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Cooling sytem problem

6918 Views 33 Replies 11 Participants Last post by  BoostinIX
I've been trying to figure out my cooling problem for weeks now, now I'm just frustrated.
First the car was running quite hot(2nd to last hash mark) ONLY when the A/C was on, and mostly in stop and go traffic, so I figured air in the system, so I bled it according to a few different threads, to no avail...
The car did cool down a bit(single hash, and rarely back down to normal temp) when I started to drive and not just idling, but would climb if I'm in stop and go or idling too long.
So I decided my thermostat may be bad, so I took it out and noticed lots of rust on the thermo and gunk around the water neck. The factory thermo's internal rubber gasket looked like crap, but (i tested it in boiling water) and it did still open around 80C, and testing my new one, it also opened up just fine..
So I install my new thermo and also put on new upper and lower hoses just to be sure.
Now my car runs way hotter, i'm sure it would overheat if I let it run longer. What is interesting is the lower hose is cold, while the upper hose it super hot, which tells me the thermo isn't opening:WTF:
Unless my new thermo crapped out from the time I tested it until the time I put it in which was like 30mins, i'm narrowing it down to a few possibilities.

1. I didn't bleed the system properly and the trapped air has made it to the thermo, causing it to stay closed.
2. My radiator is plugged, which could've been my problem the entire time since my stock thermo seemed to work okay after testing it. However, my water pump should be okay since no coolant is leaking from weep hole, and the previous owner said he replaced it a couple years back.
3. I don't know if this matters, but whenever I bleed, I turn the car on and heater to full blast, but hot air doesn't seem to come out of the vents, or if it does, it takes a LONG time before warm air even starts to come out.:scratch:

So my questions would be:
Can a plugged heater core cause overheating or exacerbate a trapped air problem?
So far i've read multiple ways to bleed the engine, with bleed screw open and rad cap open, rad cap closed, revving engine to make air escape... What is really the best way to bleed the system?
Finally would trapped air really force the thermostat to stay closed, and if so, how can I get that trapped air out now?
Sorry for making this post so long but I wanted to state all my symptoms so you all could give me a good diagnosis. Thanks again for any help! This problem is killing me.
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Ok I've had this problem,ill tell you what I did but you should check this along the way. Check to see if the belt is snug on the pully and that it turns it. Check your water neck ,passages,and water pump for rust build up causing a clog. What I did was replace all coolant components. I pulled every thing and flushed the block,then I replaced waterpump ,belts,theromostat , and radiator. Also, make sure you have the right psi cap on the radiatorand that you are using the right coolant for your system. But I think your problem is radiator. Might as well do what I did and bring things up to date. Hope this help any. Cause I had that exact same problem :)
Typed via my android phone lol
Bleed the system, with the rad cap open, so you can monitor the coolant level and keep it topped off. Personally, I like to keep the car running, open the bleed plug, and let coolant run through there until there is no air/I feel that it is well bled.
I replaced the radiator cap, replaced all belts a few days ago and made sure they're tight. The fan clutch looks to be okay, as it doesn't spin freely when the car is off.
I'm going to try draining all the coolant and doing a full flush, and might as well replace the water pump while i'm at it, and if the radiator is clogged that's going bye bye too.
I'm still wondering why the heater takes so long to get hot, and now that the thermo is sticking shut, i'm thinking the heater core is plugged with rust or build up.
I had the same problem and did what you did. Ended up being my rad. But also eplaced a faulty thermostat while i was there
Ahhhhhhhh.... ^yeah I think it's definitely my radiator. Here's what I ended up doing today after a painstaking 9 hours of work:
Tried bleeding again, didn't work.
Saw a good old friend under the car.. LEAKING COOLANT!! From guess where? Another damn freeze plug!! I just replaced my passenger plug a week or so ago, today it was the driver's side plug that was leaking. After hours of pounding in a small tight place under the car, killing my back, I replaced it.
Bled again, still overheats!!! WTF! And my thermo still feels like it's not opening(cold lower hose, hot upper hose)!!
So then I said screw it, took out the new thermo(which still works after testing it in some boiling water) and replaced the water pump, which was real corroded and rusty, which also tells me the cooling system was mistreated by the previous owner.
Bled it again, and now it runs okay, but still gets a little hot when I idle too long.
Under freeway driving with a/c on it rides at a little above halfway 1/2 hash or so(which i'm sure is not normal)
Under street driving, it gets up to 1- 1 1/2 hashes above normal...
Oh, and now my heater does blow hot air, so the coolant is flowing, and the heater core isn't plugged.
Now knowing that my pump is new, my lower and upper hoses are new, the car doesn't leak coolant from freeze plugs, and my thermo is not installed, i'm left to believe the radiator is inefficient and not cooling the system enough.
Hopefully it will hold up for a few days until I can get a new radiator (any suggestions anyone?) and put my thermostat back in.
Thanks again for all the help everyone, and i'll keep you posted on the new radiator install!
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Okay so got to installing my new radiator today, and also put in a new OE nissan thermostat.
SOB still gets hot. Only climbs to very hot when on the freeway with the A/C on. I don't wanna risk overheating so I switch the A/C off just before it gets out of the "normal" range.
I just don't get it. I've replaced everything to do with the cooling system, radiator, thermo, water pump, hoses, the car doesn't leak fluid.. So???
I'm going to let the car cool down on the jackstands. Maybe I've got some kind of massive air pocket in the engine, or worse I've got a blocked cooling passage.
Okay bled again for about 20-30 mins by leaving radiator cap off, car on the ramps, squeezing the hoses, keeping heater on full blast, and topping off with coolant.
The car still wants to overheat!! Note that it only wants to overheat when the a/c is on, with it off it will run slightly above normal, but will not overheat.
WTF? I suppose i'm gonna have to bleed for an hour just to make sure the thermostat opens. I've never had this much trouble with a car overheating and bleeding.
If this doesn't work, i'm taking it to a pro mechanic I know in town, but this is really killing me. Any other suggestions? I really don't wanna spend money on a mechanic if it's something i'm just overlooking.
ive kind of had the same problem too man, have you been unscrewing the bleeder screw? and having it at a slight incline helps (front end higher than rear) and make sure your heater is on full blast when u do it, just read the fsm on it, it may help
huh sounds just like mine was doing.. i did everything i could to fix it and with no positive effects... it also could be that your block is clogged or a really rare cause a bubble of air at the top of your water pump.. I have a friend that has that problem on a ka-t to make a long story short the block went to the machine shop and clean we reinstalled everything and no more over heating =)
Yup, i've tried several different ways to bleed the car, the main constant being the car is always on the ramps and I try to keep system topped off:
1. Take cap and bleeder screw off, fill with fluid til it comes out of bleeder screw, leave screw off, rad cap goes back on. Start car put heater on full blast, and squeeze both hoses til no bubbles, then tightened bleeder bolt.
2. Leave cap and screw off, fill with fluid, leave cap off AND bleed screw off. Start car, heater on full blast, squeeze hoses til no bubbles, tighten bleed screw and put cap back on.
--these methods i tried when I was doing various things like replacing thermo, water pump and hoses. I believe I let the car idle for about 15 mins each time.
3. Leave rad cap and bleed screw off, fill til fluid comes out bleed screw, then close screw, but leave cap off. Start engine, turn heater on to full blast run til it warms and continue to squeeze upper and lower hose. Put cap back on when I feel it's bled and absolutely no bubbles come out when squeezing hoses --this time I let the car idle for about 20 mins to make sure the thermo opened(which I noted by the lower hose heating up). This method seemed more successful as it didn't heat up so rapidly after I started to drive with the A/C on, and it even cooled down after I stopped at the gas station for some cigs lol. However, after about 10 more minutes of driving the temperature started to climbed, and reached second to last hash(when I started to drive on the freeway), when I turned the A/C off and heater on, the temperature started to go down. After turning the heater off and continued to drive on surface streets, the temp stayed at slightly above half.

So could it be that my A/C fan is just shot?? I do see it turning on when I turn the A/C on but maybe it's just not turning fast enough to cool the engine with the A/C on.
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Hmm. I think at this point with all this bleeding, the car should be clear of air, but sly you may be right about the block being clogged. I'm gonna try bleeding one more time tonight, but I'm also starting to think the A/C fan is shot. I just read online somewhere that a poor running fan can cause overheating problems with A/C only. I hear we can use Ford Taurus fans on our cars. Might try that, but I'm gonna call the mechanic in the morning and ask about a high pressure flush to see if he can get any gunk, rust, and buildup out of the engine block.
Final diagnosis: either fan clutch is crapping out after certain amount of time or after certain temperature is reached, or electric A/C fan is intermittently failing.
First I took the car out for about 20 mins and didn't use the A/C at all, never got above halfway. Got home, turned the car off and turned it back on. I sat in the driveway and turned on the A/C, idling for like 20mins, it actually stayed very cool. Drove around the block a few times with A/C still on, and the temperature started to slowly climb. Got home, the temp was at about the 2nd to last hash, let it sit, and the car actually started to get cool, and the A/C was still on...
Gonna drive the next few days without A/C in hotter times of the day, and see if it gets hot. If it doesn't then I'm assuming either the A/C fan or clutch fan is intermittently failing.

Instead of starting a whole new thread I thought I'd just update this one.
Once again, summer is here and my car is running hot to the point of nearly overheating. Though I can't say I've actually overheated because I've never let it get that hot, and the coolant is not boiling in the overflow tank when car is running hot (nearly outside the "normal operating range" on the factory gauge)

To recap what I've replaced and installed over the last year:
Water pump
Nissan OEM thermostat
Upper and lower hoses
Found a bad clamp and replaced several clamps
Leaky freeze plugs(put in rubber ones to hold until I get my SR, and yes they are holding)
Cardboard upper cooling panel lol
Altima dual fans and DFI controller, no more clutch fan

Now the symptoms:
I've pressure tested the system, and it will hold 21.5 psi for 30 mins, but at 23psi(testing pressure) it will slowly leak down to 21.5 and hold.
Car doesn't visibly leak coolant, although it does leak oil from somewhere, and now seems to heat up somewhat slower than last summer. I can drive around for about 20 mins before the factory temperature gauge starts to rise above the halfway mark, and it will get up to the top of the "normal operating range" of the gauge if I drive for extended periods. Of course, the entire time I'm using A/C except when I think the engine will overheat. As a side note, ambient temperatures here in Vegas are around 100*-110*F.
Fans are coming on and even go into "cooldown" mode when running hot.
I also installed an electric Sunpro water temperature gauge and upper radiator hose adaptor to monitor water temps coming out of the engine. I don't know if this is good but as I was driving around tonight the Sunpro gauge was reading 190-200*F and the factory gauge was sitting just under the halfway point, ambient temperature was ~95*F, and I wasn't using A/C, that seems high or an incorrect temperature reading.
Sorry to make that a long read but again wanted to bring everyone up to speed with what I've done to remedy this problem, so to ask my 2 questions now:

1. 190-200*F seems to be a high operating temperature, especially since I wasn't using A/C. Is the Sunpro gauge off, or possibly my grounds are bad? I grounded the gauge inside the car and even grounded the hose adaptor. On both grounds, I sanded down to bare metal to ensure good connection. The gauge has a mechanical face and the sender is electric, if that helps.

2. Why is my car still running hot? Again, I never let the car actually overheat, and if I turn the A/C off the engine temperature actually does start to go down. Yes the factory gauge has been acting funny(as I've read these gauges do), hence why I got the Sunpro, but It does seem correct as it's not completely erratic, just somewhat bouncy when hard braking or cornering.
I've bled the car many times, taking about 15mins each time to "ensure" a proper bleed, yet the car still runs hot.

I'm going to monitor the temps on my Sunpro gauge and compare to the factory gauge over the next day or two and update what temps the Sunpro gauge is reading, though again, the Sunpro gauge seems to be reading a bit high at 190*F running temperature...

Any help with these questions would be great and hopefully will buy me some time until I can get my SR :) Thanks again folks! You are always helpful.
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Did you replace the temp sending unit? Had a ranger for a while that looked like it ran hotter when the sun was up than it did at night (only owned it from July to August a few years ago) Replaced the t-stat, temp sending unit and switched to an aftermarket guage...worked fine after that.
Did you replace the temp sending unit? Had a ranger for a while that looked like it ran hotter when the sun was up than it did at night (only owned it from July to August a few years ago) Replaced the t-stat, temp sending unit and switched to an aftermarket guage...worked fine after that.
The factory units? I haven't touched either the ECU or the gauge face, I may try the factory gauge sending unit to see if it's really just over reporting temperatures, but would rather rely on the Sunpro gauge.
BTW, the Sunpro gauge is brand new, so I would imagine it's sending unit is okay.
The factory units? I haven't touched either the ECU or the gauge face, I may try the factory gauge sending unit to see if it's really just over reporting temperatures, but would rather rely on the Sunpro gauge.
BTW, the Sunpro gauge is brand new, so I would imagine it's sending unit is okay.
I mean the thing that tells the guage what temp it is...
I mean the thing that tells the guage what temp it is...
Haven't touched it yet. Many people say the factory sending unit for the gauge face sucks and tends to be erratic/bouncy. I'm going to keep a closer eye on the Sunpro unit but I'll source a place for a new sender since I can (and have to) use that sensor in the SR :) Thanks.

As another note, I'm waiting for my breather tank to arrive in the mail. If these engines are really that difficult to bleed, maybe this breather tank will make it easier and solve my problem, if it really is air pockets.
These are temp sending units
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