I belive my heater core is clogged up. One of the lines going to the heater core will be warm and the other cold, plus my cooling system is finding the weak spot and causing leaks. I've replaced two small coolant lines and one going to the heater core. Now I have another line leaking, no heat unless accelerating and one line to the heater core hot and the other cold.

Is my heater core clogged?

I think so but before I bypass it I would like a some opinions.


Thanks

 

did you check the heater control valve?(i think thats the correct term for it) sounds to me like its pushing the hot air to the valve control but i guess its not opening up to allow the air through to the vents like its supposed to...mines went bad all of a sudden...found out when i cranked my car up turned on the heat and puff of smoke from under the hood...turned out mines was clogged also and my valve control had gone bad lol 2 things at once? just my luck lol but check and use your FSM if you have one...i honestly dont know the proper procedure to check it myself. GL with the problem finding tho...heater cores are a pain to replace and our 3rd gens have a crapload of hidden screws and crap throughout the dash pieces lol

 

the heater control valve has been bypassed. I have the line running from the engine to the heater core.

 

Try flushing water with a good amount of pressure opposite of the flow natural to the heater core and you may unclog it, which is probably what your problem is. There are more than one thread announcing this problem and the techniques related to solving this issue. Help us consolidate the already cluttered forum. thanks
One of them:
http://forums.maxima.org/3rd-generat...e-culprit.html

 

which one of the inlets is opposite the flow of water into the heater core?

 

Never mind, heater core is clogged. Top is going into heater core and bottom is comming out. Top hose is hot and lower one is not.

This makes sense after replacing my radiator and seeing how clogged it was.

Thanks.

 

The cold hose, and have you bled the system? Again, I bet you will find some good info and techniques to diagnose this further by reading the older posts. Check them out, a few of us dealt with these issues when the weather became cold, and we all collaboratively figured out what to do. Often the case, a good bleeding was the fix, but in your case, try flushing it out by pumping water from a water hose (not too much pressure is advised as one would get from a pressure washer) and simply direct the flow into the bottom outlet and see what comes out of the top. Once a blockage occurs, it festers, and these may often spring up from spring and summer projects where coolant is drained and an air pocket is left in the heater core, since it is the most superior location of coolant flow in the system.

 

ok which one of the lines comming off the block is the "out line" to the heater core and which one is the "in line" from the heater core back to the block?

I bypassed the heater core but did not mark the lines!

Thanks.

 

and its not the heater core. I ran water through it (reverse flow) and it flowed fine. I have a air pocket somewhere!!!

 

It is in the heater core! I feel I have on too as today my air was cold while sitting and hot while moving. I luckily don't have to drive my car at all, so it's no big issue right now. I have been told that the best way to bleed it is with a Prestone Flush Kit, but it involves cutting the feed hose (top one) or just using two hoses with a barb. The kit allows you to raise the point in which air collects in the system so one can bleed it with ease. I haven't tried, but I think my setup will offer the same kind of procedure for bleeding.


I think the send hose connects to the port coming from underneath the intake manifold and the return connects to the intake manifold.

 

thanks for the reply. this morning I disconnected the hoses going to the heater core but did not mark them (they are aftermarket and run straight to the heater core)....from what I remember there is a line "on top" and a line "on the bottom" by the engine.

Are you saying the send hose is "on the bottom" and the return hose is "on top?" This is of course connecting to the intake and engine block area.

Thanks.

 

Yes, I am pretty sure this is the case, because of what this picture reveals to me.

You can see the "lower" pipe closer to the block here, coming from the water pump, which would make sense that the fluid is being sent from the pump. The "upper" pipe going into the intake would be the return if the logic above is true. Happy you don't have to tear down the dash to replace the core, but be very ample and thorough when bleeding as it is a very aggravating to do over and over again. I recommend creating a higher location for the air to collect, like Ben used created with the prestone flush kit, or as I did with the T shaped barb to make it easy. Search Prestone flush or Prestone flush Kit to see what Ben did as he described it thoroughly in another thread. He has Satan's breath coming out of his vents too.

 

IMHO you raise a couple of issues: 1. Hot/Warm side of heater core will be supply side, water pump is providing pressure. 2. When you say no heat unless accelerating do you mean, prolonged acceleration, or, as soon as you let off the throttle the heat changes? The second option may indicate a problem with the vacuum line routing... Anyone have experience with this?

 

It appears that the heater control valve has been bypassed, as mine as well, and I experience the same behavior. A good bleeding is all it needs alot of the time, and it's a very particular process which can easily be ridiculing towards ones morale and ego. The link previously posted describes, in more detail, the proper way to solve the troubles associated with heater cores. The mention of reversed vacuum lines is there as well, and everyone includes some good fixes for simple troubles with the heating system. Enjoy the forum, and enjoy the search function even more, because it truly is your best friend!

 

well my heat is kicking so hot I cant keep it on 80 degrees without it becomming uncomfortably warm at time in the car.

This is what I did. When I replaced the heater hose lines from the block to the heater core, I got a set of lines that are 5/8" and one set 3/4". I used the 5/8" for the heater core end and the 3/4" hose for the engine block end. Of course nissan makes the hoses two different sizes so you can buy the hose from them.

To make them mate up, I got a NPT fitting from home depo, one end 3/4" and the other 5/8" some clamps, teflon tape and a screwdriver to make my new heater core lines.

I decided to disconnected the feed line to the heater core, hold both ends up above the dash level and radiator level and stuck a funnell in the line feeding the heater core. I then began to pour antifreeze into this line until it began to come out of the sending line from the engine block area. Needless to say it took a good amount of antifreeze and pouring it in at an angle helped to let the air escape. It is fill to the max and the heat is working very well.

Thanks for the tips everyone.

 

and this was done (topping off colling system via heater core lines) in the a.m. on a cold engine with no pressure built up in the cooling system.

 

Awesome, I am happy to hear that you were able to bleed it successfully, and in the process create a useful escape for those of us who need an easy way out sometimes; if only these were more frequent with older cars, but once again, we run into an oxymoron.

 

I topped off the car a total of 3x, all in the morning on a cold car. Seems like air, if any will tend to hide at the heater core level since its mounted pretty high up.