Heater blows cold after 10 seconds. Advice needed. (1 Viewer)

[EvanD]

Hi gang,

I've just spent a good amount of time with the search function and come up relatively empty regarding my issue.

My heating system blows cold not for the first 10 seconds or so. If I turn it off, drive around, and turn it on it blows warm for the first 10 seconds. After that though it goes straight to cold.

Auto heating systems aren't something I have any experience with so any input on where to start would be extremely appreciated.

Edit- The truck runs at healthy temperature in all conditions and the AC/vents appear to work just fine. It also worked when I first got the vehicle and randomly stopped two winters ago. My situation was such that I didn't need it so I haven't tried to deal with it until now.

Another edit- Rear heat doesn't work at all. Not even for the 10ish seconds.

Thanks in advance,

Evan

 

[White Stripe]

Check your coolant level, it is likely low and you likely have a coolant leak somewhere.

 

[kowalski]

your heater core is probably plugged

edit, just realized both aren't working. The guy above me probably got it right.

 

[EvanD]

I'll check that out tomorrow and report back. Thanks guys!

 

[EvanD]

I take it back. Curiosity got the better of me so out came the headlamp.

Coolant level is not low. In fact, it's a decent amount over (about halfway from the full line and the top of the tank). I can't imagine that's causing the issue?

Edit- I also haven't been filling it (a shop would have been the last to do it, and it wasn't recently) so a leak seems unlikely.

Any other thoughts?

 

[Rivman1243]

Is the heater valve actually opening?

 

[EvanD]

Unsure on the valve as I haven't personally checked. I kinda figured the fact that it blows hot for 10 seconds meant that it was but in light of more searching after I posted this thread I'm going to check.

I still can't find any very similar account of my situation (where it blows hot and just stops) but it seemed worth checking.

 

[gnarlytoes]

Probably heat control valve is not opening all the way or blockage in line or core. It is open just enough to let a little flow through. When you turn the heater on, it quickly cools the heater core off and not enough flow to keep it warm.

 

[Bigsky80]

I had a similar problem that ended up being a missing thermostat o-ring.
Cheers,
Scot

 

[Wayne]

I'm not sure what exactly is causing you to have heat for ten seconds and then cold. The cooling/heating system can get air trapped in it that needs to be "burped" out. Park on an incline (nose high), take the radiator cap off and run the engine a normal operating temp with the heater turned on for ten to fifteen minutes. This will allow any air trapped in the coolant/heating system to escape. This procedure has restored heat to a few Cruisers.

 

[baselfish]

are you indeed familiar with the HCV ??? tis dead center at the back of the engine bay

the trouble it if it is an original part with some 200K miles - it is highly susceptible to completely falling apart -
then (lest you have enough 3/8 hose to do a emergcy bypass) you are SOL till you replace it...

general rule of thumb (lest you are intent on replacing it and have the new part in hand) is to NOT money with it -
again especially if it is old.

if you do want to test / inspect it - gingerly loosen right side clamp (you might get some coolant spillage but it is safely at the apex of the cooling system) and manipulate the HVAC slider in the dash from cold to hot - it is basically a mechanical linkage -
at cold the HCV valve is closed and at hot is should be fully open.

BTW Don't crank over you engine - lest you want to spew coolant all over....

hopefully it is you HCV - and from there it is an easy replacement (I got an autozone part for $40.00)

if it does turn out to be your HCV - indeed follow the aforementioned post on "burping" the system - as you have open up the system
to air....

Bf

 

[LandCruisinMy93]

I'd suggest burping the system which can be down on flat ground also with the use of a funnel, some electric tape and some coolant. Get one of the Walmart funnels that has the screw on rippled flew hoses and cut the neck out at the bottom of the fist set of threads. Place it down into the radiator neck, if it's a tight fit like some are leave it otherwise wrap a few wraps of electrical tape around it until it's a tight fit, run your engine until warm and fill the funnel halfway with coolant. Open your heater valve. Proceed to squeeze all the upper heater hoses repeatedly watching for escaping air and dropping coolant level. When no more air escapes idle your engine up to about 1500 Rpm and hold it there while watching for escaping air and coolant drop. When no more air has come out for about 5 or so minutes s*** the cruiser off, pull the funnel up slightly to allow excess to drain through the catch tank orifice. Reinstall radiator cap and check that your heat is working again. If not the likely culprits are Heater control valve is internally broken ,thermostat not working properly and the bypass is carrying coolant, the heater core is plugged and needs a back flush.

 

[thebigredrocker]

Found this on youtube:

 

[izzyandsue]

This is how I did mine if you find out you need to clean up heater. When done, it went from tepid warm to hellacious heating. The funnel is the yellow one on the pictures. Heater was blowing 150F sitting on the driveway.

Heater Core Flushing - OWNED!

 

[EvanD]

Awesome.

Thanks for all the input, guys!

I won't have time to get into it tonight but will start going through all of this tomorrow.

Cheers!

 

[Wayne]

Well Evan, what did you find?

 

[Squash]

Have you opened the rad cap when cold and looked into the rad or are you looking at the overflow plastic jug.
Fill the rad, start the vehicle and then grab the upper rad hose squeezing till air is gone and only fluid rises in rad cap neck.
You will also want your thermostat to cycle so make sure the engine warms up while rad cap is off, again squeezing the upper hose and adding fluid if required.

 

[EvanD]

Hey gang,

Been away from the computer for a few days but removing the radiator cap and running it for 15 minutes seems to have remedied my issue.

The heater still doesn't blow as hot as it sounds like some do so I may try the system flush at some point but it was a nice quick fix until I have more free time.

Many thanks for all the input!

 

[Wayne]

Happy to hear you have heat. I probably need to back flush my heater core also......put it on the "to do" list.

 

[mod5csi]

Sounds like you have air bubbles. Park on an incline or jack up the front end so that the radiator cap is the highest point in the system. Make sure the heater is on high, the heater valve on the firewall is open and turn on the rear heater.

Warm air for 10 seconds then cold is a lack of flow through the heater core. Likely air bubbles.