Looked under the dash of the Tahoe tonight

[Camino LS6]

Thanks, it does look pretty good.

[A Horse With No Name]

I just hope it works out for you. I'm probably going to be keeping the Miata for a rather long period of time....and watching other people keep older vehicles on the road is encouraging.

[Camino LS6]

Well at 15 years old and over 185K miles, this truck is better now than many a sub-100k car I remember from the past.

But, the electronics could prove to be a real achilles heel as time passes.

[A Horse With No Name]

OBD II is kind of scary when you think about CPU's going bad over time....

[SAmadei]

OBD II is kind of scary when you think about CPU's going bad over time....

I've got 20~25 year old CPUs that still work. Its usually capacitors... which can be replaced easier than other components.

PCMs so far haven't demonstrated massive age-related failure. Sure, plenty die or get flaky, so its something to wonder about 40, 50 years from now.

[Camino LS6]

This has certainly turned into quite the saga - and it's not over yet.

Ever since I ordered the new blower motor, it has been working just fine - figures. I picked it up anyway, along with a new thermostat.

I decided to flush the heater core again, it flows quite well.

Still not getting hot enough.

Has me a bit puzzled to be honest.

So, I decided to check the intake manifold bolts. Quite a few few of them were very loose - so there is my coolant leak. I tightened all of the ones I could easily reach.

For now, I think I'll put some miles on it and see what happens.

[Blake Noble]

Your Tahoe has the exact same issue my dad's old '99 Dakota had: no heat. He changed all of the freeze-out plugs in that truck (5 of them had small holes tapped into them), flushed the heater core (a massive wad of black crap came out), and then had someone take the dash completely apart to find out something (I can't remember what it was for the life of me now) was simply unhooked/had worked its way loose.

[Camino LS6]

That had to have been the blend door (its actuator unplugged?).

I do have a new theory about the Tahoe's current issue.

The fact that my fan now seems to be working just fine is making me wonder if debris got in there that now might be jamming the blend door in an open position.

All of the stuff I've done so far was needed, but there is still another problem that I haven't positively identified yet.

Time to rip out the old fan and have a look, I guess.

[A Horse With No Name]

Think electrical first and airflow next...your solving this like a commercial A/C-refrigeration guy....

You sure your really a landscaper?

[Camino LS6]

I've been many things...

Thanks for the compliment though.

It's all in good fun, as long as it works properly before the real cold hits.

I now know the dash of the Tahoe in much greater detail than I ever intended.

[A Horse With No Name]

That's okay, part of the fun of fixing things is learning new things. I've learned a lot of things I never thought I would...or never needed again, for that matter!

[Camino LS6]

True.

This will all be useless when I dive into the HVAC on the wagon.

Totally different systems.

[A Horse With No Name]

If you keep the original A/C components on the wagon, R-409-A will work in place of R-12....but you didn't hear that from me....

[Camino LS6]

Noted!

[A Horse With No Name]

We might be able to arrange a little "fill up" if the wagon wandered westward...

[Camino LS6]

I will keep that in mind, sir.

[Drew Dowdell]

There might be a Toronado wandering westward in the Spring, just a tad low on R-12

[Camino LS6]

Today was not a good day in Tahoeland.

[Camino LS6]

OK, so yesterday was an exercise in frustration - mostly due to the insane location of the actuator for the air door that directs air either from outside or inside the cabin.

Long story short, out came the glovebox, the ECM, the heater core cover, the old fan, the overflow tank for the cooling system, almost the housing around the fan (it CANNOT be removed without dismantling the netire system)...

And then,

Finally,

The actuator.

I confirmed that it was indeed non-functional, and set about getting a new one.

Had to drive about an hour round trip to the only Chevy place that had one in stock.

Plugged it in.

Inop!

So, I made one out of two and made it work.

Today, I began re-assembly.

Only to discover that my new NAPA blower motor does not fit.

Since it has been working, I re-installed the old one.

Actuator now works fine.

But...

Still no heat to speak of.

Only two things left to do.

1) install my new thermostat. Which needs to be done anyway, but is unlikely to solve the problem.

2) replace the "new" heater core. I suspect that the Dexcool crud has plugged the fine passages internally, even though the flow through the unit is fine.

I want to know for sure, so I will do the thermostat tonight and re-test.

Most likely I'll be replacing the heater core tomorrow if I can find one on a Sunday.

[Drew Dowdell]

You can flush just the heater core directly.

Disconnect the ends of the heater hose as far away from the core as possible.

Run the "in" hose to the ground.

Attach your garden hose to the "out" hose.

Turn on spigot.

Essentially, you'd be running fluid through in reverse and would help to de-gunk the core.

[Camino LS6]

I've already done that repeatedly.

[Camino LS6]

I just finished replacing the thermostat (no change noted).

So I think I'll take it for a cruise to the local Pep Boys.

If it doesn't heat up in that time, I'll see if they have a heater core in stock.

[Drew Dowdell]

When you've done that repeatedly, does water flow through the core?

[Camino LS6]

When you've done that repeatedly, does water flow through the core?

Yes, quite well in fact.

I think that all of the small passages are clogged and the water is just running through rather than heating the core.

It really is the only variable left.

Didn't get hot on my trip to Pep Boys, and the core was out of stock.

Oh well.

[A Horse With No Name]

There might be a Toronado wandering westward in the Spring, just a tad low on R-12

We might be able to work something out....

[A Horse With No Name]

Yes, quite well in fact.

I think that all of the small passages are clogged and the water is just running through rather than heating the core.

It really is the only variable left.

Didn't get hot on my trip to Pep Boys, and the core was out of stock.

Oh well.

I've had horrible luck buying anything from Pep boys, and avoid them like the black plague.

As for the heater core, you could try getting some commercial grade Ice Machine cleaner or some commercial grade evaporator coil cleaner and running it through the coil. Essentially both are a mild acid that will eat away sediments and deposits. Your other trick? They make a solution for dishwashers that is a form of acid that is nickel safe and aluminium safe, but will remove calcium build up and sediment like there is no tomorrow.

The coil cleaning solution you would have to buy from a wholesale type of supply house...but several of those sell to the general public as well. You also could set up a cash "business account" in your business name and buy over the counter.

The dishwasher stuff is available from Lowes, at least around here. It takes hot (120 degrees plus) water to activate, but that shouldn't be any problem. For under ten bucks you can buy either 3/8" or 1/4" plastic line from Lowes or a plumbing supply dealer and an adapter to hook up to a sink. From there it's hot water and you are off to the races.

My other Mustang was a Fox body, and it had a heater core that was an absolute utter pain in the arse to get to and change. I wouldn't wish that project, even on loki....

(Just kidding loki...)

Can't imagine what it's like in the Tahoe, but it can't be good.

[Camino LS6]

Actually, it's easy.

And cheap.

Nothing compared to getting at that actuator!

I think I could do the job in less than an hour (if I had the part).

Has to be the most accessible heater core I've ever seen, has its own access panel all the way at the bottom of dash at the floor.

[A Horse With No Name]

Then by all means replace the core!

I was thinking it would be a four hour PITA job to get through....

[Camino LS6]

They usually are.

This one is in a most logical spot.

The actuator was the big PITA of this whole affair.

My only worry is that the damn core flows water so well that I am doubting myself a bit. But I can't think of much else that could be keeping me from heat at this point.

[A Horse With No Name]

How about the water pump? I've known older water pumps that don't flow well....just banging my head.

Also, are you sure the hoses are in good shape? Grasping for straws here.

BTW...saw a Green 3rd gen corvette, T top Coupe, L48 automatic, matching green interior, maybe a 74 or 75. Later style (think 78 Indy Pace car Replica) Corvette rally wheels. Parked next to my work truck when I was running a service call the other day.

Thought of you and another green third gen.

[Camino LS6]

That C3 is still in play - I'll post if/when anything happens.

The water pump seems to be working just fine - truck runs nice and cool, no noises or leaks from the pump.

No collapsed hoses - all look good visually.

The core sits at an odd angle though, I'm going to loosen its mountings in the morning and drop it to a flatter position just to rule out air pockets. But it is already lower than the rest of the cooling system (except the very bottom of the radiator).

It's a stumper.

Edited October 24, 2010 by Camino LS6

[A Horse With No Name]

...a stumper...for me too....

A pocket digital thermometer would tell you what the core is temping at, and might gt you useful information on how much of an actual water flow issue you've got....

[Camino LS6]

Couple things I forgot to mention:

- There was debris in the ductwork that had passed through the fan and lodged against the A/C evaporator, the shop vac took care of that.

- And, the Tahoe is running better than ever after tightening the intake manifold bolts.

More power, better idle, hopefully improved mileage. I'll get to the bolts I couldn't easily reach after the HVAC issues are solved.

[Camino LS6]

...a stumper...for me too....

A pocket digital thermometer would tell you what the core is temping at, and might gt you useful information on how much of an actual water flow issue you've got....

I can see and touch the entire core - it has a few warmish spots, but no hot ones.

Yet flows water like crazy when I put the hose to it - didn't even notice any crud coming out during the flushings.

Edited October 24, 2010 by Camino LS6

[A Horse With No Name]

Assuming that the water temp is where it is supposed to be, it is not transferring heat. The smaller passages probably SLOW DOWN the water enough to release heat into the cabin of the Tahoe. That MIGHT be where the problem lies.

[Camino LS6]

That's what I've been thinking - but it seems so odd.

[A Horse With No Name]

Heat has to transfer somehow....if the water passes through too rapidly, of there is sediment keeping it from contacting the inside of the core....THat would do it.

Which is why I was so concerned that the inside of the core was actually clean....

[Camino LS6]

Exactly, that's why I think the small passages are plugged.

I'm not tired, and it's only one fastener, so I think I'll try to "burp" the core right now - then go get a snack and see what happens.

[A Horse With No Name]

Exactly, that's why I think the small passages are plugged.

I'm not tired, and it's only one fastener, so I think I'll try to "burp" the core right now - then go get a snack and see what happens.

Good luck.....

[Camino LS6]

Well I'll be damned, it worked.

I have heat.

[A Horse With No Name]

Just in time.....

[Camino LS6]

Yup.

I may take a pic of the heater core after i secure it in place again - you'll see why the air got trapped int there.

[Camino LS6]

Thanks for being sounding boards for me during this repair, guys - it is much appreciated.

Now for some sleep!

[A Horse With No Name]

Heading off to bed myself...a sleeping cat and cuddling wife await....

[Drew Dowdell]

I didn't think it'd be the core if was was flowing through it like you said. Even a dirty core, as long as the water can move, should get some heat.

[A Horse With No Name]

Depends on what you mean by some..moderately warm coil + lots of airflow + cold air at the vents. Just not enough BTU's to provide a noticeable change in temp.

I've seen several cars do this, mostly big V8 cars driven at low speeds where not a lot of heat builds up in the winter. Which is one thing I've always liked about smaller 4 cyl cars as winter commuters. They build heat in the motor much quicker, and then heat up much quicker.

Unless it is an air cooled VW bug, in which case you have heat about the time you hit the city limits of Miami, Florida...and then you have no A/C.

[Drew Dowdell]

Depends on what you mean by some..moderately warm coil + lots of airflow + cold air at the vents. Just not enough BTU's to provide a noticeable change in temp.

I've seen several cars do this, mostly big V8 cars driven at low speeds where not a lot of heat builds up in the winter. Which is one thing I've always liked about smaller 4 cyl cars as winter commuters. They build heat in the motor much quicker, and then heat up much quicker.

Unless it is an air cooled VW bug, in which case you have heat about the time you hit the city limits of Miami, Florida...and then you have no A/C.

Well, we're not talking about old muscle cars in the dead of winter here. It's been in the 50s or 60s around here (and Camino's weather is about 12 hours behind ours) with a fairly modern HVAC system. If it was flowing water the way he said it was flowing water, he should have been getting some heat.

If there is something I do better than anything else, it's thinking through trouble shooting. It's why I get paid to sit at work and surf C&G all day.... because when work has a problem with the systems, they know that I can hunt it down and identify the problem faster than anyone else.

[A Horse With No Name]

Logically yes....

[Camino LS6]

Well, the problem was the core - just not the same problem initially thought.

This poor Tahoe had so many problems within this single system that correcting them was bound to be a drawn-out affair.

I have to tell you, I feel pretty good about conquering it.

But I still have a laundry list of other things to fix,

This truck will keep me busy for some time yet.

For now, I have heat and my interior is back together at last.

[A Horse With No Name]

Glad to see you make progress....