WOOHOO! Free beer for me. Actually, that's how I get most of my beer, helping friends fix their vehicles! I really don't mind because it only helps me out in the future.

[JOKE]It is always better to experiment on someone elses vehicle than it is on your own[/JOKE]

 

I actually took it to a shop. They could not find any problem with the sensors. So in desperation they replaced my thermostat. I went and picked it up. They said drive it a couple of days and see if it is better. If it isn't they would flush the heater core. They didn't make me pay anything, as they think I will be returning for a heater core flush.

Well, I can do a heater core flush or I'm pretty sure I can. I did undo the hoses to the heater core last week. I actually was going to reverse the hoses, but they were different sizes. I plan on plugging the in-take hose with a bolt, turn the heater on and try to run a strong enough force of water through my garden hose to flush through the heater core. Then top off with a mixture of anti-freeze and water (good water, not tap!).

While doing this, should I go ahead and replace all the hoses? I have 75,000 miles on the Blazer, average about 11,000 per year. These are very comfortable miles. The hoses look pretty good. The radiator was replaced a month ago, so I have really good fluid right now. That is one reason I am thinking of holding off on the hose replacement. On the other hand I am hoping that I won't be back in the fluid area for awhile. Opinions?

Bocomo

 

Last night I drove the Blazer about 40 miles and the heat did not work (probably in the mid-20s). When we got home I pop the hood and felt the hoses at the heater core. The inlet hose was warm and the outlet hose was cool (there was a significant difference in the "feel" temperature).

In order to flush the heater core this is what I plan on doing, is there more that I need to do?

1. Plug the inlet hose.
2. Fit the garden hose to the inlet for the heater core.
3. Undo the out let from the heater core.
4. Start the care and turn the heater on.
5. Turn on the garden hose to flush out the heater core.
6. When satisfied that it is flush hook everything back up.
7. Enjoy the heat.

Bocomo

 

No need to start the vehicle. Just remove the heater hoses from the engine end of them. I believe that one goes to the waterpump and the other goes to the intake manifold... But I could be wrong in that. Just follow them from the firewall forward to where ever they go and disconnect them on that end. Then just stick the garden hose on the return line with the other end into a bucket or onto the ground. This will reverse flush the core. If that doesn't work, or you don't get a decent flow through the core, then mix up a 10:1 solution of water to vinegar and then pour that solution in to the core, plug the hoses and leave it overnight. Flush again in the morning. The vinegar and water will disolve the gunk that has been built up in the core. If this doesn't work, then you'll need to start thinking about pulling the dash apart and replacing the core, something that has been discussed quite a bit lately in other threads.

 

Thanks Kyle, I'll try it that way first. I had heard about vinegar, too. I'll save that for my second attempt.

 

check to see if the outlet hose is the same temperature - if its cooler then the core is ok, if it is the same temp, your core is plugged and the hot water is just bypassing the core.

 

The outlet hose is certainly cooler than the inlet hose at the heater core. I may need to check out more sensors. Or actually try to find them. It has the LT trim so that rather than just a red and blue dial, you use temperature settings. However, I'm sure that is just putting numbers on the dial rather than the fancy red - blue paint job.

Bocomo

 

This is false. If they are close to the same temp, then the core is ok. You'll only really see a temperature drop of around 20-40*F across the core with the fan on full blast. If the return hose is cool, then you are not getting any flow through the heater core and it needs to be flushed out. There is no way to by-pass around the heater core that I know of.

 

at first it kind of gluged a little, came out a little sporatically. Then it shifted to a steady stream. I doubt I got all of what was in the heater core, but the Blazer had heat driving to the parts store.

I still wasn't happy with the temperature adjustments. But I bought a three volume service manual on ebay today. So when that comes in the mail (or if) I will look further into that. Right now full heat is better than no heat, or I'm sure my wife will think that way.

I'll keep you posted on any further advancements. I appreciate all comments and suggestions, with special thanks to Kyle for his efforts.

Bocomo

 

No problem! Glad I could be of service!