no heat

I have 1998 S-10 Blazer with little heat--have flushed the system-- temp gauge goes to a little below half way--can get some (little) heat when system is set to "floor" or "defrost" but very little from vents --

Air conditioner works fine--Is there a "blend door" that could be the culpret?

Your thermostat could be stuck open.

with the engine warmed up and running, feel the heater hoses where they enter at the firewall, if the hose comming from the top of the engine is warm and the hose going to the water pump is cold you could possibly have air trapped in the heater core

Thanks--both hoses get hot

I seem to have the same problem with my 98. The heat gets somewhat warm, but if you turn on the fan it starts to get luke warm. I my case I think its the thermostat, which sits a little above 1/4. How far below 12 o'clock is the gauge?

about 1 and a half hash marks left of center

There is a blend dorr under the dash next to the heater core. In my case the motor in my 98 was burnt out causing it to be stuck in full heat. this is a costly repair due to the labor hours nvolved in removing the dash.

You sure both heater hoses are hot?

If they are, your blending door could be jammed.

I think I have a similar problem. I have had little heat for the past week or so. I felt the top hose coming off the rad and it is warm. The bottom hose is actually cold to the touch after more than 1/2 hour of operation. Usually when I open the hood there is a fair bit of heat coming from the engine but in the last week there doesn't seem to be much heat at all. Not what you would expect when you pop open the hood. I've never had any repairs to the cooling system since I bought it over a year ago. I also notice the engine fan was louder than normal and staying on all the time. I thought that this might be over cooling the rad? The check engine light came on for 2 days and has since gone out. The water temp gauge seems to be running around the 1/4 mark when it usually runs around the 1/3 mark. Is this just a thermostat issue? I'm scheduling an service appointment in a couple of days. Any guesses?

Cheers

For one, when I was talking about feeling the hoses earlier, I was talking about the hose going to the heater core in the passenger compartment and not the rad hoses.

1.) But in you situation, the top hose is always hot seeing it is the hose returning the heated coolant to the rad for cooling and the lower hose is the hose sending the cooled coolant to the engine.

2.) 30 minutes at idle will not bring the engine completely up to temperature.

3.) If you fan is roaring all the time you are driving, the fan clutch has gone bad. Does the roaring ever stop or does it do it continuously?

4.) Go to AutoZone and have the codes scanned and come back here and tell us what code it is. With a check engine light coming on, you will have a diagnostic code stored in the computer memory, you will have to use a code scanner to check and clear the code which is what they do at Autozone conveniently for free.

5.) If the temperature is always at 1/4 even when driving it around for a while you will definitely have to swap out the thermostat seeing it is stuck open. But then again, the fan being stuck on all the time will overcool the rad which also will cause the same problem. This will affect fuel economy among other things.

The code for the check engine light was PO174 Fuel System Too Lean Bank 2 according to the garage. The light had actually gone out on its own 2 days before I took it to the shop. Costs 70 bucks Canadian up here to get a scan. They don't do that for free.

They put a new thermostat in and there is no difference.

When I am accelerating or going up a hill I have heat, but as soon as I back off the accelerator or come to a stop (red light) there is no heat or very little heat.

The water temp gauge now reads just under the 50% mark after a good run on the highway.

They say the clutch fan "appears" to be locked up all the time. Although they couldn't say for sure. Would this be causing the cool temps out of the heater core? Somehow I doubt it.

Also the fan that blows air into the interior seems to very in speed and flow on its own occaisionally. Sometimes when I select defrost the air flow comes out of the middle section of the dash instead of the top by the front window. Computer problem? My Blazer is messed up. What a money pit.

Cheers

Make sure your blending door for the heater is not stuck.

You will know that the fan clutch is bad seeing it will be roaring all the time. Does your roar?

Also, have you had teh cooling system flushed?

I have seen heater cores that are 3/4 pluged up and put out little heat but just enough so that both heater core hoses are hot.. First thing I would do is make sure the rad and overfill are full of coolant. I have also seen bad rad caps cause low heater output. If they are I would do a BlazerLT special and flush out the heater core. Even if that is not the problem its always a good thing to do.
Any hiss sound from the dash area??
And Just a thought when you have very little heat (temp not air flow) while sitting at a light and then it gets hotter when moving that is a clue that there is a coolant flow problem. A stuck open or to low temp thermostat. Blocked heater core , gunked up rad or this 1 I have seen a lot of and is harder to spot is a water pump where the impeller blades are eaten away causing low coolant flow and it does not always show up with a high temp gauge reading

Yip and as I always say, replace the rad cap with something other than a AC Delco.

The AC Delco rad cap has a fibrous rubber gasket which is really piss poor.

hahaha,
I finally went out and bought a new rad cap last night. My cooling system hasn't had any problems for years, but I returned enough bottles (10 cents in michigan) to get it for free @ Meijers. Wish me luck on this install!

Just a thought, could you have an airlock (air bubble) trapped inside your core you might want to try a flush kit (got mine from prestone) hooks into the heater hose and does away with any chance of air trapped.

It is a pressureized system so airlock does sometime occur, but is more likely just a restricted core.

The internal coolant passageways in a heater core are actually very small and plug easily. Just remember to flush one way and then flush the other way so you truly clean the system.

Also, you might want to pick up a stronger flushing agent seeing the Prestone has been known to be a little weak.

Check for a vacume leak, the vac. hoses are easy to follow from the soft ball size vac. resovour located on the hood. You can also see the vac. hose that enters the firewall witch operates the heater doors, this is the hard shiney one. Also make sure that both heater hoses are hot. These hoses are the small hoses that enter the firewall from the engine to the heater core and not the larger radiator hoses. The heater fan should be on high when feeling the heater core hoses for heat. Also a temp guage reading between 25% to 50% should give you plenty of heat and you should be toasty warm. If one hose is hot and the other is luke warm or cool you probably have air trapped in the core. This is not rocket science.