3800sc slow to warm up (Page 1/2)
2greenfrogs FEB 23, 10:51 AM
I recently traded out my old 84 Duke for an 86 with a 3800sc from an 03 gtp. As the swap was already done idk too much about it. I've got about 5k I've put on it myself and it runs great. My only complaint is how slow it is to warm up. On the highway it takes about 5-10 minutes to get warm, and around town it can take the better part of 15 to get warm. I certainly miss the Duke in this regard as it was always blowing hot within 2 blocks. The thermostat is functioning properly, as is the fan. I can watch the temp build up to about 200 and then instantly drop down to about 180 , telling me the thermostat is functioning normally. Once it gets to temp there's no issue

My question in this: is there any way to get the car to warm up quicker? Is there a certain way to route the heater hoses etc to speed the process?
olejoedad FEB 23, 01:10 PM
It's difficult to answer your question without more information relative to your particular setup.
Forrest FEB 23, 03:38 PM
Your thermostat is missing (the case for my 88 and my 86) or stuck open. They are cheap...snag a new one and slap it in there. I bet that sorts you out.
If its stuck open it will take a LONG time for the car to warm up. I only noticed on my car cuz its been freaking cold in Texas and the heater would only start working when I got where I was going.
Engine does not matter.

[This message has been edited by Forrest (edited 02-23-2022).]

2greenfrogs FEB 23, 08:20 PM
I can see the temp drop from the thermostat when it hits it's temp and it will hold steady around 195 when warmed up. I've never had a thermostat still cycle properly when bad. Throwing a new one in certainly won't hurt though.
Frenchrafe FEB 23, 09:02 PM
As others have pointed out, we need a bit more info on your heater hose routing?
My experience is that the heater should be fed before the rest of the cooling system.
Check for the heater hoses close to the engine being hot way before the thermostat opens.
If not, then there is blockage or the swap was badly finished in this area?
Top heater hose should be close to / fed directly from the water pump.
------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France!
https://youtu.be/c4Cu7_2OgYc
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

[This message has been edited by Frenchrafe (edited 02-23-2022).]

2greenfrogs FEB 23, 10:38 PM
I was thinking bad routing of the plumping as a likely possibility as well. Is there a preferred place that the heater lines are fed from or is there only one option? I know I'm missing a lot of info, and fully intend to check out the routing of them as soon as the snow is done. With temps in the teens I was hoping to find a little direction here, so I could get the most out of my time while I'm freezing lol.

Thanks btw!
Frenchrafe FEB 24, 12:38 AM
My experience with the 3800 shows that you should keep the original heater return line with it's splice into the main coolant return. (Rear right under the car.)
This means blocking the 3800 heater return on the motor with a plug/cap.
Use only the heater output on the engine.
You may have these two inverted; ie the heater is being fed by the wrong one of the two engine pipes/outlets/inlets. (Close to the water pump and/or part of the alloy alternator bracket/belt tensioner.)

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France!
https://youtu.be/c4Cu7_2OgYc
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

2greenfrogs FEB 27, 09:57 PM
French, this might be my issue actually. They've got a mess of hoses and whatnot going on behind the engine.
Larryinkc FEB 28, 08:43 AM

quote
Originally posted by 2greenfrogs:

French, this might be my issue actually. They've got a mess of hoses and whatnot going on behind the engine.



If that doesn't help the thermostat may have been drilled with too large a hole. I put a new thermostat in my 3800 swap and drilled it too large and had the same issue with slow warmup. I think I ended up with a 1/16 hole and warmup is OK now.

https://www.fiero.nl/forum/...090219-2-078414.html
theogre FEB 28, 11:11 AM
Heater loop should be plumb sim as shown in my Cave, Heater
w/o that plumbing can bent the T-stat for OE Fiero T-stat to blow/fail hoses, WP and more.

Most OE type T-stat for many cars will "slam" open and close. worse on cold days or have other problems. Fiero is far worse because 2 - 4 times the amount of coolant to reach operating temp. May never reach that depending on other issues/problems and gauge will swing forever.
Get Stant super T-stat. See my Cave, Thermostat

Many people put "3 core" and other radiator "upgrades" that causes problems like slow to warm up no matter what weather is for a day.
If true, you may never "fix" your problem.

If have used 180°F or worse 160° T-stat will cause same problem. Use 195° T-stat nearly all engines are made for.

And don't trust Dash Gauges. The numbers mean very little.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave