Hi Everyone! I hope everyone is doing well and safe.
I've been troubleshooting an issue I've been having with no heat getting to the heater core when the thermostat is installed. When the thermostat is off I definitively feel heat.
Specs: 85GT 1998 3800 Series II
Coolant is routed as follows:
Coolant enters at the timing cover port and exits at the modified Fiero thermostat. One of the heater core hose connects just under the snout (under the vacuum port) and the other at the modified thermostat housing.
I have been using Bluedriver Live when driving and see the engine coolant reaching up to 98-99 C (210 F) and operating around 94 to 99 C or 200 to 210 F.
The thermostat installed is a new Delco 195 F. I have tried 2 in total with another replaced last night.
The radiator is an aluminium Champion radiator (thanks Archie) with a new 16PSI Stant 10330. By the way these caps are super sensitive and can seat crooked. Coolant no longer flows into the recovery tank when performing the fill procedure.
I have removed the top hose at the heater core and while filling it coolant started coming out of the core where the hose was removed from so it doesn't appear to be blocked.
The engine operates smooth and I see no evidence of air bubbles. The stock temperature gauge doesn't read correctly but does jump around sometimes ever so slightly. The needle starts at the beginning of the scale and never reaches the middle. Hence why I'm using Bluedriver to monitor the ECT.
I'm stumped on where to go from here short of replacing the heater core which seems to operate without the thermostat installed.
If the thermostat wasn't functioning properly the engine temperature wouldn't be so steady. I've yet to see the engine go above 101 C (214 F) and therefore no overheating issues ever.
Thanks for reading and if you happen to have any insight I would appreciate hearing any thoughts.
The stock 85GT had a nose that came off a nipple on the water pump. On the trunk side of the water pump. It went to a rubber hose that looped around to a metal tube mounted on top of the frame rail. That was the feed for the heater core. Are you utilizing that path to feed your heater?
The stock 85GT had a nose that came off a nipple on the water pump. On the trunk side of the water pump. It went to a rubber hose that looped around to a metal tube mounted on top of the frame rail. That was the feed for the heater core. Are you utilizing that path to feed your heater?
One end is connected on the LIM under the snout and the other off the modified Fiero thermostat housing. The hoses both go directly to the underbody tubes.
On the V6 engine, the hose connection on thermostat housing BELOW thermostat is supply line TO heater core. This way, the heater core gets coolant flow when engine is running regardless of whether thermostat is open or not.
On 85-86 cars RETURN line connected to pipe on Water Pump, pulling coolant through system when engine is running. The 87/88 cars had this line connected to a Tee on the coolant return pipe under the car.
Thanks for sharing this. I can't tell you how many times I've read this post. Unfortunately I'm not using the alternator bracket that came with the engine so my setup is different.
Wait... Have I been the Fiero fool the whole time?
Do I have the wrong port blocked off?? The red circle at the timing cover is currently capped and the yellow circle is where I am utilizing the elbow with a coolant hose clamped to it.
Are you utilizing that path to feed your heater?
I would say no.
Matthew
[This message has been edited by Matthew_Fiero (edited 08-11-2021).]
I'd like to post some more information to maybe clear up the current state of the cooling system.
I am not utilizing the stock alternator bracket with the heater core lines as I have installed a low mount alternator solution utilizing the stock Fiero location.
Matthew, both of the ports you are using for your heater core hoses are pressurized.
The port on the front cover should be used for the heater core return line, and the port below the snout should be plugged.
Thank you. This is the way I had it when I first built the engine. I'll switch it back and report back. My hose is too short now to reach back to the timing cover so I'll have to go purchase another length first.
There is also Plan "C" for the 3800sc. Use the modified Fiero t-stat housing to send water to the heater like you're doing. Dump the heater return water into the passenger side coolant pipe near the rear pass-side wheel well like the 88's. All you need is a Tee in the rubber inlet hose to the water pumps suction side. Less hose clutter at the engine too. Plug the port on the water pump with freeze plug or tap threads and plug it. Same with the one on the manifold. See pics'.
I did mine this way and I have plenty of heat. The last 2 images are respectfully borrowed.
Spoon
------------------ "Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
[This message has been edited by Spoon (edited 08-15-2021).]
