The Lotus Cars Community banner
Cancel

Heater Core Bypass Mod (Tony Wa) [How To]

107037 Views 349 Replies 74 Participants Last post by  kapps, 
Tonywa28
Here's the kit, parts list and instructions

Thanks to Rob (who pointed out the obvious vacuum source, DOH!:wallbang: ), I re-invented the whole thing and it is working great for me. One hour ride yesterday that was nice and cold. Heat comes on very quickly after switching out of bypass mode. Best thing is there are no real custom parts. I have an extensive write-up with pictures, parts lists, cost and diagrams atttached. I would be willing to put some kits together if people are willing to reimburse my time and shipping. Maybe $25 bucks (?) above parts and shipping for running around and packaging. My feelings won't be hurt if no one is interested. I'd like to use the $$ to start working on a short shifter solution (at the transaxle, not the lever).

Now to the disclaimer. This mod works great for me. I can't promise it will work for everyone, but I don't see how it could hurt. Easily reversible if so desired. Use at your own risk....affect on warranty unknown....your mileage may vary....CMA...CYA.....

BTW - I see no difference in indicated coolant temperature with or without the bypass

I think we should get a handful of testers (2 or 3) to check their results before we go wild with this mod. I sent Rob a preliminary document and I think he's working on an install now. Hoepfully he'll post results.

To the poster with 226 degrees. That sounds like a problem with your specific car. I've never seen 200 degrees and almost never see 193 (maybe 2 or 3 times in almost 2 years). Check you fluid levels, check for vacuum leaks. Use may want to try some Red Line Water Wetter (I'm a believer).

Attachments

Reply
Save
Like
341 - 350 of 350 Posts
S
A few reports of coolant leak at the valve because the worm drive hose clamp got loose.
I used 7/8 constant tension hose clamps. hose clamps


The plastic universal vacuum tee I got was too small for the brake booster hose.
A metal 2mm-6mm-12mm Tee 3-Way Brass Tee was perfect.
Vacuum Tee

Pig tail for the EGR solenoid valve

I made an extra control box that controls the EGR solenoid by the flap actuator control voltage, I fixed it behind the wiper motor and it got in the motion path of the wiper arm. The wiper motor got very hot because it was stuck at the wrong place.
Verify your wiring and vacuum lines are not interfering with the wiper before you button up everything.
Reply
Save
Like
cyow5
SheeperS said:
A few reports of coolant leak at the valve because the worm drive hose clamp got loose.
I used 7/8 constant tension hose clamps. hose clamps


The plastic universal vacuum tee I got was too small for the brake booster hose.
A metal 2mm-6mm-12mm Tee 3-Way Brass Tee was perfect.
Vacuum Tee

Pig tail for the EGR solenoid valve

I made an extra control box that controls the EGR solenoid by the flap actuator control voltage, I fixed it behind the wiper motor and it got in the motion path of the wiper arm. The wiper motor got very hot because it was stuck at the wrong place.
Verify your wiring and vacuum lines are not interfering with the wiper before you button up everything.
Click to expand...
It's actually the valve itself that can leak, not just the clamp. I replaced my valve after it developed a leak (and you could see if coming out near the actuator), but I can't remember exactly what the new one is. I haven't put enough miles on it to evaluate reliability anyways. There are some other designs that are electrically operated instead of vacuum, so that's probably the cleaner approach
Reply
Save
Like
E
I used this:

https://www.oldairproducts.com/product/50-1555-heater-valve-kit

Which runs off of the same wiring as the heater flap. Actually bought the correct connector and pins to make a t harness



https://www.lotustalk.com/forums/f313/2007-exige-ac-heater-rework-348738/

less than 4 years so not truly long term as yet...
Reply
Save
Like
S
I noticed the air was still a little warmer than ambient when the bypass valve was activated.
I checked the bypass valve after a drive, and found the 2 hoses to the heater core is a little warm. It is about 110F, so a lot cooler than the 190F circulation hoses.

The valve is the Motorcraft YG350 one.
Anyone else noticed the bypassed side a little warm? The valve's lever is sucked to the bottom when it's activated.
Reply
Save
Like
E
probably not significant if your flapper still works

pretty hard to get my hands in there on the Exige to check

It is pretty hot under there, and the dash in the sun can add a fair amount of heat
Reply
Save
Like
S
From touching the hose clamps of hoses to and from the heat core, I think there is a little bit of hot coolant circulating to the heater core.
Makes me wonder if I got a defective valve, or a little un-diverted flow is expected.
Reply
Save
Like
E
It could be expected, I don't know.
I never closely checked my[different design] valve in service.
Reply
Save
Like
kapps
Quick question about the wiring... the instructions say to ground the black wire and take the other one into the cockpit. I have a generic harness for the VS12 EGR switch with two black wires. I'm not sure if putting in reverse polarity will damage the switch so I figured I'd ask which pin is ground?
1257661
See less See more
Reply
Save
Like
S
In your picture orientation, the right pin gets +12v, and left is gnd.
Reply
Save
Like
kapps
Thanks!
Reply
Save
Like
341 - 350 of 350 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
The Lotus Cars Community
A forum community dedicated to all Lotus owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
General Discussion (Lotus related) Closed/Sold Parts Lotus Elise Lotus Evora Closed/Sold Cars
Top