88 Nissan Sentra Heater issue

Hello, I have a 1988 Nissan Sentra that I bought about 4 months ago. It has A/C and during the summer, it was great....nice and cool. Now that it's winter, it's a whole different story. The heater blows air but with no heat what-so-ever. Basically, it's the same as the fan just turned on with-out the A/C button switched on.

The strange thing is that the heater core doesn't seem to be bad. The car doesn't loose coolant. I check the coolant every other week and don't think I'ver ever had to add any anti-freeze. With the engine at operating tempature I can grip the hoses that go to and from the heater core, they are never hot. I've thought about changing the thermostat, but if the thermostat were bad wouldn't the car over-heat? If the heater core was bad, wouldn't the engine lose coolant?

Can anyone please help?

Reply to
David
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Give me a e-mail and I'll send what I have on your heater...

Reply to
Helpmelearn

My e-mail is snipped-for-privacy@writeme.com

Reply to
David

When you are feeling the hoses to see if they are hot also feel the hoses going to the radiator to see if they are hot. Thermostats can fail open so that the engine never gets up to temperature.

If the engine is hot but the heater hoses are cold then we know no water is circulating through the heater core. Some cars had a valve in line with the heater core that turned off the hot water when it wasn't needed. Does your car have one (not a trick question, I'm just not familiar with this model)

If you don't have flow and there is no valve or the valve is working properly then the heater core is plugged up. I have had good luck cleaning them out by disconnecting both hoses then using a garden hose to backflush the heater core. Amazing how much crap will come out of there. Be forewarned that if you have a heater core that is on the verge of springing a leak the waterhose flush could push it over the edge.

If you aren't able to flush the heater core well enough to restore heat then you would need to replace it.

Steve B.

Reply to
Steve B.

Obviously the heater core isn't doing it's job in terms of getting hot. With a car at the age yours is, it could be that the heater core is plugged up due to infrequent maintenance, or it could be a thermostat stuck open. Do either of the radiator hoses get hot? How about your temp gauge, does it move off of the cold mark?

Chris

Reply to
Hal

Steve B.,

Thank you for your response. I think I once also felt the radiator hoses and they were hot. I'll check them again today. As for a valve that shuts of the hot water, I do not know if this model has one. I'm going to the local auto parts and check a manual. If the manual doesn't mention such a valve, I'm planning on doing three things today if necessary. (1) I'm going to remove the thermostat and see if that will get the heater core's hoses to get hot & hopefully get the heater core to blow hot air. If it does I'll put a new thermostat in. (2) If after that no heat comes out I'm going to do your garden hose trick to see if it's plugged. (4) If it un-plugs the heater coer but also blows it out, I'm just going to bypass it as I have no hot air as it is and on Autozone.com the heater core is $399.99!!!!!

Once again, thank you.

David

Reply to
David

Update on the situation. I removed the thermostat housing and discovered that the car didn't have thermostat. I bought a 180 degree thermostat, installed it and the car came up to tempature much quicker. However, the heater still won't blow hot air. I can still feel the heater hoses and one (the lower one) is luke warm and the other one (the higher one) is completely cold. Since I don't have to add anti-freeze and there are no leaks, I'm going to assume that the heater core is plugged up.

My next plan is to un-plug it by connecting a garden hose to the higher heater hose (disconnecting the lower hose of course) and seeing if any junk comes out of it. This was suggested by Steve B. Does anyoone have any other thoughts on another way of un-plugging it???

Chris, to answer your question, the gauge does get off of the cold mark (even before I installed the thermostat). I't may help that I live in Southern California. However, last night I had to go to south San Diego near Tijuana, Mexico and it was 46 degrees at 9:30 PM...which to me was freezing.

Reply to
David

Sounds like a air pocket or plugged htr core. the hose trick works excellent and I have also had luck with the product CLR used for cleaning bathrooms, but it works exceelnt on heater and rad cores. try running it up to temp without a rad cap and see if there is air bleeding off

Reply to
Helpmelearn

This is good. Odds are you'll see better mileage with the thermostat in there, too.

Either the heater core is plugged up, or the valve that allows water through it is not opening. The valve might be worth checking right off if it's easy to get to, but on some vehicles it is a nightmare.

This is a good thing to do. Another possibility is to run a radiator flush through the system. This will clean out a lot of gunk, BUT if the flow through the heater is completely blocked it won't get in there at all. Also, of course, if your heater core and radiator are held together with corrosion (like on many old cars), running the flush through it will make them leak. On the other hand, then you know they are overdue for replacement.

--scott

Reply to
Scott Dorsey

Update.

Yesterday I tried the garden hose solution and....it worked!!!! First I disconnected the bottom heater core hose at the heater core and the upper heater core hose at the back of the thermostat/distributer housing. Very little water came out. I put a funnel on the top heater hose and poured CLR through it. It cam out of the bottom exit of the heater core just about as fast as I poured it in. Next I connected the garden hose to the top hose of the heater core using a garden hose repair coupler. It urned it on and clear water came out of the other end. Here comes the interseting part: I then reconnected the bottom hose of the heater core at the core and removed it from the other end. I connected the garden hose to it (the bottom heater core hose) and turned on the water. The garden hose loaded up and very little dirty water came out of the top hose of the heater core. So I turned up the water on the garden hose to it's limit and placed my thumb over the exit of the top heater core hose. I let preasure build up and I removed my thumb. Water would spurt out and return to a a very small flow. However, after doing it over and over again about five times, it seemed like a cork popped out and the water started shooting out full blast. Nice clear water. I then hooked up both heater core hoses, turned on the car, let it reach operating tempature, and...... some heat! Just a little. However, when I drove the car the heat became much stronger.

I next want to do a full coolant system flush. I imagine there must be all sorts of junk in th system. Can anyone suggest the best way to do a flush?

Reply to
David

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