New advice on Inline mod without thermostat. p0126 Code
 

Hey board,

Nice to meet everyone! I'm a new owner of a 2003 Disco based out of California.

Here are some background on the vehicle, 170k with rebuilt top hat engine 50k miles ago, replaced oil pump and gasket. (approx 4-5 years ago)

The previous owner like many performed Inline mod. however, he did it with coolant bypass and did not install a thermostat.

When i was in process of purchasing the vehicle, he briefly mentioned that i need to warm up the engine. I didn't think it was too much of a big deal since it's a 20 year old car and i'm in a warm climate and don't expect too much issues. however, the first time i drove the car after purchase, the check engine light pop up with the code P0126, which means Insufficient Coolant Temperature for Stable Operation. I asked the seller about the code, he said, i have to wait till the engine gets to 170 before driving the vehicle without trigging the code because he removed the thermostat. He said, since it's not his daily driver, he never had issue warming up the vehicle.

This is an issue for me because i'm planning on using the vehicle for quick trips around the house, it's ridiculous to have to wait 15mins for the engine to warm up for a 10min trip to avoid triggering the P0126 code. the seller said i should just reinstall the thermostat and that should get rid of this problem. here are some of my questions..

1. Am i damaging the engine not warming up the engine to 170 degrees before driving off?
2. If i reinstall the thermostat, am i able to avoid the P0126 CODE without an engine warm up?
3. How would a thermostat eliminate the P0126 code since the code is trigged below 170 degrees? It usually will take 10 mins of driving for this truck to get up there.
4. any other recommendations to get around this issue?

Thank you so much in advance for all your help!

Install a 180F and see what it does. It should warm the coolant up to 180F before it starts to open vs free flowing coolant that doesn't warm up nearly as quickly. I'm gonna say you probably have SAI which is super touchy with the P0126 code as it has a second coolant sensor mounted on the radiator.

thank you! do you happened to know when(what temp) p0126 is triggered? even with a TSTAT, i can't imagine it will warm up the engine as quick and most likely to trigger another code. i wonder if the issue is the coolant sensor.

I'm not sure whether you're able to read live data via OBDII from the SAI-specific coolant temp sensor (the normal coolant temp sensor is obviously able to be read). I wonder what the parameters for the code are, though. I (and many others) have no issues starting the truck in sub-freezing temperatures and driving off.

My 2000 with same mileage and head gasket done and in-line thermostat implemented also 6 years ago. I removed the bypass hose and discarded the original thermostat then.
Radiator----> pump----> engine----> thermostat----> radiator and no other paths.
I run 82C (180F) thermostat installed in its inline housing in winter to avoid running too cold coolant; NO thermostat installed in its inline housing in summer (I just removed recently)
Had no problems.
Waiting for an engine to warm-up or not will not do any harm.

So im not really damaging the engine by starting and driving off? im never in Sub Zero weather since im based out of san diego... does lower coolant temp affect other part of the performance by the engine? I see the code under pending, until i turn on and off the car for 2-3 times, then the pending code will be a check engine code. if pending code will still be there after i add the Tstat, it just won't become a actual check engine code. thanks for your reply.

No P0126 code either?

@davidpx858 He has a 2000 so it is a bit simpler, 2003/2004 mostly have a system call secondary air that is what is tossing the code. It wants to run at 180 or better, the code will show up because your Disco does not reach normal running temp range in a specifed time frame. The simplest fix as noted is to put a 180 thermostat in.

The ECM will go to a default setting, and your secondary air pump may run longer .

You will not damage the engine but it may run rougher, use more than expected fuel and possibly fail as emissions test as a lot that is based on heat.

that makes sense...in term of "specifed time frame" do you happened to know what's that time frame to get over 180? thank you!

also, what's the best 180 tstat that's available? i heard it's a grey color or something like that.