Should I go ahead and replace my heater core?

[Giraffe]

I have a brand new Motorcraft heater core which I have been holding off on installing because I wanted to wait until I put a new engine in.

That's going to be a while down the road, and it's starting to get cold. I think the original is clogged. I get no heat at all. I had the coolant flushed about three months ago; it still looks pretty clean. What would be the likelihood of gunk from the radiator or engine dislodging and clogging the new core?

The car has a new fan clutch and never comes close to overheating. Even when the temperature was in the high-90's and 100's over the summer.

[Kodachrome Wolf]

If you flushed everything pretty well, I don't think you should worry about anything getting deposited into the heater core. If your coolant was still changing colors then I'd be concerned. I'd put the new heater core in just to take care of it before it starts staying cold. Also, now would be a great time to address the heater hoses if they're starting to look questionable.

I used Gates P/N 19682 (Non-ATC car) for the hose that goes from the water pump back to the heater core and P/N 18708 for the hose that goes from the core to the pipe that runs under the intake back to the front of the engine. If you have ATC, it should be P/N 19683 for water pump to the ATC valve, then P/N 19610 from the ATC valve to the heater. The 18708 hose should be the same between the two.

They're both moulded type hoses and keep the engine bay tidier versus running straight heater hose and looping it back in a way to avoid kinking.

[VicCrownVic]

+1
I replaced the heater core in The Ice Car a few years ago after getting tired of it clogging all the time. I also was worried about the new heater core clogging, but a few years later that heater core has yet to clog on me. I had done an engine coolant flush before replacing the heater core, so I'm with KW that if everything was flushed well you should be OK.

Although I seem to recall the state of your coolant when you bought the car was frightening compared to mine, but still I think you should be OK.

(that reminds me, all my pictures in the HC write up are broken thanks to Photobucket. I need to get around to fixing that one of these days...)

[kishy]

A thought: you get no heat, but are you sure it's because the heater core isn't getting hot?

ATC? I would verify the functionality of the electronic blend door actuator right off the bat. If it isn't moving the blend door, your problem may be that instead. You can get eyes on it through the glovebox opening. There's a part that should visibly move when changing the temperature setting with the system turned on in any mode, check this with the fan on a manual speed setting instead of the auto position.

I presume this is for your '90, and that it has the 90+ "E"ATC setup instead of the 89- vacuum ATC setup.

[Giraffe]

If you flushed everything pretty well, I don't think you should worry about anything getting deposited into the heater core. If your coolant was still changing colors then I'd be concerned. I'd put the new heater core in just to take care of it before it starts staying cold. Also, now would be a great time to address the heater hoses if they're starting to look questionable.

I used Gates P/N 19682 (Non-ATC car) for the hose that goes from the water pump back to the heater core and P/N 18708 for the hose that goes from the core to the pipe that runs under the intake back to the front of the engine. If you have ATC, it should be P/N 19683 for water pump to the ATC valve, then P/N 19610 from the ATC valve to the heater. The 18708 hose should be the same between the two.

They're both moulded type hoses and keep the engine bay tidier versus running straight heater hose and looping it back in a way to avoid kinking.

I ran almost thirty gallons of distilled water through it before I gave up and had a shop do it for me. It was still coming out brown even after all that. I replaced the heater hoses last December, so they're good to go. My car doesn't have ATC.

+1
I replaced the heater core in The Ice Car a few years ago after getting tired of it clogging all the time. I also was worried about the new heater core clogging, but a few years later that heater core has yet to clog on me. I had done an engine coolant flush before replacing the heater core, so I'm with KW that if everything was flushed well you should be OK.

Although I seem to recall the state of your coolant when you bought the car was frightening compared to mine, but still I think you should be OK.

(that reminds me, all my pictures in the HC write up are broken thanks to Photobucket. I need to get around to fixing that one of these days...)

The state of my coolant was indeed pretty bad. A whole lot of brown gunk throughout the system. The shop that did the flush after I gave up seems to have done a good job. The fluid in the radiator and overflow look clean, and one of the EGR hoses blew a couple weeks ago out of which everything was also clean looking.

A thought: you get no heat, but are you sure it's because the heater core isn't getting hot?

ATC? I would verify the functionality of the electronic blend door actuator right off the bat. If it isn't moving the blend door, your problem may be that instead. You can get eyes on it through the glovebox opening. There's a part that should visibly move when changing the temperature setting with the system turned on in any mode, check this with the fan on a manual speed setting instead of the auto position.

I presume this is for your '90, and that it has the 90+ "E"ATC setup instead of the 89- vacuum ATC setup.

My doesn't have ATC. When I was attempting to flush it myself, I did get ample heat for a little while before it gradually went cold again. This along with the water still coming out brown after nearly thirty gallons led me to have a shop take care of it.

Thanks, all. I'll go ahead and tackle it soon.

[sxcpotatoes]

You might want to change out your A/C evaporator thing while you're in there, it shares bolts with the heater core and might keep your a/c running longer.

[Giraffe]

You might want to change out your A/C evaporator thing while you're in there, it shares bolts with the heater core and might keep your a/c running longer.

I was thinking about that, too. My AC isn't running right now. There was no pressure at all in the system when I bought the car. I'm planning to replace all the components and get it up and running converted to R-134a before next summer.

I actually removed all the components except the compressor and evaporator. I did notice that the evaporator needs to be removed from inside.

[His Royal Ghostliness]

On the heater core thing, touch the hoses where they hook up to the core, are they both hot? They should be pushing at least 150F after the engine has warmed up properly, if they are cool to the touch or they are lukewarm and you can keep your hand on them for a long while without getting burned that means you have little to no flow thru the core, meaning it's clogged up. Disconnect hoses from core, flush core alone with garden hose in both directions multiple times till you get clean water gushing out good, reconnect hoses and you should have heat then.

If both hoses are nice and hot it means your core is flowing properly, and it's your behind the dash HVAC parts that are to blame - it's not impossible for the blend door cable to have disconnected from the core plenum thus not actuating the door properly. Not very likely, but not impossible either.

[Giraffe]

Thanks for that advice. I checked them today after work and they were definitely cold. I'm going to let it cool off a bit before I do the flush.

[Giraffe]

Hosed it out real good and got some nice heat afterward! A lot of brown stuff was hiding in there.

[His Royal Ghostliness]

Gotta love cheap fixes!

[87gtVIC]

Beats pull the dashboard out of the car.

[Giraffe]

True. I'm going to have to do it anyway when I replace the evaporator. I really didn't want to do it twice.

[BigMerc96]

I discovered long ago that the end of my garden hose sprayer fits nicely into a heater hose. So I've flushed a few heater cores that way. Finally got rid of the water sloshing sound from air in the heater core in my '96 that way. Its amazing how much crap will get trapped in a heater core, especially if the car ever had any antifreeze stop-leak sludge put in it.

[gadget73]

even just never changing the coolant makes it look horrible. I chased sludge in mine for years, even after replacing every single part of the cooling system including the engine. I never managed to get all of it out of everywhere, and the parts were not all changed at once. The remaining crap just re-distributed every time. When I got the car, the cooling system looked like someone had done an upper decker into the radiator. I flushed it daily for 2 weeks, just running straight water in the radiator until it started to get cold.