PLEASE HELP 1999 QX4 overheated

[akers912]

The other night I was driving my 1999 QX4 for about 30 minutes and when I got out I noticed steam coming from my engine. Turns out my engine was overheating. I popped the hood and noticed that water was dripping from somewhere right below my intake and was making a hissing noise. I was also smelling a lot of coolant. I couldn't figure out where it was coming from. My friend took off my radiator cap and once he did, all this dirty water came shooting out from the built up pressure. We let it cool off for about five minutes and filled my radiator back up with water. I drove another 30 minutes and my temp gauge stayed normal the whole way back. Has anyone ever had this problem or does anyone have a solution of what it could be? I'm thinking it's a loose hose or a clamp to something.

[Hawairish]

First off, hopefully there's a lesson-learned about opening the radiator cap when it's hot. Your friend should be lucky to have not had boiling-hot coolant on his hands or face. It's stamped on the cap to never do that.

As for the fluid, there's a over-flow reservoir on the driver's side in front of the radiator. It's normal for there to be some coolant in the bottle, but if it's above the Max line, then there's a problem. You'll need to check other items, but it could be due for a new cap, pump, and/or thermostat. There are ways to test them.

Keep in mind that adding water is also only a temporary solution. The radiator needs distilled/demineralized water and coolant in a 50/50 mix to reduce corrosion and maximize cooling efficiency. If you had to put a lot of (tap) water in, you should plan on doing a flush to get it back to 50/50.

Also, one thing that can temporarily help an overheating engine is to run the heater, as coolant also passes through the heater core. Doing so might be enough to get you to the next stopping point.

[akers912]

Thank you so much! How can I test all of the parts you listed?

[NismoChris]

The other night I was driving my 1999 QX4 for about 30 minutes and when I got out I noticed steam coming from my engine. Turns out my engine was overheating. I popped the hood and noticed that water was dripping from somewhere right below my intake and was making a hissing noise. I was also smelling a lot of coolant. I couldn't figure out where it was coming from. My friend took off my radiator cap and once he did, all this dirty water came shooting out from the built up pressure. We let it cool off for about five minutes and filled my radiator back up with water. I drove another 30 minutes and my temp gauge stayed normal the whole way back. Has anyone ever had this problem or does anyone have a solution of what it could be? I'm thinking it's a loose hose or a clamp to something.

First off, hopefully there's a lesson-learned about opening the radiator cap when it's hot. Your friend should be lucky to have not had boiling-hot coolant on his hands or face. It's stamped on the cap to never do that.

As for the fluid, there's a over-flow reservoir on the driver's side in front of the radiator. It's normal for there to be some coolant in the bottle, but if it's above the Max line, then there's a problem. You'll need to check other items, but it could be due for a new cap, pump, and/or thermostat. There are ways to test them.

Keep in mind that adding water is also only a temporary solution. The radiator needs distilled/demineralized water and coolant in a 50/50 mix to reduce corrosion and maximize cooling efficiency. If you had to put a lot of (tap) water in, you should plan on doing a flush to get it back to 50/50.

Also, one thing that can temporarily help an overheating engine is to run the heater, as coolant also passes through the heater core. Doing so might be enough to get you to the next stopping point.

I'm 95% sure I know what is going wrong and how to remedy it. The steam is from coolant obviously, I know, well it's steaming from pooling in or around the plenum and boiling. The air intake plenum is right on top the motor, k. This is common, common, for vg33e engines to vibrate the lower intake manifold gasket loose and cylinder number 2 will develope a coolant leak. These are metal gaskets, they don't tear, but the extra heart from that area causes this problem. NOW, the solution!!! This is a difficult job not the average DIY guy, you have to get down to the gasket between the cylinder head and the lower intake. A shop is likely to charge 300-400$ for this job, not to bad. But you can also do what I did, and it had worked for more than a year with 120° summers and extreme off road... people are going to send me to hell for this. I use bars leaks carbon fiber grade $50 bottle. I like the stuff, I'm an overland off roader and I like the added security it provides, I even bring a spare bottle for long trips. I've been using it for a year, it's temporary, I plan to fix that gasket along with other maintence all at once. I did a water pump job and added coolant to see if the leak was still a problem, it is still a problem after about 200 miles white smoke like a cloud out the tail pipe. Put in bars leaks carbon $50, back good as new, I'll red line it no problems. No leaks. ALSO!! There is a little 2" x1" house, "coolant bypass hose", cheap 5$ hose that commonly leaks in that same area. That is easy to replace, 20min or less. That little hose has been the death of some vg33e motors. 5$ hose could be a simple fix and it's less than a $50 bottle of bars leaks, and much cheaper than a 300-400$ shop charge to simply put more sealant on a damn gasket.


P.S. I think that the bars leak will remedy this small problem for the life of the vehicle, but next time you are have service done to the valve cover gasket, ask them to pretty please put some more sealant your sweet QX4 intake gasket.

[NismoChris]

Sorry, excessive heat wears the gasket sealant, not vibration. Also, my vehicle smoked White only after removing the bars leaks for a coolant flush job. Just to throw this is the mix a 17 year old vg33e needs a new fan clutch, just do it, $50 and 20min in the drive way. Reach your hand in the bay and see if the fan is difficult to move. It should be, it should resist being spun. If it easily moves with the push of a finger, time for a new one.

[Hawairish]

Thank you so much! How can I test all of the parts you listed?

The radiator cap and thermostat are generally tested with a pot of hot/boiling water and a thermometer. The specs (action temperature) of the parts are usually stamped on the part, and you basically confirm that the part is one state (i.e., open/closed) below that temp, and in the other state above that temp. The LC chapter of the FSM has instructions. But normally, if you're testing the thermostat, you've done all the work necessary to just replace it.

The water pump is the other part of the equation...if there's a belt still connected to the pulley, high probability it's spinning of course. But, that doesn't mean the turbine is worn/corroded and consequently less efficient (and potentially not pumping coolant around, causing an overheat). This usually requires removing the water pump assembly from the block and inspecting.

Chris' suggestion makes sense...check around the block for any signs of seepage. Normally, if a leak has gone unnoticed for some time, you may see light green/white chalky residue around it (or blue, or orange, depending on your coolant color). A sufficient leak can introduce air into the system, which restricts coolant flow and could burp coolant out into the reservoir...but over time, a small leak can do the same (noting that the system does attempt to purge air out during normal use).

[fueler]

Only way is to find the leak yourself. Lucky for you, coolant leaks are easy to find on this motor... there are only a couple of spots it could be coming from:

-Radiator itself (check plastic top for signs of leaking, all around the edges)
-One of a few hoses... upper radiator hose, lower radiator hose, and small rubber hose behind timing cover above water pump (cannot be seen directly but would still be obvious)... there are also hoses in rear of motor but you can skip these, based off your description
-Water pump, behind timing belt

Some leaks only show themselves during high temp / high RPM. With motor hot & running, pop hood and rev the motor by twisting the throttle with your hand... and look for leaks. Be careful & wear glasses when you do this, because hot coolant may spray... if it hits the fan then it will spray in all directions.

Whatever it is, it will happen again if you don't fix it.

Also, your buddy wasn't entirely crazy to open radiator cap.... if the radiator was low/empty, then that's the 1st step. I open it very slowly and if it starts leaking, then I immediately tighten the cap back on.

[farfrom]

IF THE LEAK IS COMING FROM THE RADIATOR ITSELF WITH COOLANT POOLING ALL AROUND THE EDGES OF THE PLASTIC TOP, WILL THE ENTIRE RADIATOR HAVE TO BE REPLACED, OR IS THERE A GASKET UNDER THE PLASTIC TOP THAT CAN BE REPLACED?

I AM EXPERIENCING THIS ON MY 1996. THE RADIATOR IS ORIGINAL AND I HAVE NEVER HAD A PROBLEM WITH IT UNTIL NOW.

[farfrom]

NOT LONG AFTER POSTING THE QUESTION I CONSULTED THE SERVICE MANUAL AND FOUND THAT THE UPPER AND LOWER TANKS AND RUBBER GASKET SEALS ON THE RADIATOR ARE INDEED REPLACEABLE.

[I SUSPECT THAT THE RUBBER SEAL (THAT SEALS THE UPPER TANK TO THE RADIATOR CORE) IS THE CULPRIT, BUT CANNOT BE 100% CERTAIN.

THERE ARE NO SIGNS OF COOLANT ON THE UPPER TANK BODY ITSELF. IT POOLS ALONG THE UPPER TANKS BASE,ALONG THE CRIMP TABS, EVENTUALLY FINDING IT'S WAY DOWN THE SIDE OF THE CORE. THE AMOUNT OF COOLANT LOST IS VERY MINIMAL.]

THE TROUBLE IS, I AM TOLD, THAT THE PARTS HAVE BEEN DISCONTINUED BY NISSAN.

A LOCAL DEALERSHIP HERE IN TOWN WILL NOT EVEN BOTHER TO REPLACE/FIX RADIATORS AND WILL ONLY DO A COMPLETE REPLACEMENT.

I WAS ALSO INFORMED THAT NISSAN OFFERS A "VALUE LINE" OF PRODUCTS THAT ARE MADE FOR NISSAN, BUT NOT BY NISSAN, AT A CONSIDERABLE SAVINGS (COMPLETE RADIATOR $200 VS OEM $700).

[Upgrayedd]

NOT LONG AFTER POSTING THE QUESTION I CONSULTED THE SERVICE MANUAL AND FOUND THAT THE UPPER AND LOWER TANKS AND RUBBER GASKET SEALS ON THE RADIATOR ARE INDEED REPLACEABLE.

[I SUSPECT THAT THE RUBBER SEAL (THAT SEALS THE UPPER TANK TO THE RADIATOR CORE) IS THE CULPRIT, BUT CANNOT BE 100% CERTAIN.

THERE ARE NO SIGNS OF COOLANT ON THE UPPER TANK BODY ITSELF. IT POOLS ALONG THE UPPER TANKS BASE,ALONG THE CRIMP TABS, EVENTUALLY FINDING IT'S WAY DOWN THE SIDE OF THE CORE. THE AMOUNT OF COOLANT LOST IS VERY MINIMAL.]

THE TROUBLE IS, I AM TOLD, THAT THE PARTS HAVE BEEN DISCONTINUED BY NISSAN.

A LOCAL DEALERSHIP HERE IN TOWN WILL NOT EVEN BOTHER TO REPLACE/FIX RADIATORS AND WILL ONLY DO A COMPLETE REPLACEMENT.

I WAS ALSO INFORMED THAT NISSAN OFFERS A "VALUE LINE" OF PRODUCTS THAT ARE MADE FOR NISSAN, BUT NOT BY NISSAN, AT A CONSIDERABLE SAVINGS (COMPLETE RADIATOR $200 VS OEM $700).

Depending on the age of the radiator it would probably be best to replace it rather than rebuild it even if rebuilding was an option. Replacing a seal won't clean out any blockage within the radiator that might have built up over time.

A Denso radiator is less than $75 on rockauto.com.

[farfrom]

INTERESTING.

SO WITHOUT ADDRESSING (THE POSSIBLE CAUSE OF THE LEAK=BLOCKAGE) REBUILD/REPLACING THE RADIATOR WOULD BE AKIN TO A BAND-AID FIX.

IS THERE A DIRECT RELATIONSHIP BETWEEN A BLOCK/BLOCKAGE AND A LEAK, AS IN...BLOCKAGE-->INCREASED PRESSURE-->INCREASED STRESS ON (WEAK PORTION OF) THE TANK SEAL/GASKET-->LEAK ?

IF SO, WHAT ARE THE (OTHER) SYMPTOMS OF POSSIBLE BLOCKAGE ?

IS THERE A TEST THAT ONE COULD USE TO CHECK TO DETECT POTENTIAL BLOCKAGE ?

WILL A COMPLETE SYSTEM FLUSH BE ABLE TO CLEAR OUT A BLOCKAGE, OR WILL THE BLOCK BE MORE LIKE HARDENED DEPOSIT BUILD-UP THAT WOULD REQUIRE A MORE SUBSTANTIAL APPROACH ?