Overheating, How many CTS?

bob89sentra · Nov 1st, 2005, 08:00 AM

Hey guys does anyone know how many CTS an 89 sentra GA16i have? I know of the one for the radiator fan on the thermostat housing, and the one on the intake manifold above the water pump, which I assume is for the gauge in the dash. Is there a third one for the computer, or does it use the same one for the computer as for the gauge? I replaced the one in the intake manifold about a year ago, and still no matter what, It could be -10 Deg out side, and my gauge says I'm overheating (3/4 temp). The only way to cool it down, is to down shift so my RPMs are at 4,000 or above. I replaced the radiator, heater core, thermostat, water pump, both CTS that I know of, and did a radiator compression test, and no leaks. I've flushed the radiator many times, and it did not help. I took a new thermostat and drilled a hole .250", and the thing would not ever hit even 1/4 temp even in the summer. I also looked into the voltage regulator on the dash, and it did not seem to make any difference. I just rebuilt my entire engine about a month ago.... Had the crank turned, block bored, rebuilt a head from the wrecker, main and rod bearings, new water pump, oil pump, timing chain, tensioner, guides ect ect ect. I also did the swap from the automatic to a five speed stick. I love this car, and don't want to loose it. Any ideas on what to check next? This will not beat me I will win. Thanks for any info in advance. Bob

dreamteam · Nov 2nd, 2005, 01:26 AM

Hey Bob, you gotta' be luvin' this........
There isn't much in the books about the temp sensor, so the only way to check it would be to try another one and see if that makes a difference.

However, I don't think that is your problem.

You sort of answered your own question when you drilled out the thermostat.
It appears you have an obstruction in your cooling system.

First, are you bleeding the system properly?

Second, Is your thermostat installed correctly?
And, are you using a factory stat? How about the gasket?

Third, you may have a hose that collapses only when it gets hot.
Let us know........

bob89sentra · Nov 2nd, 2005, 07:55 AM

Yes, I am bleeding the cooling system, so I'm shure there are no air bubbles. As for the thermostat I have tried about four different brands I think that they were all 195 deg. Each and every one I have tested before and after I use it, in a pot of water on the stove, and they all work fine. I have thought about an obstruction in my system, and only have a few things left to look at. The block and head have been boiled, and are very clean. Like I mentioned earlyer I replaced many parts including timing chain cover, water pump, and both sides of the thermostat housing, heater core, radiator, and about half the hoses from the waterpump housing to the intake and such. The only thing in the cooling system I have not messed with, is the intake manifold, and that steel line that crosses the back of the engine to the lower radiator hose. Does this engine have a thermostat bipass line that lets coolant circulate when the thermostat is closed? I know there are many passages inside the intake, but I can't find any documentation to show where they go. Could the EGR have anything to do with this? I have also had alot of problems with pinging, and played with the EGR. At idle it vibrates slightly, causing it to idle rough some times. I replaced the EGR vaulve, and the diaphram that hooks in front of it, and there was no difference. Is that electronic controller vaulve that the EGR vacuum lines run to controlled by the ECU? Ok enough questions for now thanks again. Bob

dreamteam · Nov 2nd, 2005, 01:30 PM

You definetely need a book.(repair manual)
Hopefully you have one.

That said, let's get on with it.

You have tried a lot of thermostats, you will need to get the Nissan factory replacement.
It is the only one with the correct bleeder vavle in it.
Also , it is rated at 180 degrees.
This bleeder valve needs to sit on the top side when installed.
nothing should obstruct it. Like the gasket or gasket material.
When it is functioning properly, it lets a small amount of coolant flow past the thermostat, thereby keeping the air out and a safety valve in.

The correct way to bleed the system is as follows:

Open the air bleed valve in the head, located under the wire loom for the spark plugs, it is a 10 mm bolt.

With the correct thermostat installed, open the radiator and pour in coolant slowly until it comes out the bleeder bolt.

You may help this procees along by slowly hand pumping the lower radiator hose.

If coolant does not come out the bleeder bolt , you either have the wrong bolt or the system is blocked.

With the coolant now flowing from the bolt, close the bolt snugly.
Replace the radiator cap and fill the reservoir.
Check reservoir level in two days.

Two more issues from your post:

Have you replaced the timing chain?

The EGR is hooked to the BPT and they are both vacuum operated.

On a side note, check the vacuum line right under the air cleaner that goes directly into the intake. This one fails a lot.

Keep at it Bob, you"ll get 'er.

bob89sentra · Nov 2nd, 2005, 07:04 PM

Well, I just got home, and looked at my thermostats, and they are 180, and not 195. As for the timing chain, I have replaced it four times in the last 6 years. I had many problems with the tensioners, but now I have a new chain, guides, tensioner, oil pump, and so on. I do have a chiltons and a haynes manual, and they are pretty vauge on many things, but they do work. I will check the vacuume line that connects to the Intake, as well as the others. The only thing I have not done on your list was to Install the thermostat with the bleeder hole at the top. I did not know that it mattered which way was up on the thermostat. As for bleeding the system, I have allwayse poured coolant in untill it was full, then unscrewed the bleeder screw, and waited till coolant pours out. When there is no bubbles, just coolant, I put the plug back in, before the level gets too low, then top it off again. I did replace the cluster voltage regulator, but I still have a doubt. I also will take a autometer temp gauge, that I bought for my Small block chevy, and see if my gauge is really acurate. I'm Hoping that I am not trying to fix a fantom. If this don't fix my problems, I will try another Intake manifold, from the bone yard. Bob

astreamk1 · Nov 2nd, 2005, 08:22 PM

2 quick questions for you. 1) have you checked/replaced your radiator cap ? I didn't see that on your list. and 2) is the cooling fan functioning ? you said you were suspect of the sending units but never mentioned if the fan was responding to the temperature level.adding/checking the temperature with a second guage may be a good idea.

My 90 started heating up on me one day and after some painful troubleshooting, I found a corroded wire on the relay for the cooling fan over by the battery.

bob89sentra · Nov 3rd, 2005, 10:44 AM

Yes It is a new radiator cap, and I have tested it with the pressure tester, and it is good to 14 Psi. As for the radiator fan it does kik in, but not alwayse at the same temp on my gauge. I have turned the AC on, to make both the fans run all the time, and the temp sometimes will go down, and sometimes not. Theese are two more reasons that I still suspect the temp gauge. I serched through my chiltons manual, (it's a 1982-1996 sentra/pulsar manual), and filtered through all the irrelavent garb, and found that for the california models there is a temp sensor for the EGR. I will check this also, to verify that the EGR is not the culprit. It also appears that there is only two coolant temp sensors, one for the fan, and one for the ECU, and Gauge. I will check the voltage at the ECU according to the book. I am not driving the car now, because I dynomited my 5speed trans

, lost all but 2nd, and 4th. I just bought another 4 speed from the bone yard, and will put it in this weekend. I love to hate this car!!

dreamteam · Nov 4th, 2005, 12:39 AM

Hey Bob, at least you have kept your sense of humor........

I think you will like the 4 speed better anyway.
They take a lot more abuse and never pop out.

PS (whispering)...I still think you have air in the coolant.

bob89sentra · Nov 4th, 2005, 06:44 AM

What do you think about me putting another resivour at a higher level? I used to have a 83 Volkswagon GTI, that had a plastic resivour, that was ment to take pressure. I was thinking of hooking it in to one of my heater hoses, and putting it as high as possable in the engine compartment, so there would be more pressure, to push air bubbles out from the bleeder. I do not like having the radiator fill spout so low. I am used to my 67 mustang, and 82 K20 with radiator fillers that are a good 4 inches above the top of the engine. They never had any coolant problems, but also the system is a lot simpler, and my tiny brain can fathom it a little easyer. I used to be a fan of the good old american cars, that guzzle the gas, but now I wish I could fuel inject every engine I come by. Well, I get off work today at noon (I love my job!) so I will start to swap out my trans. Wish me luck! Bob

astreamk1 · Nov 4th, 2005, 07:09 AM

why don't you just bleed the cooling system with the car up on a set up ramps ?

bob89sentra · Nov 4th, 2005, 08:49 AM

Thats what I do, I have bled the system every time I put it on ramps. (way too often in the last two years) I will try putting the thermostat in with the bleeder hole to the top, bleed the system, and retest the system for leaks. Hey on a side note does anyone know which way the coolant flows in this engine? Does it flow into the bottom of the radiator then out the top into the head, or the other way? I know my small block chevy is Ass backwards, and I hope that the GA16i isn't. Has anyone tried putting a thermostat in a different location, like an the lower radiator hose, I would rather have a regular single action thermo, than this $15 dual action one.

dreamteam · Nov 4th, 2005, 01:15 PM

As you probably already know, Nissan has designed a coolant passage to warm the gas going into these little buggers.
That is a liitle more sophisticated than your Mustang.
And....these cars get great fuel economy.

bob89sentra · Nov 7th, 2005, 08:04 AM

Quote:

Originally Posted by dreamteam

As you probably already know, Nissan has designed a coolant passage to warm the gas going into these little buggers.
That is a liitle more sophisticated than your Mustang.
And....these cars get great fuel economy.

Yup That is for shure, I get about 12-15 Miles per gallon in my stang, and above 30 in my sentra.

Well... I just did my swap from the stripped out 5 speed, to the 4 speed, and I was sucessful. It only took about 3.5 houres to do, plus about 1.5 houres to take the 4 speed apart to clean, and verify everything is good inside. The 4 speed came from my local bone yard, on a car with 210,000 miles on it, and I was amaized of how good all the syncros, and berrings looked! I hope this will last me longer than my previous bone yard trans (2 months).

Ok now for my overheating.
I had an idea come to me, I was thinking that my overheating, still could be my EGR, because when the engine gets warm is when it starts idling a little inconsistant. I was a little lazy, so I just unplugged the main vacuume line from the intake manifold, and I am not shure, but it does seem to run cooler (Meaning that I have not yet had it overheat). There are many things that hook to the manifold vacuume, and I will start to elimanate which ones don't affect the overheating. It still runs rough at idle, and I am not shure if that is from me unplugging the vacuume line, or if it is an entirely different problem.
Oh yah I did plug the intake vacuume with a vacuume cap in case you were wondering

Well thats all for now, thank you all for the help so far Bob

dreamteam · Nov 8th, 2005, 12:52 AM

Congrats on the 4 speed, sounds like it went well.

Keep us posted on the heat problem..........

SuperSentra4203 · Nov 11th, 2005, 05:44 AM

Forget the EGR, that's not your problem. Your left with one of two problems really. One is that B12 temp gauges really suck, both of my old B12's were highly inaccurate. Install the Autometer and you'll be very happy (I have one in my Trans Am) That'll also tell you if you are really overheating or not. Air in the system always shows one tell tale sigh, it smokes from your radiator cap... On to the second issue, just because the radiator fan is running, doesn't mean it's running at max rpm and giving the CFM that is needed to properly cool the engine, the fan may be on it's last leg. Also, cooling fan relays are know to have fits and do weird things when they get old. Remove it and test it to make sure it isn't junk.