Lower Rad Hose Cold

[WES_393]

I just got my TSi up and running and I'm in the midst of working out some bugs. One of which is the cooling system. The water pump has 1K miles, engine and head were hot tanked and scrubbed in both the coolant and oil passages, radiator cap is brand new, and I just replaced the thermostat today. Yet after a quick cruise around the block, the fans are on, the upper rad hose is blaring hot, even the thermostat housing is too hot to touch, yet the lower hose is quite cold. Not ice cold, but nowhere even close to the top hose or T-Stat housing.

My initial thought was junk thermostat. I pulled it out and tested the new one in a pot of hot water. It opens up at around 190* which is a little late, but it still fully opens so I installed it. No change. Next thought was a clogged radiator, but when I had it out of the car it was flushed both ways with a garden hose for a good 20 min at a time. Coolant is about 70/30 if water/coolant and the gauge never reads above half way. Link even tells me it's around 200* at idle. No leaks or bubbles and the system is completely burped. I never even got above 3500rpm since I'm still breaking in the new clutch.

Am I just crazy or does it sound like something in the cooling system isn't working correctly?

 

[jayson427]

thats defintely interesting only thing i can think of is that heat rises and maybe the air flow from the car is cooling the lower hose down and everything else is just hot from the engine bay temps. i dont think its something to look away from but it could just be how your car runs not completely sure tho.

 

[livedsm4g63]

It would be your t-stat. Just keep on eye on it and if starts to overheat try another t-stat.

 

[WES_393]

Jayson- Well that's on the same track as the possibility I'm thinking of. Maybe the radiator is cooling the coolant so well that the lower hose is cold, but that doesn't explain the T-stat housing and upper hose being so dang hot. I'm worried that I might warp the head if I continue to drive the car.

Any objections to trying the car with no T-Stat at all?

 

[jayson427]

i doubt you would warp the head if your only at 200 degrees i live in arizona and my whole engine bay gets super hot i cant touch anything. you should try a lower temp thermostat i have a 160 in my car and it helps big time my temp gauge never goes up to half way. and you could try it without a thermostat and see if your lower hose gets hot but i think you just want peice of mind so i would get a better t-stat and see what happens.

 

[mattasi]

For testing it's ok, but you need to have one installed. I would try a different t-stat.

 

[WES_393]

Okay, I'll pull out the T-Stat and see if that makes a difference. The car isn't daily driven so it will survive without one until I order a Mitsu one.

On a side note, that's just another part that fails right out of the box from Oreilly's.

 

[mattasi]

I am guessing that without the t-stat, your car won't even get up to normal temp. Just so you know.

 

[livedsm4g63]

Yeah you dont want to run the car without one in. It could be bad for the engine.

 

[boost97gst]

Mine idles at 200F, new tstat. And yes, ive noticed the lower hose to be a bit cooler. Not a lot, but somewhat. Pull that tstat and run without one. If its anything like the temps here in stl, youll be fine. Unless its below 70 i would think your car will get up to 180 or so. Sitting at idle itll go all the way up til the fans kick on, tstat or no tstat.

 

[boost97gst]

Yeah you dont want to run the car without one in. It could be bad for the engine.

If its really hot like above 90 would it really drop him that low? Im curious too. Never done it though. Highway travel would be your biggest concern as far as low temps go. You want atleast 180, i wouldnt run it at 150 or less, i too think that would be bad for the engine. The block wouldnt be expanding to normal op temp size, yet the heat from combustion would cause rings to expand like normal. Bad combo. Just make sure your atleast 180 on the freeway. nuff said

 

[96mitsugsx]

Did you bleed the system?

 

[007jimmy]

I would run without the t-stat at idle only to see if the lower hose temperature gets hotter. It would take longer to warm up but i wouldnt advise to drive it that way. If you see a temp change then you probably have a bad out of the box t-stat. Has happened many of times to many of us. Check your rad for cold spots to see if you might have a partial clog. Be sure to unplug your fans if you choose to do so.

 

[WES_393]

I pulled out the T-Stat and gave the engine a whirl. It took a bit longer to warm up as expected, but got right up to 200* and stayed. Both hoses were at pretty equal temps and when turning the fans on with Link I could watch the temps drop. So it's safe to say the T-Stat was bad right out of the box and that the cooling system is very capable of doing it's job. Looks like I'll be ordering a Mitsu T-Stat.

But, now the coolant light is on all the time. I'm thinking the heat messed with the sensor.

 

[007jimmy]

I pulled out the T-Stat and gave the engine a whirl. It took a bit longer to warm up as expected, but got right up to 200* and stayed. Both hoses were at pretty equal temps and when turning the fans on with Link I could watch the temps drop. So it's safe to say the T-Stat was bad right out of the box and that the cooling system is very capable of doing it's job. Looks like I'll be ordering a Mitsu T-Stat.

But, now the coolant light is on all the time. I'm thinking the heat messed with the sensor.

Check the sensor at the bottom of your overflow tank. 95s had a sensor at the bottom of the bottle. Check for proper connection and for corrosion.

 

[EclipsedFLA]

I just finally tore into mine only to find no t-stat.. So i stuck a 170 on, cleaned off the corrosion build up on the sensors and shes below normal operating temp...so far I haven't taken her out in mid afternoon 90+ degree weather though. My lower hose did tend to be colder previously, But I am yet to check it ater the install..
(Still cleaning up previous owners messes)