521 Over heating problems

[Matt H]

My 521 starting overheating a couple of days ago. Out of nowhere I looked down and noticed the the temp gage was nearly in the red. I quickly pulled over and later managed to drive it home slowly with out it creeping up to high. I also noticed when starting it up for the second time it instantly heats up very quickly. I was wondering if anyone had any thoughts of what its likely to be and if there was anything preliminary checks I can do. Is it likely the radiator needs flushing and is that something relatively easy for a newbie? I'm trying to avoid taking it to the shop as i've had a few repairs recently which are starting to add up 😂

[Crashtd420]

Well you should be able to look into the radiator and see the condition....

 

A good flush can never hurt.... 

Best to remove radiator and back flush the block while your at it....

 

I'd probably also pull the water pump and have a look at that....

 

Beyond that might be head gasket ....

[thisismatt]

Make sure thermostat is opening...

[datzenmike]

In sudden over heating situations I turn the heater on high. It's an extra little radiator and can make the difference.

 

 

A clogged radiator or cooling system isn't sudden but does so over time. The temperature would slowly read higher over months. Sudden over heating can be a few things.

 

1/ When cooled down take the radiator cap off. Does the rad now need topping up? Is it using an unexplained amount of coolant? Can you run the over flow hose into a plastic water bottle and say if it's actually over flowing??? Start the engine with the cap off and let warm up. Does the level rise and over flow? Are there bubbles? When warmed up is it steamy, does the exhaust smell like anti freeze?? This could be a blown head gasket. Compression gets into the cooling system and pressurizes it above the 13 PSI rating of the radiator cap and it blows coolant out the over flow. Lower coolant level is what causes the over heating.

 

2/ The thermostat may have failed. These things are mechanical and don't last forever. I find testing them too much bloody work to find a/ there's nothing wrong with it, all that for nothing.... or b/ it's bad. As you have it apart anyway why not simply replace it? If it fixes the problem then that was it, if not, you have many good years of operation ahead of you with a new one. Expect to spend about $8 on a good quality one, don't get the $1.99 WallMart crap.

[Matt H]

Ok this didn’t go entirely to plan and I may of just learnt a valuable lesson. I started the car up with the rad cap off and squeezed the out flow pipe to the thermostat a few times to try and manually burp out some of the air. I left the car running for 5 mins to see if the coolant would start bubbly which it did ever so slightly. 
 

however, when I noticed the engine was still overheating and the level in the radiator started to rise close to the top I cut the engine and it literally exploded out the top of the rad and all over my new alternator which smoked a little and made a weird noise.

 

I’m a little concerned I just smoked a brand new alternator as I literally just had it replaced last week. A lot of coolant flooded out the top of the radiator and onto the alternator.

 

Is there anything I can do before trying to restart it or should I not restart it at all until all the coolant has evaporated?

 

[datzenmike]

Coolant shouldn't hurt an alternator. It will spin and clear itself out.

 

Overflowing could be a bad thermostat that isn't opening. When the water in the block boils it will push coolant out in a hurry!!!!. I would change the thermostat for $8-$9 and eliminate it as the cause.   

[Matt H]

Yeah it definitely caught me by surprise! Let me replace the thermostat and get back with an update. Appreciate your help thanks mike!  
 

 

[Stoffregen Motorsports]

Two things -

 

Never assume your gauge is accurate. Get another gauge, preferably a mechanical gauge or even a meat thermometer to verify the actual coolant temp. The meat thermometer (should read up to at least 230F) can be put inside the radiator filler neck while the engine is running (but not driving) to check the temp.

 

Second, to burp the system, the easiest way is to park with the nose of the vehicle pointed slightly up (jackstands can work too) and run the engine with the radiator cap off until the thermostat cycles a couple of times. Then shut the truck off and let it cool before putting the cap back on the radiator. You may need to top it off a little as it cools. Once the cap is on, and the engine comes up to temp again, there may be a little coolant escaping from the overflow tube, and this is normal. It will do this until the coolant level equalizes. How can you tell when the thermostat is cycling? Easy, you look down the filler and will see coolant moving. If you have an infrared heat gun, you can also check the temps across the radiator, top to bottom, side to side. An engine that's up to temp will have a radiator that's pretty evenly heated.

 

Rinse the old coolant out of the engine bay and off the engine or it will stink and always smell like it's overheating.

 

[Stoffregen Motorsports]

Let me clarify, to your earlier comment about coolant spewing out of the radiator. That doesn't necessarily mean the engine is overheating. If the coolant level is low because of an air pocket in the system, when that coolant hits the hot engine, it will blow back like that. So yeah, if it spilled over, it might just be because there is air in the system.

[MikeRL411]

2 hours ago, Stoffregen Motorsports said:

Two things -

 

Never assume your gauge is accurate. Get another gauge, preferably a mechanical gauge or even a meat thermometer to verify the actual coolant temp. The meat thermometer (should read up to at least 230F) can be put inside the radiator filler neck while the engine is running (but not driving) to check the temp.

 

Second, to burp the system, the easiest way is to park with the nose of the vehicle pointed slightly up (jackstands can work too) and run the engine with the radiator cap off until the thermostat cycles a couple of times. Then shut the truck off and let it cool before putting the cap back on the radiator. You may need to top it off a little as it cools. Once the cap is on, and the engine comes up to temp again, there may be a little coolant escaping from the overflow tube, and this is normal. It will do this until the coolant level equalizes. How can you tell when the thermostat is cycling? Easy, you look down the filler and will see coolant moving. If you have an infrared heat gun, you can also check the temps across the radiator, top to bottom, side to side. An engine that's up to temp will have a radiator that's pretty evenly heated.

 

Rinse the old coolant out of the engine bay and off the engine or it will stink and always smell like it's overheating.

 

 

Or install a "TEE" fitting sold as part of a Prestone flush kit in the high point of the cooling system.  This is usually in the heater hose line.  Loosen the capped cover in the plastic fitting and the system will burp itself as you fill it,

[Stoffregen Motorsports]

Those help, but unless it's the highest point in the system, it won't let all the air out.

 

Heater valves should be in the HOT position when bleeding a cooling system to help the heater core fill up.

[datzenmike]

The top of the thermostat is the highest point on an L series engine even with car sitting level. Have a good look the heater core is much lower. If you have an earlier L16 the thermostat has a jiggle valve and that vents any trapped air. All others let the air out (if any) as soon as the thermostat opens and radiator level must be checked and topped up. Trapped air? never seen this.

 

I have seen water gush out of a cold engine when the cap was removed but that had a blown head gasket. The cylinder acted like an air compressor pressurizing the cooling system. As soon as the cap was released water was pushed back through the bottom rad hose an up and out.

[Stoffregen Motorsports]

3 hours ago, datzenmike said:

Trapped air? never seen this.

If the heater valve was turned to the cool position when the cooling system was filled, this could cause trapped air.

 

Even jiggle valves don't work so quickly, so the first cycling of the thermostat almost always releases an air bubble.

Edited September 7, 2022 by Stoffregen Motorsports

[banzai510(hainz)]

Radiators dont plug up in a instant.

 

Make sure the inlet hose down by the radiator is not soft and collapses when the motor is reved up

 

I have went tp a Pop Lever Radiator cap .

 

heater position is a minor issue I alwaya leave mine ON so to keep the wear to a minimun on the valve.

 

 

I would do a radiator stat swap and DRILL  a 1/8 where the giggle valve was

 

Hope these 2 things fix it.

 

you could always run it in the morning on a cool day with no stat and see if it over heats / pressurizes then you kow you got a head gasket

 

shit maybe the timing is off, but its a simple ez look to see where timing is at. Hail Marry guess.

 

make sure your oil is OK. I had a front cover pin hole when hot all the water leaked into the oil pan from back of the water pump.

 

this is a old 521 yull alwasy have to work on it its 50years old. If you wanted a better truck a 90s toyota wit a might be better with a 22R. but they not as cool as a 521.  I have to work on my all the time. Most part store stuff is chines and dont last. Altanators ect......

Edited September 8, 2022 by banzai510(hainz)

[datzenmike]

Early L16s had the 'jiggle' valve in the thermostats because they didn't have a by pass plumbed into the intake coolant return line. The jiggle valve, or the bypass, pushes the stagnant water around the thermostat away, replacing it with warmed water from the head so that it opens more closely to the actual temperature of the engine. The jiggle valve isn't a good as it displaces cold water in the rad back into the engine slowing the warm up. The by pass is a closed circuit that returns the warming water directly back into the water pump at the lower radiator hose inlet.  

[Matt H]

Thanks everyone. So I switched out the stat and tried my best to bleed out the air from the radiator ensuring the heater core was on. The heater core in my truck is switched on permanently as I do not have a switch attached so I turned the fan up to full (Felt a bit weak in my opinion). Ignore the coolant in the bottle as that was already there (I get the sense it was not over flowing into the bottle when warmed up either) 

Unfortunately the car is still overheating. I let in run for for around 5 mins and the temp gage started to rise again. I noticed afterwards the radiator started to smoke ever so slightly. Not sure if it was excess coolant or just the fact it was very hot. The top of the radiator was like red hot and the bottom luke warm if that.

I havent flushed the radiator yet and maybe thats my best next step. I curious knowing that i've replaced the thermostat does it sound like perhaps this might be an issue with the water pump?

There was also some residue in the stat housing that I presume to be rust...

 

 

 

[Thomas Perkins]

So funny.Never seen a battery bigger than the engine.I just got mine straighten out and I replaced everything,including the bad alternator.My  temp.sender and sensor were,good,so was the thermostat.One of the dowels keeping the water pump straight came out 2 water pumps ago,causing it to scrap on the inside.I bought 6 from Nissan and put another water pump in.Found out the temperature gauge was bad.It wasn't running hot.So you never know till you replace everything.With that corrosion,I would say water pump and radiator.

 

Edited October 8, 2022 by Thomas Perkins

[banzai510(hainz)]

On 10/8/2022 at 1:39 PM, Matt H said:

I curious knowing that i've replaced the thermostat does it sound like perhaps this might be an issue with the water pump?

you could remove the water pump and if you see water flowing to the top of the radiator then the pump works. I would try to find a WPN032 Aisin pump made in japan if you do get one. its the cast impeller.

remember most time the stat is closed and open let the hot out then cool from the bottom.

 

heres a good one to get as a spare anyways. I cant find the aisin one unless you go to zcardepot the Japan unit 50$

https://www.ebay.com/itm/372989962803?hash=item56d7ef2a33:g:wOoAAOSw8gBeb9TD&amdata=enc%3AAQAHAAAAoCyvL63jKuIwyAnqA1dZe1Shsd7e8lufzDjPBfbyd8wOSBlUL%2FXgk9%2F4j5b8yRB%2Bei73q0MP92rp49iqKuTh9TQ%2FfLlMvnUkwXGiK7L1%2BmI0L%2Fwrh%2FHC8SLsoKOYKhG5TjDD17VlNFninl30SAFElrkp%2Ba74FFLcQs094LEw%2BRX5I5sPeUj6a9I7Slp1cmhRG%2Fjhv8kglxq105tbG9SRiaE%3D|tkp%3ABk9SR_jQvLb4YA

 

al my water pumps went bad by leaky seal or just fell aprt worn out but hitting the front cover inside.

Edited October 10, 2022 by banzai510(hainz)

[MikeRL411]

19 hours ago, banzai510(hainz) said:

you could remove the water pump and if you see water flowing to the top of the radiator then the pump works. I would try to find a WPN032 Aisin pump made in japan if you do get one. its the cast impeller.

remember most time the stat is closed and open let the hot out then cool from the bottom.

 

heres a good one to get as a spare anyways. I cant find the aisin one unless you go to zcardepot the Japan unit 50$

 

al my water pumps went bad by leaky seal or just fell aprt worn out but hitting the front cover inside.

 

Chack with your local Nissan dealer.  Nissan used to sell water pump seal replacement kits.

[Duncan]

I might have missed it if was suggested, but I have had a few radiators clog up.  I feel around the front of them to see if there are any cold/cool spots when it is up to temp.  It's happened to me a few times, and any decent radiator shop can fix it rather easily.  I sometimes forget, but checking the simple things first is generally a good way to troubleshoot.

 

As always, my advice is worth exactly what you paid for it.

 

 

[datzenmike]

Has it actually boiled over?????? Maybe gauge or sender is wrong. Shoot the thermostat housing with an IR infra red 'gun' and see. Maybe nothing is wrong. Find out if you have a problem before swapping expen$ive parts that don't solve a problem that may not exist.

[banzai510(hainz)]

any update?

this only takes 20 mins to pull the rad and put a hose to it and see if water flows throw it.

Maybe same rad cleaner ect..

then while out put a new pump on there but I dont think the pump vanes like dissapear!!!!!

[Stoffregen Motorsports]

20 hours ago, datzenmike said:

Has it actually boiled over?????? Maybe gauge or sender is wrong. Shoot the thermostat housing with an IR infra red 'gun' and see. Maybe nothing is wrong. Find out if you have a problem before swapping expen$ive parts that don't solve a problem that may not exist.

That's the scientific way. Verify that there is an actual problem before proceeding.

[datzenmike]

Wouldn't be the first time 3 or 4 pages of suggestions were posted only to find out the OP's perception of over heating or overcharging wasn't and everything was normal. What's that ticking sound when making a turn? Oh that's just the flasher unit.

[Stoffregen Motorsports]

I used to be a chef for a living, and when I had interns, they would invariably come to me with questions. Questions like - is this burnt? I would reply, if it smells burnt, or tastes burnt or if you saw fucking flames, then yes, it's probably burnt.

 

Trust your senses.