Nissan Repair: 1996 Altima, radiator cap, head gasket

Question
QUESTION: Hi Calvin,

Well, the car is all put back together and purring like a kitten! Still having issues, though in a different direction. I'm pretty sure I know what needs done, but wanted to see if you had any suggestions for other things to check out while I was at it.

The car runs good and strong. However, on the test run today, it got hot. Makes sense in a way I suppose, since there was obviously an issue that caused the head gasket to go to begin with. Thing is, I clear forgot to check anything else, and I guess I forgot there had to be a problem to begin with.

What I am going to do now, is replace the water pump, and I'll tell you why to see if I'm on the right track, and I'll also give some other symptoms in case I'm looking in the worng direction.

First, as I understand it with these water pumps for this engine, they tend to go often, relatively speaking. There was as I said, a problem that caused the gasket to go to begin with. So, the next thing to do is to check that. When I had the motor running, I could hear sort of a rattling from the area of the pullys. Only thing I could think of was bad bearing water pump. Makes sense if over heating. Prior to noticing that though, and before the car ever registered hot on the meter, I had steam coming out of the radiator cap. Another symptom: NO HEAT. Thermotstat is good. I have the old one and the new one as well. Thought maybe the new one was even bad so brought them both in to the house for the old boiling water test, and both open just fine, so it's definitely not the thermostat.

So, water pump is the next cheapest thing. I'm also wondering about the steam coming out of that radiator like that though. Obviously the motor was hot at that point, but the meter was showing normal temps until late in the game when it buried itself in the red. So, I'm also thinking the system needs belched, and I'll do that tomorrow as well, so all that said, the symptoms and what I am preparing to do, are there any other things I should be checking while I am doing these things?

John

ANSWER: Hi John -

I am glad the car is running smooth now. As for the overheating, have you checked the fan(s)? I am not sure whether you have one or two, but one should go on after the engine reaches a certain temp, and the other should go on when the A/C is on. Let me know on this so I can tell you how to diagnose, as it could be the fan motor, switch, relay, or fuse.

If you hear a rumbling sound from the timing belt area, it is probably the water pump, so you are on the right track. Water pumps rarely go out unless abused, so check carefully -

Let me know how it goes -
aloha
calvin

---------- FOLLOW-UP ----------

QUESTION: Hi Calvin,

Fans are running fine. I changed out the water pump today, but in the end what I have is an extra. No biggy. I still hear a little rattling in the front near the pullys though. It's hard to pinpoint because it's intermittent.

I haven't had the car out since the overheating incident yesterday, but have run it a few times since putting in the new water pump. The latest time was a 15 minute or so run at idle in the driveway. It never came close to overheating, and just stayed in the normal range. In between running times and some during actual running, I've been opening the bleeder valve above the thermostat to bleed the air out. Thing is, besides the eventual getting hot, I'm thinking that screw shouldn't be messed with when it's running. I kind of get the impression I'm actually letting air in when I do. Any thoughts on that?

So, I have so far eliminated the thermostat and the water pump. The coolant appears to be flowing OK. I'm finally getting some heat out of the heater, but it's actually lukewarm and not really hot air.

I plan on driving it around the block a few times tomorrow to see what happens, but something that concerns me, is it's like water is boiling back into the reservoir, which I read somewhere can either happen when air is in the system, or when the head gasket is gone..... Surely to heavens not that, because we were very careful this time around and followed everything to the letter. I'm not seeing oil in water/water in oil this go either.

Additionally, the engine for all accounts appears to be running perfectly fine, though I'm not so sure 15 minutes was enough to decide whether it was going to overheat again or not.

Anyway, your thoughts are greatly appreciated and highly valued.

John

Answer
Hi John -

Well, it looks like you have gone through the exercise. Hopefully the car will run better (cooler). Take the car for a spin and see what happens.

As for the bleed valve, Yes, the best way to use that is when the engine is cold and you are filling coolant in the radiator. It prevents air pockets before the thermostat while it is closed.

Thanks
calvin