Higher Water Temps after M-Tuned Coolant Reroute??
 

Setup:
1996 with about 118k
T25 turbo with intercooler installed - running MS3 Basic
Koyo 37mm Radiator
M-tuned Coolant Reroute
Bottom ducting is installed (modified for the intercooler piping)
50/50 water and coolant mix
Outside temps have been around 75-85.

After installing the turbo I found coolant temps to be around 205-215 (about 215 after WOT) with the stock radiator. Coolant temp is seen using Tunerstudio.
Since I am prepping the car to be tracked next year I decided to install the Koyo 37mm radiator which dropped temps about 5 degrees. Coolant temps would come down quite quickly after a few WOT runs and would stay around 200-210 which seemed okay for the street.
I figured since I'm tracking the car next year I should go with the M-Tuned Coolant Reroute....and here's where my frustration begins.

I jacked the front of the car up, filled the radiator with coolant and then let the car warm up with the cap off. Lots of air bubbles, inside the cabin I have the air on and its blowing warm, radiator is getting hot to the touch and I can feel the rerouted silicone hose getting hot as well filling with coolant...so I'm pretty sure the thermostat is working.
Fans kick on around 205 and the car continues to idle with coolant temps between 205-210. While driving around coolant temps never go below 200 and I can definitely feel the heat coming off the engine. I'm barely going into boost and it goes as high as 215.

Any suggestions? It's running hotter than before and I have not noticed an increase in warm up time as other posters have mentioned after installing a reroute.

If the reroute is more efficient at pulling heat from Cyl 3 and 4 then the water temps would be hotter....
So yes.

More air out of the system would be my guess. I have a CSF radiator and can run 220hp full pulls at 90* ambient with no rise in coolant temp. When idling as soon as the fans turn on temp drops 10 degrees in 30 seconds.

Yup, bleed your cooling system

I finally broke down and bought one of the giant funnels that helps you bleed. And my god, I would not do it again without it. I got at least another half gallon of coolant in, if not a full extra gallon.

e. Ew, it replaces my Amazon link with a Walmart link automatically. Not cool at all, @IB Nolan.

Go to Amazon and search for Lisle 24680.

1. Fill coolant system
2. Check for leaks
3. Fill funnel 3/4 full
4. Idle car until t-stat opens. Make sure the funnel stays at least half full the entire time
5. Shut car off, remove funnel, put rad cap on (be careful, hot water is hot)

That's the one!

Thanks I just ordered it from Amazon. Should be here Wednesday - I'll report back hopefully with lower temps.

I get all air out without using the smart funnel.
(I used to have one, but can not get them over here, so there)

Raise the nose, idle with cap off till some bubbles come out, then use a piece of cardboard under the throttle stop to raise the idle to about 2000.
Higher pump rpm forces a ton of bubbles out.
Cycle the fan(s) a couple times, you're done.

Also, on a '96 with 118K miles, I would check the water pump if it is the original one.
I have seen cases where pump vanes were corroded to the point of being useless.

I never had an issue bleeding the system where I needed some fancy tool.

Car cold. Radiator cap off, fill with coolant, start idle/rev until it comes up to temp making the radiator full.

Let cool completely with the cap still off. Fill radiator. Install cap, go for a drive, get it up to temp, pull back in.

Let cool completely. Top off radiator done.

I didn't think I had an issue with it either. Until I tried the funnel.

Having a reroute introduces a lot more space for bubbles in the system. I even move the hose around to get bubbles out.

So I got the funnel and bled the system. I also tried a new thermostat...still the same temps. About 210-220. When you squeeze the reroute hose does it feel like there's some give to it/space for air?

I also replaced the water pump last year so I'm hoping that's not the issue but I am wondering maybe the thing has become too weak to flow the water. This is driving me crazy!

Does it still do it?
Test:

https://www.amazon.com/dp/B00A6AS6LY/

Looks like they reversed it?

Water pump belt is tight? Done a leakdown test?

I'd probably run more like 80/20, but that shouldn't be the problem.

What thermostat did you use?

--Ian

Would you please take pictures of the front of the radiator through the bumper mouth, from above, the back of the radiator, and the reroute itself.

I think I got it figured out. I finally got a chance to switch the thermostat from the 195 that the kit ships with to a 180. Temps have dropped to 198-210 with idle around 205. Ambient is at 60.

Only weird thing is as I warm the car up I'm watching the coolant temp in Tunerstudio go up to 245 (needle on the dash doesn't move passed middle btw). After driving around for 5 minutes it cycles back down to 200, then up to 245 again and then stabilizes between 200-205. Not sure what's going on there but I drove around for an hour and temps seemed normal.

The needle on the dash is a fake gauge, for the most part.

To me it sounds like it's a design flaw with the mtuned reroute. Water in the head reaches 245, but the thermostat is just opening. Once water temps stabilize the thermostat is more reactive.

What thermostat did you replace it with. Turbofan toasted a head because he used a thermostat that was not compatible with the mtuned reroute.

My understanding is that a 1/4" dia bypass hole needs to be drilled in the thermostat plate in lieu of the jiggle piece.

+This, seems to be the consensus when I got the M-Tuned kit, to help alleviate the high initial ECT.

OP: Did you happen to test the 195* T-stat when you removed it? Maybe it failed and stuck shut?

I have a two-step 192 or 195* at the back of the head and it reaches operating temp within minutes and seldom goes over 200 aside from idling in 70* ambient. I replaced the design flaw with another flaw as the heater line is post-thermostat so I am depending on the oil cooler line to circulate prior to opening.