sorry if this has already been covered in the forums but i've been searching for hours and couldnt find anything. heres my issues:
i have no heat. air blows from the dash and the floor but it doesnt get hot at all. i went to the hobby shop on base today and the first thing i checked was the blend door. it worked. the next thing i checked was the coolant and it was low and there was a lot of rust inside. so one of the guys who worked there told me to turn on the car and top off the radiator. after a couple of minutes of idling i noticed that the radiator was spilling out coolant. he saw steam coming out but thought it might be emissions so we tested the air with one of those things that sucks in air and the liquid inside changes color if hydrocarbons are present. everything was fine(thank god). so by the presence of the rust we then took of the hose going to the radiator and examined the thermostat and it was stuck. i replaced that which solved the whole gushing coolant issue with the cap off. but i still have no heat. could the heater core be clogged with some rust????? also how do i go about flushing out as much of the rust as possible??? any help will be greatly appreciated!!!!

sorry, forgot!!!
1992 fleetwood. with a 4.9

Maybe that "rust" is the coolant sealant tabs that is recommended in Cadillacs. Try feeling the hoses going to the heater core to see if they are warm.

Get 10 gallons of distilled water from the local grocery (it's usually sold in 2.5 or 5 gal containers). Get a jar of Prestone flush treatment. Get a package of the Stop Leak brown powder tablets (about the diameter of a quarter, but half inch thick).

Completely drain your radiator, and follow the directions on the prestone flush bottle for the flush cycle. Use the distilled water, and make sure your heater valve is open and running on full heat.

After the flush cycle is done, disconnect the heater hoses. Get a garden hose and GENTLY release water into the heater hose until it comes out clear on the other side, then repeat for the other side. Go back and forth until you don't get any goop out of your heater core.

Drain the cleaning solution out of your system and run a plain distilled water rinse cycle.

Drain the rinse, then change the thermostat and refill with correct coolant. Add three of the tablets. Cycle the engine until the air is gone and you're done.

thanks!!!!! i appreciate all the help. right now i don't have any of those brown tablets in the coolant. i dont plan doing any hard core driving. just a couple of miles everyday until the hobby shop opens back up on thursday. should i just keep her parked or is it alright. also does anybody have any pics where to find the to/from hoses for the heater core. or even a very good description of where to find them.

What's wrong with the hoses to the heater core?

Instead of tablets you can buy Bar's Leaks Golden Seal powder in tubes. $1.44 at Wal-Mart. You need two of them. It's the same stuff made by the same company which makes the tabletts.

theres nothing wrong with the heater hoses. or at least i hope. i just wanted to know where they were so i can flush the core. lets say the core is clogged. how much of a PITA is it to get it out???

theres nothing wrong with the heater hoses. or at least i hope. i just wanted to know where they were so i can flush the core. lets say the core is clogged. how much of a PITA is it to get it out???
The red arrows show the heater hoses which go through the firewall to the heater core. You can disconnect the upper one from the heater valve (plastic T) and the lower one close to the arrow. Flushing AND backflushing is easy, but my heater core started leaking after the procedure... Had to replace with all metall one for $30. It's is doable, but yes it is PITA.

If you look to the back corner of the engine bay on the passenger side you will see a junction of 3 hoses, one comes from the engine and into a fiting, one leaves the fitting and goes straight down, the other goes toward the pass side. disconnect the 2 that exit the fitting and flush those.When I did mine I had to use a air compressor to blow the junk out since a garden hose wasnt cutting it.

I still have no heat though. Replaced my tstat, flushed heater core and radiator and filled with new coolant/water and tabs.

I heard vinegar is a good flush solution aswell.

The air output i get is same as ambient temp which is real cold. Guess maybe the blend door is my problem.

If the heater core inlet and outlet hoses are hot to the touch then there is a good chance that the hearer core is also hot (and working properly). If you still get no heat in the car then it must be somethign else (like the blend door).

Peteski

Like behind-bars mentioned, check (or just replace the T-stat) I also had no heat and would lose coolant when I turned the heat on. Could not figure out or find the leak till I was going down the interstate and smelled coolant shortly followed by the overheat light and massive amounts of steam from under the hood. The T-stat broke in half, it was a micro tear that, I guess doesn't show leakage till the RPM's where turned up. Anyho, 30$ (can only find at dealer) it was fixed. I no longer lose coolant and the heat works just fine.

Well my issue continues.

Things Ive done...


-Flushed the radiator
-Flushed the heater core and blew the blockage out with an air compressor
-Replaced the T-Stat with a195 degree one, Plus new gasket
-Checked the blend door, it changes directions fully when going from 60 to 90 on the climate control
-Used new 50/50 coolant mix to refill
-Replaced the T-Fitting with the proper one with restrictor properly oriented

No apparent leaks in the engine bay or cabin. But when i set it at 90 It still blows cold air out and never heats the car up inside at all

What am I missing? Fuses maybe?

put your hand on the heater hoses and see if they get warm

did you have the heat on full hot when you flushed the core? you'd be better off with water instead of air btw.

put your hand on the heater hoses and see if they get warm

did you have the heat on full hot when you flushed the core? you'd be better off with water instead of air btw.

On the 20 minute drive to school today I set it at 90 and still never blew warm air, when i got to school the air at the floor wasnt cold, but not hot by any means. The coolant temp was in the 93-95 range after 20 mins of driving.

I checked the hoses once I parked. All 3 were about the same temp which was pretty hot, none were noticeably colder then the others.

I did flush with some water, but it wasn't strong enough. The coolant had been neglected by the previous owner and the core was pretty blocked up. If i put water in one hose it never came out the other, just backed up out the hose i put it in. To fix that I blew into each hose and the old coolant and a bunch of debris came out the other hose. It took alot of air to blow it clean, then i flushed with water.

If I had to guess I would think the core may be bad, But it doesn't leak inside the car and all 3 hoses at the T are hot, so I am in no hurry to pull it out and replace it unless I can rule out everything else.

Any other things I can test?

Heater control valve probably

If all three hoses are the same temperature, it means no heat was taken from the heater core. The core has plastic side tanks. Two fittings are attached to the same side tank. Probably the coolant takes a shortcut through that side tank.

It's not that hard to replace the heater core btw. It's a two-hour job for a trained mechanic and a four-hour job for joe shadetree. Mine blew out a little while ago and I found a good writeup in the FWD forum with a search, although I've lost it since (I had the mechanic do it).

If all three hoses are the same temperature, it means no heat was taken from the heater core. The core has plastic side tanks. Two fittings are attached to the same side tank. Probably the coolant takes a shortcut through that side tank.

Ok, so they shouldnt be the same temp. Makes sense, Guess my heater core is probably bad, just not leaking. Do you think its repairable if its shortcutting (could it just be another blockage) or should I just take it out and replace it.If I go the replacement route i guess i will try and save all the cooolant I can since its new.

Thanks for the help

I have a FSM for a 4100 engine so I may look at it if i cna find it fora adiagnostic prrocedure and instructions on how to replace the core, if i cant find it in a search.

I just had my heater core bypassed today. You can wear a warm coat while driving and hope the groundhog saw his shadow . Much easier & cheaper than replacing (save your $ for next repair).

I just had my heater core bypassed today. You can wear a warm coat while driving and hope the groundhog saw his shadow . Much easier & cheaper than replacing (save your $ for next repair).


Well if the groundhog saw its shadow it means summer is on the way here in Texas, Which brings us to the next issue, My A/C doesnt work :lildevil: Thats a story for another thread though, But luckily I know solution to that one already

Ok, so they shouldnt be the same temp. Makes sense, Guess my heater core is probably bad, just not leaking. Do you think its repairable if its shortcutting (could it just be another blockage) or should I just take it out and replace it.If I go the replacement route i guess i will try and save all the cooolant I can since its new.

Thanks for the help

I have a FSM for a 4100 engine so I may look at it if i cna find it fora adiagnostic prrocedure and instructions on how to replace the core, if i cant find it in a search.
Yeah...I would just replace it with aftermarket core. I got mine for $30, all metal. After flushing my core it started leaking from the gasket between a side tank and the core... Replacing the heater core is not very fun. Too less room. Pay attention HOW you remove stuff from under the dash to put it back in the SAME way just in reverse.