My 1988 LFX F40 build. (Page 39/68)
msweldon JUN 28, 08:48 PM
Looks like you have it attached to the heater return line.

Pipes from left to right on the tstat housing are : radiator return, heater return, coolant over flow/fill, then heater feed.

As far as the heater line I'm looking at running it either around the back side of the engine or under the engine oil pan as a hard line segment in the oem exhaust route as I have too much turbo/collector/catalytic stuff going on above transmission. You should be able to 180deg the heater feed over the transmission.

[This message has been edited by msweldon (edited 06-28-2020).]

RandomTask JUN 28, 10:25 PM
Daryl, I was planning on using a c4 corvette fill.

I ran into another issue the other day and between being super busy with life and demotivating. Belt is a bit close, will need to adjust the mounts to get the engine up at least a half inch.

Daryl M JUN 28, 11:15 PM
Msweldon, where did you get that info? I'm a bit confused because the reservoir hose came off of the second or fourth from the left. I know this because when I took the reservoir off of the donor car (Impala), I left the original hose attached. The 3rd barb from the left is too small to fit the original hose. Do you think various car models could be different from one another?
Joseph Upson JUN 29, 11:42 AM

quote
Originally posted by Daryl M:

Msweldon, where did you get that info? I'm a bit confused because the reservoir hose came off of the second or fourth from the left. I know this because when I took the reservoir off of the donor car (Impala), I left the original hose attached. The 3rd barb from the left is too small to fit the original hose. Do you think various car models could be different from one another?



There's a break in the application year at 2013, but it appears to be the result of slight change in the angle of one of the pipes, so probably a clearance modification. Clicking on the pictures in Rockauto, it appears your description is correct sort of. To me it appears the branch off of the outlet neck at the front of the heads is inop until the thermostat is opened. While the stat is closed, it looks as if the coolant is looped through the heater core in order to keep the pump happy and that involves the last two fittings to the right, if you're facing the back of the motor. One fitting bypasses the thermostat from the heater core and the last one to the right feeds the heater core. Looks like the reservoir should link the outlet pipe at the front to the smaller inlet pipe on the left side of the thermostat housing.

https://www.rockauto.com/en.../+water+outlet,10337

[This message has been edited by Joseph Upson (edited 06-29-2020).]

Daryl M JUN 29, 04:07 PM
Joseph , I see how you came to that conclusion, but that doesn't explain why the hose on the reservoir and the barb you think it should go to are different sizes. The bigger barbs are either the one on the right when facing the bell housing end of the engine, or the barb that taps in to the radiator hose barb. I can't tell for sure what side of the pump and thermostat the far right barb connects to.
Joseph Upson JUN 29, 06:43 PM
Looking at the bottom side of the thermostat housing, that's the only way I can see it working. With the stat closed, the only circuit available for circulation are the two fittings on the right side looking from the bellhousing end.

If you look at the bottom of the housing in the pic on rockauto, you can see that the stat is closed and no coolant can enter the block from the branch off of the coolant entry point on the left, and with no flow into the block past the thermostat, you can't get coolant out the front of the heads to circulate anything through the reservoir. When the stat opens, coolant comes in from the radiator on the left and then abundant flow can pass through the heads and out the water neck at the front of the heads, which the reservoir is connected to. I could be missing something since this is an fwd housing, mine is very different and takes a similar but different thermostat.

[This message has been edited by Joseph Upson (edited 06-29-2020).]

msweldon JUN 29, 09:30 PM
As I said.. I needed to double check.. and also stand corrected...

Here's a screen shot right out of the Mitchell online FSM for the LF3

[This message has been edited by msweldon (edited 06-29-2020).]

Daryl M JUN 29, 11:39 PM
Msweldon, you rock. It looks like I can now run my hoses. Thanks.
Will JUL 05, 02:48 PM
The Northstar is similar and pretty much all modern engines have "recirculating" thermostats.

The cold thermostat completely blocks off flow to the radiator. The flow recirculates through the block to ensure that the engine warms up consistently throughout, without any hot spots or cold spots. This ensures the quickest warmup and fastest transition out of cold start enrichment. Once the recirculating coolant is up to temperature, the thermostat starts to open, replacing some of the flow volume of coolant the engine has warmed up with cold coolant from the radiator. This is a gradual process in order not to cool the engine back down. Yes, the coolant circulation pattern is the way it is for emissions reasons.

If you try to use the '87-'88 Fiero heater return (or supply in this case) connection on the right coolant pipe, you will not have heater circulation until the thermostat opens. This sucks on a cold winter day. I swapped my '87 right side coolant pipe and heater pipes for the right side coolant pipe and heater pipes from an '86 and plumbed the heater core to the original connections on the Northstar. Getting heat on a cold winter morning took 1/3 as long as it did using the '87 heater return connection.
Daryl M JUL 06, 01:48 AM
Will, thanks for the explanation. I'm not sure how important it is for the heater to work quickly. I live in Phoenix, Arizona. I can't remember the last time I used a heater here.