bobotech

Okay, my daughter has a 90 maxima, 5speed, ac, etc. SHe has never had heat in the car since she got it a year ago. The a/c works fine and everything else works fine except heat. The car is running great and had a complete tuneup about 5 months ago.

Here's what has been done, new thermostat replaced, system flushed several times with flushing chemicals (I'm taking a guess that someone used Stop Leak in this system because the radiator was repaired). I know that stop leak can cause heater cores to plug up so thats what I thought was happening.

I also did do the trick of lifting the car about 3 feet in the air, let it run with the cap off and filled it up that way (trying to bleed the air out).

Well this past weekend, a friend and I tried to replace the heater core. We spent about 7 hours on the car, we actually got to the point where the entire dash was off the car and we could see the heater/ac/fan assy and we were trying to remove it. Well we didn't get it off so we just put everything back togheter since my daughter needed an operating car. Well we decided to back flush out the heater core anyway.

So what we did was put a hose on the bottom outlet of the heater core and removed the hose from the top inlet. WE then filled the hose up with water and we gently used my aircompressor to blow the water backwards though the heater core (i know that can blow small holes in the heater core but she has no heat now so if worst came to worst, we could bypass the heatercore until she gets it repaired).

Anyway we flushed it out several times and it had plenty of flow. The water would pour/spray out the top inlet when we blew into the bottom outlet. It finally came clean after a bit.

We then hooked everything back up and tested everything, still no heat at all.

Now for the really odd part. The max has 2 hoses (obviously) going to the heater core. One of the hoses (bottom one) is the outlet and the top one (inlet) has a vacuum operated valve that i'm assuming stop or allows water to flow though the heater core. We then took the inlet hose off (while the engine was runing and warmed up, Temp gauge during all our tests was working fine and was at normal.). The was almost NO coolant flowing out the inlet hose.

We then removed the hose BEFORE the valve, still hardly any flow at all, as far as I am concerned, the danged thing should be spraying coolant all over us (the system WAS pressurized, we cracked the radiator cap and it did start to spray).

If we moved the inlet hose lower, we did get flow but just a gravity type flow, no forceful pressure flow.

The water that did pour out was hot (not sure if it was very hot or not, wasn't going to find out).

So now thats where I am stuck. I have no idea why there is hardly any flow out of the inlet hose into either the valve or the heater core. We traced the hose back to a metal pipe that goes under the intake manifold but thats as far as we went.

Also the car does have new hoses installed and what not.

Can anyone give me any good advice? I know the search function is disabled so I couldn't research the issue here very well and the Nico forums don't have much info as well. One thing i did learn is DON"T attempt a heater core unless you have checked EVERYTHING else out first (which we didn't LOL). I'm actually wondering if the heater core will be fine once we get a good solid flow of coolant to go though it.

89maxaz

I'm having the same problem with my '89. I'm going to flush the cooling system tomorrow, and check that valve you're talking about. I PRAY that I don't need a heater core!

Thanks for the heads-up. Good luck with yours!

|Bijan|

iTrader: (12)

wow, I had the EXACT problem w/ my 90. Seems like you did more than me...and still couldnt find out whats up. I thought it was the heater core....but I guess not

89maxaz

Anyone know the name of that valve? How sore's my butt gonna be if I buy a new one???

SOUL FLY- is yours fixed now, or not? You said "had that problem"...

internetautomar

iTrader: (30)

heater control valve

Wiking

Good advice ...no. just a guess:

"We traced the hose back to a metal pipe that goes under the intake manifold but thats as far as we went."

This hose [or the channels supplying to it] is blocked as you do not get adequote flow. It might be collapsed inner hose?
Take the hose out to verify its condition or test waterflow through it while its in place, both ends open... [now water should sprout out from engine]

Gas bubbles are sometimes very nasty, but does not sound like that. On some vehicles you need over half hour drive [while loosened leaking hoses] to get air off the system and water flowing.

-shock211-

iTrader: (1)

it's the water c o c k valve

bobotech

Well the thing about my daugthers car is that we were getting no flow from the hose before the water valve. I was figuring that maybe the valve was not working which is why we removed the hose at the vavle inlet, not the outlet (which then goes to the heatercore inlet).

We jsut get barely any flow out of the hose,this weekend, i'm going to completely remove the hose and see if it has collasped. But does anyone know where that metal pipe goes to? And maybe a diagram of how the heater system is setup on these cars?

Wiking

"But does anyone know where that metal pipe goes to? And maybe a diagram of how the heater system is setup on these cars?"

Chilton Haynes does have a pic. Could send it over if I knew where to...

There is a small alu block containing the tehrmostat bolted to the engine front end. From that runs two metal pipes between the two cylinderbanks: the small one turns towards the cabin [just above gearbox], another bigger one to radiator. This small one is the cabin hot water input I suppose. Disconnect here and test...

Has your car ever been warm after the overhaul? Maybe there is wrong kind of seal somewhere [thermostat housing/metal pipe connection] totally blocking the circ.

rpcraft

having gone through all of the same sypmtoms you experienced I can hopefully save you some time. The water pump is the most likely culprit, if you have checked the heat valve and thermostat and found no problems. I fought with mine for 3 cold winters, and upon changing the timing change, when the waer pump was changed out, I found the impeller blade to look like the lid of a tin can. Someone before me had used straight water, and I guess the stell on the impeller is untreated. I changed the water pump out and found the results to be immediate, and 100 % great, then of course the heater core started leaking. Next week will be devoted to fixing it and replacing my distributor.

Wiking

First time ever heard of such thing: I would guess that with bad pump you had overheating in the summer....

Can you give the specs? What type engine, car, model u have?

90pearlSE

I had this problem with my last Maxima and it was the the water **** valve (located on the firewall, close to the oil fill cap). Have you tried to manually open and close the valve? It works off of vaccum, and the default position is closed. Since I was in the process of building another max, I didn't fix it. When it was cold out, I just put the selector over to full hot, popped the hood & opened the valve (pull it towards the passenger side). As long as I left the selector on full hot, the valve stayed open for me (I just regulated the temp with the fresh air control and recirculator). If it stays in this position and you get heat, you've found the real culprit - I think you'd have noticed other issues if it was the water pump.

Wiking

He took the tube off - cannot be the valve. Most propably the pump or smtg blocking its outlet pipe.

See also: http://www.cardomain.com/memberpage/748507/7
http://www.cardomain.com/memberpage/748507/8

Psubird83

Well let me add myself to this list faulty heaters, today i fushed my whole system changed the thermostat and ended up the day with A overheating and none working heater still, i played with the check valve but to no avail, i either have a air pronblem, or a faulty valve, or maybe the water pump, so idk well see what tmrw brings, i pe i can fixit before i have to go back to school which is a 5 hour drive =-/

Psubird83

well now i feel like an idiot, i put the thermostat in backwards, duh, and refilled the coolant, and i beat the car pretty good so i could get a flow, and the heater finally started working wow so i think its only a matter of time before everything starts working again thank god

Jackrabbit

As far as I can see from as far as you have traced it. It has to either be a blockage in the line or the water pump. I could see the pump blades rusting down some and that affecting the heater. I have had that happen on an old truck I had. Anyway good luck.