MinimusMaximus

Throughout the year this usually isn't a problem but temps in my area have plummeted to the mid-high 20's and its really cold out.
My car never did put out blazing hot heater temps and it also is really slow to warm up all the way. I have to drive several miles before the temp gauge starts to climb then several more miles before the heater outputs high enough temps to take the chill off. 10 miles later and on the open freeway its finally warm enough in the car I can take my gloves and beanie off.

When at operating temps the needle is right in the middle. I'm wondering if I could put in a different temp thermostat to increase heater temps or is there anything else I can do?

94 Civic Si

Tell us about your car - year? Model? Swap? Stock?

mk378

Check that the air door and the water valve are moving to the full open position when you put the dash control on full hot. On 1997 or earlier this system uses mechanical cables that can break or go out of adjustment.

Both heater hoses should get hot when you have the engine warmed up and the heat on full. If only one is hot, there is a restriction in the core or the water valve is not fully open.

A new thermostat wouldn't hurt. Sometimes they don't close all the way, causing delayed warmup. Use an OEM one with stock temperature. While you have the system drained, disconnect the heater hoses from the engine and flush the heater core with plain water from a garden hose.

eghatch9295

iTrader: (1)

many thermostats are designed to fail open, very possible here.

TomCat39

One thing to add to all that has been said so far.

If your heater core has been replaced, if it's a 3rd party economy core, it can be an all aluminum heater core and a little smaller. The OEM one is larger and copper.

These two details I've noticed really cause the heat to suffer until the car is driven significantly.

I found the heat drops even just sitting at a red light at -4C or -6C. That can be another factor in addition to everything else already mentioned.

Of course in my area, the price difference was 100 bucks for aftermarket and closer to 400 (360+) for OEM.... What do you do?

youstolemybeer

if the temp gauge takes forever to climb, that is usually a bad t=stat.
block off the radiator with some card board, about half way and go for a drive, If the temp gauge climbs and you have good heat, then its the definity the t-stat

4drtegra

Had the same issue and it was the thermostat. 100% completely deteriorated seal. Replaced in 15 min and heated up perfectly.

Make sure you go OEM Honda on the thermostat. The aftermarket ones are crap

tony_2018

alot of members here argue that.

MinimusMaximus

Thanks for the replies.

This is a 1995 2dr civic. Manual everything including heater controls.
I thought it might be the t stat but wouldn't that just affect the engine temp warmup time? Once up to temp the tstats open and the gauge is at NOT it should be letting the normal flow of warm coolant through to the heater core right?
I assume the heater core is original? I've owned this car for about 5 years and haven't done much but regular maintenance.

If I were to replace the tstat as a first step and go OEM, are we talking dealer part or can I get an OEM from someplace like Rockauto.com?
I'll also check the mechanical controls. I know when the hot/cold mixer is all the way over to hot side it stops about a 1/4" from bottoming out against the slider rail. I can physically slide it over another 1/4" to the end of the slide but then it springs back. It does feel like its being hung up and the cable is not allowing it to go that extra little bit to the end.
I never thought 1/4" would make that much difference in how much cold air it added to the mix so I never messed with it.

Of course its freezing out now and all these little things are starting to matter.

TomCat39

The reason this is the most likely issue is...

These engines dissipate heat VERY efficiently. During winter, the cooling fan almost never, or just straight never comes on.

So, with the coolant constantly flowing through the radiator and the heater core, the engine actually never gets up to true operating temperature. The coolant stays at lukewarm temps and you don't feel heat with the cold air outside knocking what little heat the heater core was getting.

OEM you can't get from rockauto. Either Dealer, or Majestic Honda online parts or HondaPartsNow.com

Thermostat is one of the parts I would stick with OEM. Many aftermarket thermostats have a different opening spec and so the car doesn't run quite the same as the ECU is programmed to an OEM thermostat temperature specifications.

I was just adding the heater core if you've already replaced your thermostat and were still having problems. This would be another possibility, but does not describe the long time to come near operating temp like a failing thermostat does.

youstolemybeer

They way I understand it the thermostat opens but the frame around the thermostat (the circle around the part that moves up and down) acts as a restrictor slowing the coolant so it absorbs the heat of the engine, the engine operates best at about 170-200 degrees.. If you have either a thermostat stuck open or a path for the coolant to go around the thermostat you will never warm up.

TomCat39

Earlier in the thread it was noted that some thermostats are designed to fail open.

It's my understanding that the thermostat stays closed (to restrict coolant from going to the radiator) until the coolant reaches a specific temperature. Then opens to allow coolant into the rad which then drops the temp and the thermostat closes again to repeat the cycle.

If the thermostat is stuck open, the coolant isn't restricted enough to allow the coolant or engine to come to full operating temperature as the coolant is cooled through the rad and heater core faster than the engine can heat it up during cold winters.

I think this is what you were saying and we're saying the same thing?

eghatch9295

iTrader: (1)

as far as the ridiculous oe thermostat debate, i've been using stant thermostats for ever, no problems

DumpdEJ6

Same. Not to muddy the waters but just saying, I've used them almost exclusively and I have had zero issues with them.

MinimusMaximus

Thanks,
I just ordered a t-stat from HondaPartsNow. I'll drop it in once it arrives and update with results.

TomCat39

I wouldn't necessarily say ridiculous per say. It's definitely good know that stant brand is a quality OE alternative.

I think others have gone with whatever cheap thermostat the local parts store provided them, only to end up having issues with them. Then testing them and find they open prematurely or open at higher than OEM temperatures. Both of which will change how efficiently the car runs.

Really not to much different than the ball joint selection. You have OEM which you know is good, some good aftermarket brands and several junk aftermarket brands.

Knowing what is good currently is key. Stant is good on thermostats.

eghatch9295

iTrader: (1)

stant premium (appx 11$), are designed to fail open. they're the ones i use, and have always used.

tony_2018

I swear we had a parts thread for that info to be put in...is it stickied?

TomCat39

Not sure, we may need to look for it and we can go from there.

Made an error! Please see below for my gross error
I said the aftermarket aluminum heater cores don't appear to be as efficient as the more expensive OEM copper cores.

I believe this is in error. I found out the hard way that I've been loosing coolant. Finally got a big enough pocket to cause the idle surge and last night, an over heat. Discovered the problem hose today after the coolant splatter dried and some spots still wet.

Needless to say, my messed up sporadic heating in the really cold weather had to do with air pockets, not the aluminum core.

94 Civic Si

What was the problem hose?

TomCat39

The small hose from the heat core control valve to the heater core on the engine firewall side. Part #4

Thankfully for me, my parts car had this hose in the silicone upgrade. It's the one hose I didn't take from it until now.

Just got done swapping the hose, filling the coolant back up and burping her. No bubbles in the rad, fan kicked on twice, nice heat in the cabin and no over heating so looks like I caught the overheat (thanks to my wife) before more severe damage occurred.

Anyways, I've confirmed my gross error. The slightly smaller all aluminum heater core works just fine even in this grossly cold weather. The only trouble spot for them is they need a little extra padding to fit the box the same as OEM. Other than that, they work just fine for 1/3rd the cost.