Intermittent Heat...

S

skillet

Member
Location
Cornfields of Indiana
Well, with single digits outside now, I'm finding out that our heater will blow warm heat, and then after a while, go cold... Sometimes we have to shut the air off it's so cold. I had this issue with my MINI, but it was related to the antifreeze being low. Not the case here. Could it be the heater core? Thanks!
 
That rushing fluid sound we have discussed here on IS. It was related to coolant - air in the system. If you have had coolant flushed or replaced recently, this could be why.

There is a radiator valve on a hose on the passenger side near the firewall that you can open to let out air. When the car is cold, mark the level of coolant and check it every couple of days. Once the air percolates out of the system (which can happen with normal use) you might need to add a few more ounces of coolant. If not, then have a dealership get all the air out.

I have no idea why this would cause your heater to turn cold - unless the heater uses the coolant fluid as a heat source and the air bubble has become trapped in that part of the system? Might be a different problem than the fluid rushing sound.
 
jumbosrule said:
That rushing fluid sound we have discussed here on IS. It was related to coolant - air in the system. If you have had coolant flushed or replaced recently, this could be why.

There is a radiator valve on a hose on the passenger side near the firewall that you can open to let out air. When the car is cold, mark the level of coolant and check it every couple of days. Once the air percolates out of the system (which can happen with normal use) you might need to add a few more ounces of coolant. If not, then have a dealership get all the air out.

I have no idea why this would cause your heater to turn cold - unless the heater uses the coolant fluid as a heat source and the air bubble has become trapped in that part of the system? Might be a different problem than the fluid rushing sound.
Click to expand...

Thanks. I haven't had the system flushed since we bought it in Aug, but who knows what they did at the dealership...
 
if you just bought it August, then I would think they would help you out on this.

also the heater does use coolant for the heat source, thats why it takes awhile for it to really get warm. the gurgling noise you hear is not normal. hope you get it solved :smile:
 
Same thing!

Hey guys... New here... I need your help. I just encountered the same intermittent heat issue with my heating system. And it's cold as balls here in Jersey! Anyway, I did the whole flush thing and also changed out my thermostat believing that was the root of my problem. When I started her back up, same thing. No heat when she's at idle, only when I accelerate is when the heat picks up.
I don't have any overheating issues and I did remove the airvent valve when refilling with coolant... I'm baffled here... Please help!
 
Super annoying... Especially with it being cold out. Right now I'm reflushing the system. I hope it's not the heater core. Wonder if that can get clogged. But my coolant was very clean when I inspected it.
Again tho, it works fine when I'm on the gas. What can it be?
 
NaughtyNori said:
Hey guys... New here... I need your help. I just encountered the same intermittent heat issue with my heating system. And it's cold as balls here in Jersey! Anyway, I did the whole flush thing and also changed out my thermostat believing that was the root of my problem. When I started her back up, same thing. No heat when she's at idle, only when I accelerate is when the heat picks up.
I don't have any overheating issues and I did remove the airvent valve when refilling with coolant... I'm baffled here... Please help!
Click to expand...

skillet said:
Yup... I'm still trying to figure mine out. Doing the same EXACT thing... If you ever find a solution, please let me know.
Click to expand...

I have heard of this happening to the VQ35DE engine several times. My 2004 G35 only gave out heat at idle and I know a lot of 2003 - 2006 350Z owners that have this problem too. Even if you have your system flushed you can still have air in the system if the process was not properly performed.


Here are a couple of things to try:
  • Find the pressure relief valve on the left side of the engine. Slowly loosen it while the engine is still warm and see if any air leaks out.
  • Top off the coolant reservoir and drive around for a couple of cycles. Once cool, try to top off the coolant fluid again. Keep repeating if it keeps taking more fluid.
  • Jack up the front of the car (or use ramps, inclined driveway, etc) and let the engine run for a while to try to encourage the air to come to the surface. You can try this with the radiator cap off, but you will want to make sure you insert a funnel in the top of the radiator and somehow weigh it down so no coolant leaks out once the engine gets hot and the coolant starts to bubble.
I ended up doing all three over the course of a week and never had the problem again.
 
Bad to worse...

Well, after all day of bleeding and cooling and repeating to no avail, I decided to take a break from it. About an hour later, I had to step out and decided to take the FX for a spin to see if maybe it would help.

All was going as usual, intermittent heat upon acceleration only. I then got on the highway and punched it for a mile, and instead of the usual heat, it got cold... When I got off the highway, I approached and stopped at a traffic light and observed my engine temp rise! Being close to home, I baby'd her home.

At home, I immediately popped the hood and began to feel around. The top radiator hose was super hot, while the bottom radiator hose was cold. Now, I just replaced the thermostat assembly today. I find it hard to believe I got a defective thermostat unit. What could it be?

Before this occured, I was ready to replace my water pump next to see if that would fix my intermittent heat problem. Now I'm curious to know if my new thermostat just failed or is it signs of the water pump dying/dead?
 
Worst Case Scenerio

Let me tell you where I am at right now and just be forwarned that it aint good...

After swapping out the thermostat then the water pump, then the thermostat again, I got frustrated and decided to take it back to the dealer. They originally believed that it was just an air pocket and performed the work. Got it back a day later and everything was performing great. Nice hot air was blowing in the cabin and I was happy as can be again. But as I drove back into my home town, 15 miles or so, the heat disappeared and the engine began to over heat. :mad:

Called the dealer right up and took it right back. They then performed alot of tests and believed that it was possibly the radiator being clogged. They stated that they did a combustion gas test on the coolant and it didn't give them any results that it may be a blown head gasket. They did test the radiator and stated there was a flow problem and swapped out the radiator.

After the radiator was replaced they test drove the car for a while and stated that once again, air was getting trapped in the cooling system and it was once again making the engine temp spike and spew coolant out of resevoir.

So I am now left with two options...

Replace the head gasket and hope that will do the job or just replace the entire engine... Either way, Its gonna cost me $$$$$... F***K! :tdown:

So, I gotta figure out what to do and am requesting your help. New VQ35DE, Used low miles VQ35DE, Forged Bulletproof VQ35DE or Stroked VQ35DE???

Should I get the dealer to swap the engine out, or goto a performance shop? Not that many here in Jersey...

I was in the future going to upgrade to a Stillen supercharger for decent performance gains, but now with needing a new engine, it leaves the door open for everything...

Please help...
 
Skillet

Skillet, I think you may just have an air pocket in the car. My car started off like this last summer and I was ok with it because it would go away. But it got worse this winter and now I am up Sh*ts creek... :embarrassed:
 
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