your hand or temp gun and hit it on multiple spots on the radiator. You might find that some spots are much cooler than others. What would signify a blockage.

 

Do you have a fan clutch? This could also be bad and causing similar issues.

 

 

No fan clutch, when I tipped the radiator after taking it out, it was like gravel rolling around.

Share this post


Link to post

Is it smoking a lot white smoke? Hopefully ur head gasket didn't fail. Check your oil on dipstick if it looks like chocolate malt, then coolant and oil got mix.

  • Like 1

Share this post


Link to post

Got an idea...drive it w out tstat, if it overheats then likelihood its the rad.

  • Like 2

Share this post


Link to post

When the heater is cold on the way home feel the heater hoses under the hood... hot??? Only low water level can prevent the heater being hot. Check the heater box for mice nests that will prevent proper air flow through the heater. Under the wipers under the cowl is where the make up air gets in. Take it off and clear any rotten leaves, pine needles and maple keys away that might reduce air flow to the heater. Check the the heater door flaps are adjusted and you are getting full heat. Check that the heater water valve opens fully to let in the hot water.

 

 

Are you constantly adding coolant? Every week or even every day or two????

 

Check the lower rad hose is in good shape. Rev the engine while looking at it. Does it collapse from pump suction? Rad hoses rot from the inside out and may look OK but are soft to the touch. A soft hose will collapse and restrict flow at highway speeds but work in town.

 

Do you have a small by pass hose from the thermostat housing down across the front of the engine to the lower rad hose where it enters the engine? Has someone removed it or plugged the hoses??? It probably does but if not, take your thermostat out and drill a 1/16" hole in the outer edge.

 

If you can turn the fan by hand without turning the engine, the belt is probably too loose.

 

 

 

Drain the coolant into a container. Take the heater hoses off the head and the front of the engine and using a garden hose force water through the heater core in both directions. Set the heater controls to HOT. Collect this water and see if sediment and crap in it.

 

While rad is empty, remove and with cap on and face down fill 50/50 with CLR and let sit over night. CLR will dissolve hard water scale. I did this for 3 days with no ill effect. There was a small amount of scale but my water is very soft. Scale reduces flow and heat transfer.

 

ALWAYS run a mixture of antifreeze/coolant mix suitable for the lowest temperature expected.

  • Like 2

Share this post


Link to post

Hopefully I replied to all of these:

 

The heater core was repaired at a radiator repair shop after I took it out and cleaned it all up, also sent my valve off to a cool guy in Bend, OR who made it like new.  The collapsing lower hose thought makes a lot of sense with what I am experiencing.  I may try that with a new radiator or have the radiator sent off to be repaired

 

Oil is good color, no white smoke, sometimes it'll smoke blue on startup.  I did take out the thermostat, and it did still heat up.

  • Like 1

Share this post


Link to post

$10 for CLR to clean the scale out.

 

Put thermostat back in and the temp won't jump around so much.

 

 

Does it need topping up all the time?

  • Like 1

Share this post


Link to post

Hopefully I replied to all of these:

 

The heater core was repaired at a radiator repair shop after I took it out and cleaned it all up, also sent my valve off to a cool guy in Bend, OR who made it like new.  The collapsing lower hose thought makes a lot of sense with what I am experiencing.  I may try that with a new radiator or have the radiator sent off to be repaired

 

Oil is good color, no white smoke, sometimes it'll smoke blue on startup.  I did take out the thermostat, and it did still heat up.

...you mean it still overheated? Yeh something is blocking flow or hose collapsing
  • Like 1

Share this post


Link to post

Forgot to say, take out the hose and see if its in good shape

  • Like 1

Share this post


Link to post

So last night I drove to the football game which is around 30 minutes away. I went to the autocrats store and grabbed three hose clamps and put them on the upper and lower hoses in areas I thought it would be prone to collapsing.

 

Perfect temperature and had defrost the whole way!  So guess I will need some new upper and lower hoses.  Thank you for your quick responses datsunmike, draker, and racerx.  Now I can start moving forward with this thing.

 

$10 for CLR to clean the scale out.

 

Put thermostat back in and the temp won't jump around so much.

 

 

Does it need topping up all the time?

 

Does that eat gaskets or are you talking about taking the radiator out and doing it outside the car?

Share this post


Link to post

While rad is empty, remove and with cap on and face down fill 50/50 with CLR and let sit over night. CLR will dissolve hard water scale. I did this for 3 days with no ill effect. There was a small amount of scale but my water is very soft. Scale reduces flow and heat transfer.

You have to drain to change the hoses anyway so 4 bolts and lift out. I let mine sit for three days because I couldn't get back to it. What scale there was fizzed and dissolved away clean.

 

Buy Distilled water if possible or if you already have it filled use only distilled water for top ups. Over years the water boils away concentrating the dissolved minerals in it.

 

Another good idea to reduce rad top ups is a coolant recovery system. You need the special rad cap some hose and a small sealed container. I just got mine from a 720 truck. When the rad water expands or if it boils from heat soak after shut down the expelled coolant is captured in a reservoir. When the rad cools down over night the one way valve opens and the coolant siphons back in. Rather than top up every time I check the rad it's always filled to the top and if I add anything it's more like once a year now. It's one of those things that is both simple, ingenious and totally passive.

  • Like 1

Share this post


Link to post

Hot at cruise can also be from retarded ignition timing, like a leaky vacuum advance, or lean fuel mixture from a vacuum leak such as a leaky vacuum advance or other vacuum hoses, or carb/intake manifold gaskets.  

 

Milodon and others offer a high flow thermostat that will usually solve these warm engine issues.  They start to open around 150 degrees, so the engine is slower to reach 180+.  A standard Chevy stat fits in the Datsun BTW, if you relieve the housing just a little bit where it rubs or pinches the stat.    

Share this post


Link to post

The ported vacuum isn't a leak. It's drawn from above the throttle plate and is exposed to intake vacuum as the plate moves upward above it.

Share this post


Link to post

My point was that a bad vacuum advance with a leaky diaphragm is a problem.  A common problem worth checking for.  

Share this post


Link to post

Yes, read that wrong.

Share this post


Link to post

You have to drain to change the hoses anyway so 4 bolts and lift out. I let mine sit for three days because I couldn't get back to it. What scale there was fizzed and dissolved away clean.

 

Buy Distilled water if possible or if you already have it filled use only distilled water for top ups. Over years the water boils away concentrating the dissolved minerals in it.

 

Another good idea to reduce rad top ups is a coolant recovery system. You need the special rad cap some hose and a small sealed container. I just got mine from a 720 truck. When the rad water expands or if it boils from heat soak after shut down the expelled coolant is captured in a reservoir. When the rad cools down over night the one way valve opens and the coolant siphons back in. Rather than top up every time I check the rad it's always filled to the top and if I add anything it's more like once a year now. It's one of those things that is both simple, ingenious and totally passive.

 

"Small sealed container". I use a Kirin empty beer can!  Last month I squirreled away 2 Japanese [as opposed to USA "imported" Canadian cans] on the return flight from Japan the kanji lettering was great, but I took a nap and the industrious flight crew tossed them into the recycle bin.  I guess I will have to keep using my Canadian cans until I can learn not to nap on the return Japan to USA flight!

Share this post


Link to post

By sealed I mean to keep crap out and coolant in. Doesn't need to be air tight and shouldn't be or it won't siphon properly. I have used plastic water bottles with or without a cap with hole drilled for the hose. Must be half filled and hose to the bottom. Must be large enough for the coolant expelled, usually a cup or two. Should be secured so you don't loose it or the contents.

  • Like 1

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

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