ayoung101

it finally got cold here in michigan, and suddenly my heat went out. on top of that, a few days later, my engine temp started going higher than it's ever been. it didn't get into the red, but it's always been lower than where i thought it should be on the temp gauge (even after i replaced the thermostat a few years ago), and now it's a little higher than where i imagine it should be. on top of that, all around the same time, my idle position started phasing higher and lower every time the engine is cold (assuming problem with TPS).

i hear there is a valve somewhere related to the heater core. i have no idea where it would be or what it would look like. is there any possibility these 3 things could be related since they all happened within a week?

da_bigg_wigg

Start simple. Check coolant level, and work up from there.

GV27

Thermostat, perhaps?

ayoung101

i'm guessing thermostat for the overheating thing, but would that affect the heat? i mean, i could see it affecting heat if it was stuck open and never heated up, but not vice versa. . . . .

i'm not too concerned with the overheating thing. especially since it is winter and at the very least the cold air blowing on it keeps it cool enough to drive. and in the warmer months i have a motorcycle and a geo metro to drive. but i gotta have heat!

norcalsvx

lazy t- stat? check 4 crawler website

gonzo

X2 on check the coolant level.
And the heater temp. valve is on the firewall. Can't miss it. Heater hose on both ends and a cable.

da_bigg_wigg

Just check the coolant. My old civic had a leaky rad hose, so it would over time lose coolant. It lead to warmer than normal operation and decreased heat output, which just so happen to be the same symptoms as yours...

ayoung101

it doesn't leak any fluids. which actually just made me think of an even scarier thought. i hope it's not leaking coolant into the oil. . . . .better go check for milky fluid in the crank case. . . . .

spudrunner

My '88 22re heater started blowing cold 2 years ago. It wound up being the headgasket at 137.000mi. Hope yours is a simple fix!

milowilli

Check the heater valve on the firewall . You will see 2 hoses going into it and a wire from inside which opens and closes it. Somtimes the wire slips off and the valve does not work.

slater442w30

First thing, change the thermostat, we do about 10 of them a week at my shop during the beginning of the cold season. Yours is probably sticking shut. That will also decrease water flow through the engine because the second biggest hose in the system is shut closed. Then find the little valve for the heater core, take it off, clean the crap out of it, re- install and zip tie it into the open position, worked wonders on my 87 runner, also flush the heater core while you have the hoses off, flush both directions with a garden hose back and forth until the water comes out clear.

I am like you, Heat is not an option although the guys I wheel and work with think it is.

Justin311

I am experiencing a similar problem and wondering if you've ever seen this with the heater valve....assume the truck is warmed up to operating temperature, and you have the temp on full heat, but the fan off. Flip the fan on and the heat comes out nice and toasty, for about 5 seconds. Then the temp drops about 30 degrees and slowly the heat dissipates till its blowing luke warm.

If you turn the fan off, then back on again, it will do the same.

Can anybody tell me what to check? You would think the heater core but it is so strange it kinda "stores heat" then loses it when the fan blows over it?

yukonwheeler

my 87 4runner blows somewhat warm air from dash/defrost vents unless on recirculate then it gets a few degrees warmer however it blows hot air from the rear heater reguardless of having the front heater on.

aswell it also blows hot air befor the front heater even hints at getting warm this is my 6th toyota
and the coldest one to date .

new thermostat blocked off the rad and topped up coolant. i did just finish a timing chain rebuild. bought the truck broken for a 100$ with a no start so no idea what heat was befor.
no coolant leaks no coolant in oil.

i live in the yukon and it -20 -30 these days so heat is not an option need it to see AHHHHHHH.

annoyingrob

You don't have enough coolant flow through your heater core. With the fan off, there's nothing to pull the heat from the core, and it will slowly reach coolant temperature through the small flow, or just through thermal conduction with the rest of the heater system. Turn it on, and the fan will essentially pull the heat out of the core faster than it can be replaced, and your temperature drops.

First make sure that the control valve on the firewall is opening and closing properly. Slide the temperature fully cold, and look at its position, then slide it fully open, and make sure it's moved position. Sometimes the wire thatmoves it can come disconencted in the dash. Next, remove the valve, and clean it out. I like to soak it in CLR for an hour, then scrub it out with a brush. Then flush the heater core. I like to use an aquarium pump in a bucket, and pump water/CLR backwards through the core for an hour or so, but a garden hose works too. Make sure to pump into the return (The one on the passenger side, the one without the valve.)

toyota hunter 07

Had a 89 p/u and valve cable broke mid point somewhere ..... And had the same symptoms as you .. Cause it broke h 1/4 open.. So i was getting some heat then it would slowly cool off....so i installed an old school manual choke cable kit....after months of opening and closing it manually under the hood like a j@%$@#@$ss...but this was a quick fix for a plow truck ..if its your daily drvr replace the cable............