Fellow Forum Goers,

Recently bought a '93 FD and it has no working heat. Since it is getting chilly out, I would like to remedy this issue.

Up front, the AC works, almost too well, blowers work fine (understanding that heat does not come out of the face vents), fuses appear to be functioning properly (have not pulled apart dash to check the unit connections or resistors, just no heat. Upon further inspection I believe one of the previous owners bypassed the heater core completely with the coolant lines (see picture 1 and 2 for reference) as they are cut coming out of the firewall.

Reason I am asking is I haven't found the best layout diagram in the Service Manuals to pinpoint the exact hose location and routing for the heater core. Photo #3 shows a screen shot from the parts catalog manual, Page 3-D4 with the layout of the heater hoses and Photo #4 is a screenshot from the parts manual showing the heater core unit inside the dash. Would like to flush the heater core as a start, but need to make sure everything is installed properly.

Curious if I need to purchase the inlet and outlet heater core hoses (photo #5) from Atkins Rotary into the coolant lines, or if additional work is needed. Previous owners paperwork mentioned from a random shop about replacing the heater core with very little explanation, but I will cross that bridge if it is needed once everything is hooked back up properly.

Any help or insight is greatly appreciated, thank you for the time. I can take additional photos if needed for reference as well.

Cheers,

-milly


Photo #1

Photo #2

Photo 3

Photo 4

Photo 5

 

Not sure if you're expecting the hoses to fix a no heat problem. They won't, but it's a good idea to replace them.

Take off the blend door actuator cover under the passenger footwell and see if the actuator moves full sweep with the hot/cold switch.

 

yea, in the pictures you can see your heater lines are cut. the video details what you need to do to start to fix it. its possible that the heater core is leaking and the decision was made to bypass it instead of fix it. its not super common but it is something that happens on the FD

 

Alex. Thanks for the response. Nope just wanted to make sure everything was hooked up properly before I go down the heater core and actuator rabbit holes.

Rex,

Thanks for the video, explains everything perfectly. I’ve seen write ups how you should have only OEM hoses for the coolant lines on the FD, but I can’t imagine in 2019 that quality hoses from the local store shouldn’t suffice. Has your experience swayed one way or another?

Thanks

 

Parts store hoses will leave you on the side of the road for sure. The OEM hoses are really good, they updated the material at some point and getting 100,000+ miles is well within reason. They can take the heat and pressure no problem.

I'm also thinking that they may have bypassed the heater core if it was leaking. Replacing the heater core is a big job, the whole dash needs to come out.

Stock, the coolant goes from the rear driver's side of the block up to a metal pipe along the firewall. Then, from the pipe to the top nipple on the heater core. Bottom nipple of heater core goes to a metal pipe that runs along the passenger frame rail then goes from the pipe to the lower part of the water pump housing near where the lower radiator hose connects.

Also, if the car is single turbo I've seen people remove the metal pipe on the passenger frame rail since the turbo hits it.

All the hoses are relatively short. 4 hoses in all. If possible get the OEM spring clamps, they work better and are nicer on the hoses than worm drive clamps.

Dale

 

Dale,

Thanks for the reply. OEM hoses it is...I believe Atkins Rotary has them so I'll drop an order in. Yes, I am starting to assume the heater core is probably shot, but the dash is going to come out this winter regardless for some maintenance, might as well tackle the heater core while I am at it.

Thanks again.

-milly

 

its hit or miss with the parts store stuff. there is some good heater hose out there but it gets kind of expensive per foot in this diameter. gates should have something and then if you put a nice heat sheath or something over it, it will last for many many many years. thats my experience. its what i did on my old gt35r set up. oem is always the best of course if you have the factory hard lines in place.

 

I hate to bump an old thread, but my question seemed relevant to this thread's topic. Picture shows the heater hose connection on the driver's (left) side of the block. My question is, should the hose be pushed on and over the nub on the pipe (red arrow pointing at the nub), basically hose pushed all the way on to the iron? Or should it just be pushed up against the nub? It seems like the hose should be pushed over the nub and then the clamp positioned on the hose between the nub and the block. Mine is currently just up to the nub, not over it, so seems like a coolant dump waiting to happen.

 

Your intuition is correct. Move the hose clamp, push on the hose to the block and reposition the clamp between the nub anf the block.

 

Thanks for confirming.

 

Negative.... the hose does not go directly onto that pipe. There is an adapter piece that goes on there and the hose goes on THAT

https://www.atkinsrotary.com/93-95-R...5-61-240A.html

 

^I was about to say the same thing. You can also buy the same Mazda part # referenced above from Ray Crowe and probably get it for less $ and sooner.

 

Thanks for the corrections. My car does NOT have the adapter. Order placed to correct that.

 

My apologies for the bad information. I never saw anything like that before. Hopefully the stock size hose was used, otherwise, it may not fit over the adapter.

 

No problem. It's currently parked in my garage anyway.

The hose I have is molded and fits the hardline that runs across the firewall perfectly. So I'm pretty sure it's the OEM part.

 

Ok, good to know. Now that I look closer, the part is a reducer. The person that installed the hose probably wondered why the OEM hose seemed so small. They just gave up and put it on the end. This could have ended with a popped hose or worse. Nice work finding the mistake. And thanks to @FDAUTO !

 

Full disclosure, the popped hose is how I found it. Just glad it happened a mile from my house instead of 2 days earlier during my drive back from South Carolina. Keeping my fingers crossed I got it shut down fast enough to avoid any other damage.