Hi fellas. I'm normally on the Corvette Forum with questions for my C4, but I just got another project so here I am.

So I got this 85 TA with a rebuilt and balanced 5.0 TPI motor. It looks like it just rolled off the factory floor, the engine that is. However, it would seem it was rebuilt without any heating components, just A/C, which works fine. I cannot locate the heater control valve (this is how this all started, I wasn't getting heat) and it looks like the water pump outlet at the top has a plug in it where I believe a hose should be. I also did not see any hose running to the firewall for the core.

My guess is the heater core went south and because the car came from FL, they bypassed it. In NY, I need heat for the winter. Does anyone have any pictures of this motor in this year car showing the hose routing, etc.? My FSM is on order and I havent received it yet. I know there are some molded hoses needed, but I need to see which ones. I was able to make my own in an 87 Firebird with the 2.8 using tubing and hoses and I'm hoping to do the same here.

I'm definitely swapping the old core with a new one, that job was a PITA in the 2.8 I had, but doable. I would appreciate any suggestions and tips.

Thanks!

 

The later model Birds had the return for the heat going directly into the radiator instead of into the water pump. You can route it either way. But you should have a hose coming off the manifold into the heater core. Then you should have a hose running either into the water pump for a return or into the radiator. Either way will work. If you have the original v belt set up, I believe it is correct to go into the water pump.
As far as the heater control valve, it is a toss up whether it had it or not. I have 2 birds without it, although I do not have a TPI car.

Edit - I did a bit of research and it seems that the manifold feeds the throttle body, which then feeds a diverter valve that feeds the heater core, or returns back to the water pump or radiator.

 

Thanks for the insight. My C4 with TPI has the traditional SBC heater set-up with hoses from the manifold and water pump. Being this was a similar motor, I expected the same.

There is a large hose that goes into the radiator which I found odd. I traced it to the engine, however as I was still wearing my suit from work, I didn't dive into it for fear of getting my favorite suit stained. I will check again tomorrow during the day for the other hose to the core.

This all started because there was no heat coming out. I let the car idle for 5 minutes and nada. The upper radiator hose was cold though after I shut the car off and so were the valve covers, I expected them to be at least warm, evem tho it was only 35 degrees out. My C4 would be hot after 5 minutes of idling, it uses a 180 thermostat, so I'm using that as a reference. I suspected this car does not have a thermostat installed, which would explain the cold hose. When I started to poke around, I noticed the shiney new plug at the top of the water pump and suspected the heater core was bypassed. You've given me hope my friend. Thanks!

 

UPDATE

So I poked around a bit and low and behold, the heater core is there, but not connected. There is a hose coming from the radiator into the throttle body to bypass it. I spoke to the previous owner and he confirmed the car went thru 2 heater cores in its life. The one that's in there now should be good, it was bypassed when the engine was rebuilt because in FL they never needed the heat. Being the core has been sitting since 2009 "empty", I'm going to replace it.

I can't find a listing for a heater control or diverter valve, so I guess none is needed. However, the diagrams I've seen that show the proper hose routing do show one in place. If the car did have one, where does the vacuum line originate? I figure I'll start by tracing that to see if one is needed or not.

 

Vacuum line probably originates inside the car at the heater controls. There is a little valve behind it with a bunch of plastic vacuum lines attached to it that controls the HVAC system. It should come from that.

 

Thanks, I'll have to look for it. It should be a hard plastic line, correct? I remember those being color coded in the older GM cars.

 

Hope this helps

 

That's exactly what needed. Thanks

 

Apart from the diagram:

The heater core needs 2 connections; a source of hot water, and a return to the cool side of the cooling system.

The source of hot water is the intake manifold, which is where the heated water is collected as it exits the engine to be sent to the radiator, but before it reaches the thermostat.

The return can go into either the fitting on the water pump (which is on the suction side), or to the one on the radiator tank, which is the cold side of the radiator. Those 2 points are essentially the same spot in the system, differing only in that one is at one end of the lower rad hose and the other is at the opposite end.

The factory routing, with that metal line section tucked off to the side out of the way, is obviously the "right" way to plumb it; but depending on how hard your car's PO worked it over, you might have to get a bit more .... "creative".

The vac line should be purple if memory serves; the part out under the hood might just be black though. But it's easy to find regardless: since the HVAC system is an interchangeable option in the car, its entire wiring harness is separate from the car's main wiring. It comes through the dash right below the heater hose fittings. The vac line(s) will be included in that harness. The blower motor and AC compressor wires are the rest of what's in it.

 

The lower pipe is gone. If it was there, I'd know if there was originally a diverter valve from the tee that would be present. I looked at the harness and didn't see any vacuum lines so I think what I've been told holds true, no diverter valve in 85.

I can still get the long feed hose and the return elbow hose on the core from Rock Auto. The rest I'll have to rig. I may get some copper pipe and make the lower pipe. I'm on the lookout for a used pipe from some of the recyclers. The outlet from the core is 3/4, but it reduces to 5/8 for the radiator connection, correct?

 

https://www.thirdgen.org/forums/exte...1986-iroc.html
PM this guy,he comes into a lot of 3rd gens

 

I just pm'd him. Hopefully he has what I need.

Thanks

UPDATE: I just located a NOS part and bought it. Now, I just need the hoses and the core which the local Pep Boys has in stock.

 

Glad you found it,Good Luck.
just a heads up,hose no.1 on the diagram,is a PITA.

 

No...

The hot side is all 5/8", the cool side is all ¾". (whether the pump or the radiator connection is used)

 

That's what I thought, but there is one hose from the radiator to the throttle body bypassing the core. It looked to be one size but I will take a closer look. Maybe there is a reducer inserted where I can't see it joining two hoses together. It's the least of my worries, getting the new core in is at the top of the list.

 

Don't even bother hooking the TB coolant stuff back up. Just hook the heater to its supply and return and be done with it.