plat

I've posted before about this but now have more information, actually out of ideas now.

Car gets hotter than normal when hot outside or going uphill. I can keep it in check running heater.

• radiator is full
• radiator looks clean inside and outside
• both hoses hot
• fans work
• air from radiator is hot
• heater works
• rad cap holds pressure
• no coolant leaks
• no coolant is consumed or lost over time
• no headgasket issues apparent

In fact, the rad cap never opens under as much as 30psi when I tested it. What affect could this have and should I get a new one?

I have also noticed that there is NEVER any pressure in the cooling system. The rad hoses are soft and squishy even when the thing is really hot.

I unfortunately cannot pressure test the cooling system because the stupid test kit doesn't fit the radiator for some reason, though it is the correct connector.

I figure water pump can't be bad or heater would not work and rad would be cold.

I figure thermostat must work or rad would be cold.

I figure radiator must work because hot air comes out of it.

No water in oil, no oil in water, and no bubbles in radiator when I start the engine. So headgasket seems good right?

What else could there possibly be wrong?

I have no codes except when coils fail and misfire.

This all started the same week as the first ignition coil failure. Three more have since failed in only a few hundred miles, including one of the brand new Hitatchi ones. Could there be any connection between the coil failures and overheating?

Next I will check the plugs and then out of ideas.

JvG

I'd say that the coils are failing due to overheating, and that you need a new radiator cap.

The radiator cap is inexpensive. Try a new one as an experement.

Also make sure that the neck of the radiator which the rubber portion of the radiator touches is smooth and free from deposits.

KP11520

Could the impellers in the water pump be reduced or failing? Just enough to not point to the water pump?

plat

I'll try that and hope it's the fix. Really the only thing wrong I can see.

Do you think only minimal heat could kill them that fast? I always turned on the heater as soon as it crept above the middle of the gauge and kept it at normal temperature that way. It never got super hot.

plat

Honestly, this has always been at the back of my mind. I've heard of this failure mode being common on other vehicles but have never read of a case on the Maxima. All I seem to get regarding water pump failures are leaks.

But it would explain how everything appears to still work normally but maybe just enough capacity loss to cause a problem under high load conditions, hot outside, etc.

Cavitation

plat

Oh also, I checked the plugs and they are the correct platinum NGKs and look great. 0.040" - 0.044" gap and no visible wear, fouling, or abnormal deposits.

So that rules out bad plugs for misfire and coli failure.

DennisMik

iTrader: (2)

I think there are 2 things going on here.

I think an important clue is that the cooling system never pressurizes. As we all know, it should. There are only 2 reasons why the system would not pressurize. 1) the engine does not heat up. 2) there is a leak that allows pressure to escape.

I don't know how the engine could run and not heat up the coolant. That and the fact the op says he uses the heater to keep the temperature down tends to rule #1 out.

A leak in the system (#2) is more likely. We normally assume that a leak means there is water dripping on the ground, but the exact location of the leak could allow pressure loss without water loss. I can only think of one spot that would do this - the radiator filler neck. A bad radiator cap is the most likely reason, but if the bottom of the metal neck where the radiator cap seals to the neck has a dent in it, another cap won't help.

You also need to find out what the coolant temperature actually is. Just because the cooling system doesn't pressurize does not guarantee that the engine will overheat. Pressurizing the cooling system serves to increase the boiling point of water. 14 pounds of pressure raises the boiling point of water to about 250ºF. Antifreeze also raises the boiling point of the water, but I don't know by how much. If the air conditioner is not being used and the cooling system does not have any problems, the coolant temperature will not go above 205ºF. If the air conditioner is on, the temperature should not go above 212ºF.

Again, monitor the coolant temperature. You can do this with an OBD code reader that has a live data capability. Plug it in and watch it while you drive around. It is possible that the engine is not overheating, that the temperature sensor that runs the gauge in the dash is bad.

M in KC

Go get another cooling system pressure tester that fits your radiator from a loan-a tool program. A non-contact heat gun like the $20 unit sold at Harbor Freight is a great diagnostic tool.

I think DennisMik has you on the right course: 1) leak 2) poor water pump performance 3) bad temperature sending unit 4) bad radiator cap.

I hate throwing parts at a problem in hopes of resolving it. That's why a cooling system pressure tester and a IR temp gun should be your weapons of choice here and a real time OBDII reader if you have one or can spring for one.

JvG

The key issue is that there is no pressure.

A bad water pump impeller would cause overheating, but the coolant pressure would rise.

A bad coolant temp sensor would indicate an incorrect reading. But the system would still be under pressure.

You are leaking pressure from somewhere.

Possible locations.
1. The radiator cap. Buy a new one. It's cheap.
2. The radiator it's self. Look for signs of moisture on the fins. You might want to remove the fans for a better look.
3. A hose somewhere. Look carefully.
4. Head gasket. This is unlikely, but possible.
a sign would be a steam cleaned spark plug.
You might see bubbles in the coolant when the rad cap is off. Remove the cap only when the coolant is still cold.

​​​​​​Do you see white exhaust clouds whIle you blip tge throttle? I hope not.

marianm

With an inefficient water pump, driving at higher rpms with less load (lower gears) would keep the temps lower. Something to try.

DBear

If the radiator is full, then you're not losing coolant, right? You say you have no pressure in the system, but you're only testing it by squeezing the hoses?

I would question that last statement. I haven't squeezed the hoses on my Max for a while, but I don't think a good hose should be soft. If your lower hose is old, it may have gotten squishy. Then when you accelerate or go uphill, the water pump increases the suction, and that can cause it to collapse (maybe only partially). I'd look into replacing the hoses.

And I think thermostats can sometimes fail partly closed. That's another fairly easy fix.

If in fact you are leaking coolant, also check the hoses under the throttle body. Sometimes you get small leaks in there.

plat

Edit: more information

I found out that the cap is actually not failing to release and is probably fine. The piece of **** test kit compresses the spring so much that it has no room to move in order to release when the cap is installed in the tester, so it is totally useless.

JvG

The pressure tester would cause the hoses to swell under pressure. Then releasing the pressure would allow the hoses to return to their normal diameter. This would explain the spewing. Normal.

plat

This is a video of it after warming up with cap off. Maybe still air in there? Bubbles continue after it's hot, is that more air or boiling coolant?

Can also see the coolant jump when I rev the engine, how does this look for flow?

All temps I see when fully warmed up are 160-180 but indirectly through the hoses.


https://www.youtube.com/watch?v=mxbR...ature=youtu.be

JvG

Sometimes members have replaced cooling system parts or drained coolant, then have problems afterwards.

They need to bleed out any remaining air in the system, or overheating can occur.

This cam be done by removing the rad cap while the engine is cold, then raising the front of the car on ramps, or parking uphill. Then they run the engine until the thermostat opens. Blip the throttle from time to time. Let the car run for perhaps 30 min.

DennisMik

iTrader: (2)

I watched the video and have these comments/suggestions. The temperature gauge showed 168º which is the opening temperature for the thermostat, so the thermostat seems to be working as it should.

Looking at the radiator filler opening, I think there may be air in the system. A bubble would come out once in a while and that is not normal. If the cooling system were purged of air, there would be nothing to create a bubble. As for the coolant surging/jumping when you rev the engine, that is normal because the water pump is running faster.

As advised by others, try bleeding the air from the system. Raise the front of the car at least 12 inches and run the engine for a few minutes after the thermostat opens. I personally raise just the left (driver) side when I do this but others seem to have equally successful results when raising the entire front.

KP11520

So, let's revisit the logic ladder........


The Coolant Reservoir.... when filled half way, does it change after driving a while?

plat

Thanks for looking at it, I'll try bleeding it out next. My thought too, the temps seem normal and see a drop from hot to cold side of radiator so it all seems good.

As far as the reservoir, if the level does change, it isn't very much and I really haven't noticed it. Should I add coolant to the reservoir and look for changes? Currently it is below half but above the lower line.


Also, some guys on another site seem insistent that the bubbles and overheating are because of a blown headgasket, despite passing a blocktest I did yesterday. How likely do you think it is for the blocktest to pass and still have headgasket leak?

JvG

The block test confirms whether or not combusion gasses are present in the coolant.

I have experienced both possibilities. One time tge block test fluid changed from blue to yellow. So indicated a blown head gasket. I found a deformed head gasket when I removed the head.
Other times tge test fluid stayed blue. I found other reasons behind the overheating issues.

One question...... do you live in an area with hard water? Do you see evidence of limestone deposits in the radiator?

plat

Cool so I can take that negative result as being absolutely certain?

The water is hard here but I think it looks good inside, what do you think?

I know it looks kind of crusty on the outside of the radiator there but that was from it overflowing while checking it and wasn't there before.

JvG

The inside of the fins look like they are not blocked.

I used to live in Salt Lake City. They have hard water, dissoved limestone. My first cars radiator looked like the inside of a cave. My car overheated frequently. I was a teenager at the time. I could not understand why at the time

KP11520

How does your motor oil look? Exhaust whiter than normal?

I'm thinking there's some sort of a compromise somewhere.

Usually through heating and cooling, the reservoir contracts and expands and if there's air in the system (with full integrity) the reservoir will go lower and displace the air in not too long a time. If that normal push/pull is not happening, IMO, it's breached.

Probably something small between the coolant and exhaust gas on one of the head gaskets or any place where they almost intersect. If it's small, the exhaust pressure will keep the coolant in the coolant side when running and some extra gases too. Start the car after sitting over night and smell the fresh exhaust quickly before any drippings burn off. But then again, it might not drip back into the exhaust side if there's an air pocket right there.

OUCH!

plat

The oil is clear amber and there is no white foam stuff under the filler or anywhere that indicates water contamination. Do you mean the color of the exhaust gas itself? It's not visible at all and definitely no white clouds or anything. I will check for any apparent water drops or condensation after starting in the tailpipe tomorrow.


That's too bad about the hard water. Isn't the rule of thumb that only distilled goes into the radiator? I'm curious if you think my radiator could be original or has been replaced recently?


Since it seems to have had a lot of air in the system and keeps releasing more despite passing blocktest, do you think it's possible that it wasn't bled correctly after the last work but the pocket was located somewhere that didn't cause a problem. Then, a few weeks ago that pocket suddenly moved and stuck someplace that is now causing a problem, overheating?

JvG

Yes. Exactly.

Please tell us more about you reference to the last work it has had. What was done , or replaced, and when. Recently?

If you have not already done so, please raise the front of the car about a foot. while the engine is cold. Remove the radiator cap. Run the car at least ten minuites. Blip the throttle once in a while.
​​​​​​
This experiment will either fix your problem, or confirm that something else is causing it.

plat

KP11520

IMO, most likely it's one of two situations.....


One, exhaust is getting into the coolant system somewhere.


Second and more likely based on your last post, there's either a blockage or the water pump isn't giving enough circulation for the hottest part of the system to come to a boil.


JvG is a wiz with real experience and hopefully can offer how to pinpoint which.

JvG

The foam could be steam from overheated water.

Especially so because it goes away when the fans come on.

If it were me, I'd suspect blocked radiator.

I'd remove the radiator and take it to a radiator shop for a flow test. T hat determines how much of the radiator might be blocked with crud. It's not leaking, but not cooling either. My first car was like that, filled with limestone.

If the radiator is old and crappy anyway, I'd replace it

Radiators do not cost all that much on Amazon or Ebay. This can be considered as preventative maintenance.

You are at the point when professional help could be considered. But that costs money. The same money could buy you a new radiator.

JvG

Id like you to try another experiment. You mentioned that both hoses are hot. Also that air from the fans is also hot.

logicly, the water pump sends hot coolant to the radiator. The inlet hose should be hot, while the outlet hose should be noticeably cooler. The air from behind the radiator should be hot.

So either the radiator is not doing its job (most likely) , or the water pump is not doing its job. (Less likely, but members have reported this.

I'd pour some food coloring in the radiator. It should get diluted very rapidly if the pump works, less rapidly if it does not.

the radiator is easy to replace, not too costly.
The water pump is not too costly either, but is a pita to replace.

KP11520

Hey J,


Do you think the radiator could be that restricting even though both (top and bottom) hoses get hot pretty quickly?
EDIT: You just posted and answered already. lol



The cheapest things to start are flushing the whole system and changing the thermostat if the radiator isn't restricting. I did my radiator like 7 or 8 years ago. So if it's never been done, I'm with JvG and it's pretty much time.



Years ago I think it was Prestone who made these: https://shop.advanceautoparts.com/p/...020%7CL3*15923


Drain the system and capture the used coolant into containers for proper disposal. Then splice in the kit and fill with water and some sort of cleaner:

https://shop.advanceautoparts.com/p/...020%7CL3*15923


Follow directions and run engine for a while. Flush the system with water totally. Drain enough water to add enough new antifreeze (straight) to make a 50/50 solution when topped off with water.


But wait if you suspect something else is causing this and address that first. Maybe the previous owner went nuts with "Stop Leak" and caused some trouble. Or put windshield washer fluid in the radiator or reservoir.



But there's something going on here that's not the usual suspect. I can't see the label next to the radiator fill cap, but it looks like it has been replaced.

JvG

KP, and others..... we have to diagnose a car which we can't see, smell, or touch..

we know that heat is traveling from the engine to the radiator, and that both hoses od the radiator are hot. So we can assume that the thermostat does operate properly. Or it would not allow water to pass. So if the thermostat was bad, and the water pump was good, we would expect no water flow.

But we do get heat flow. So the the thermostat is performing properly.

we know that the coolant in the radiator is boiling, hence the bubbles. So either the radiator is not cooling, or the pump is not flowing. The food coloring will get diluted quickly if the pump works, or slowly if it isn't.

the flow test I mentioned would confirm if the radiator is working properly. The
replacement of an iffy radiator also confirms that coolant flows through the radiator if the pump performs as it should. But that does cost money.
If there is still no proper cooling, the cause would be the pump. In which case, we wasted some money by buying a radiator which we don't need yet.. but is nice to have.

Frankly, we are spending money, buying discount parts and investing our time, based on educated guesses. While a proper mechanic would spend twice as much money on parts which he also gueses we need, and also get paid 100 bucks an hour. He probably has better guesses than we do.

id rather have new parts I don't really need yet, rather than pay 100 bucks an hour for an opinion.

I'm usually right most of the time.

My own car has a new radiator because it cracked at the fins, a new water pump because it leaked, and a complete set of hoses it didn't really need yet.

vqmaxman

What you wanna do is change The bottom and top radiator hoses. When the hoses are changed check and look for any build up in the radiator. The next step is to see if it's doing the same thing again. If the problem is still there change the water pump it might be failing and for the radiator if they were no debris when you replaced the hoses and did a full cleaning flush on the radiator. It's still acting up change the radiator.

JvG

Possibly. A collapsed hose could cause those symptoms.

klobbersaurus

easy way to check is get an infrared thermometer, those are cheap and you can check the actual temps across the radiator, then u can tell its clogged in that spot if the temperature drops from the rest of the radiator

DennisMik

iTrader: (2)

Watch the video posted by the op back in post #14. He is using an infra red thermometer.

DennisMik

iTrader: (2)

I have never seen a radiator do white foam like the photo the op posted in a post # 25. The coolant evidently has something in it, but I don't know what it might be.

As a similar point, the photo in post # 20 shows what looks like a weak solution of antifreeze. Maybe flushing the cooling system might help.

KP11520

I definitely agree with Dennis on this as stated at the end of my last post! Windshield washer fluid in the reservoir perhaps? Some people are CLUELESS when under the hood trying to make the dashboard lights go out.


And I totally agree on a real and complete flush and antifreeze replacement to 50/50. And check ALL hoses and just go for it and replace them all.


Rock on Gentlemen! You all are good peeps and always help!

plat

I'll have to strategize testing these so it's not hot from the food color test when I drain it and take the hoses off. Maybe have to do one test today and one tomorrow.


Actually I have run the IR thermometer over the radiator at different points with the car is warmed up and it only reads like 115* close to where the top hose comes in and that is 170*. I think because the individual fins are so small and air is passing over them that they are much cooler than the inside and so not really useful to measure.


All I can go from the fact that there is only a 10* drop from hot to cold hoses on the radiator which at first thought doesn't seem like enough.


I can't thank you guys enough for putting your thought and experience into this.

KP11520

You know, you could buy one of those flush kits I previously posted and the chemical cleaner in the same post and flush the entire system and just fill it with water and see if the problem just goes away (like something is in the coolant that makes it suds up when hot and cavitated by the water pump)



Then if it goes away, you know it was in the coolant and making you crazy thinking it was a mechanical problem. It happens. You need a flush/replace either way! All you have to loose is water.


Then replace the hoses and flush again and 50/50 the mix.



DONE!

JvG

I agree with what kp said, and also with another members suggestion regarding replacing the two radiator hoses.

The top radiator hose is generally the first one to fail.

CS_AR

Is there a crack in the radiator tank just above the last "c" in word calsoniC?