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Wild coolant temperature swings

Airborne

Just a regular dude
Messages
294
Location
Utah
Ok gents I am scratching my head a little with this one. My coolant temps have been all over the place. I noticed it last spring but have been out of town so many times for work I haven't had the time to address it. It lasted through the winter doing the same thing. I used the dummy gauge on the dash for a while before I plugged into the obdII.

If the ambient temps stayed below 40 F outside I wouldn't go above half. Which was normal for me. Actual scans correlate that to 175-185F. I really noticed it would climb when I would get off the freeway and there was a strong headwind. The coolant temp would start to climb rapidly. Well above half. 190-210 F. Not worrisome to me.

Then after winter temps sarted to go up so did the coolant. Today it really started to worry me. Temps were in the 40s but the temp would still go up to 3/4. Scan says that was 220-235F. 40 degree ambient temp combine with zero long hills and not towing seems pretty hot to me.

I immediately think a sticking thermostat. The radiator is new and burped but that is relative I guess.

I am worried the header may be pumping out a lot of heat into the bay that the coolant system may not be able to handle. The reason I think that is the intake temp is around 110-120 F at idle, which leans me to overall bay temp being high.

I have yet to add an external trans cooler and I'm sure that is contributing to the overal problem to a degree.
I haven't been able to get a reading on the transmission temp but would like to know if anyone knows what system will do that. I have an obdII scanner with the app. I also have HP tuners but the last I remember hp tuners doesn't read the trans temp on these. Which may have changed I haven't used it for a couple years now after I tuned it.
Is there another option for getting a real tranny temp? Also could the transmission heating up really heat the coolant that much and that wildly?
Fluctuating 50 degrees in 5 minutes seems crazy to me and is indicative something or collective things may be happening. Or am I wrong all together and this is normal?
 

Airborne

Just a regular dude
Messages
294
Location
Utah
I know a super long post. Probably should have been a couple different ones. Especially with all the different questions. Thanks in advance guys.
 

JPaul

Well-Known Member
Messages
2,436
Location
Way up north, UT
If you're running a header without heat shielding that might be contributing. If the manufacturer says it's OK I'd put some header wrap on it. And yeah, I'd definitely suspect a thermostat that isn't opening all the way with what you're describing. Probably not stuck closed, but more likely not opening all the way either.

Are you running a 5 cylinder or V8?
 

Airborne

Just a regular dude
Messages
294
Location
Utah
It's the 5. I put the stock heat shield back on it. I leaned against wrapping it because of the rusting issues that happen.
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
My H3 has always ran 3/4 which seemed high for me but most say that is normal for the H3.

Despite this, I changed the water pump, thermo, new radiator and flush my system.
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
I also added pusher fan to help when idling
0401171551.jpg0401171551.jpg
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
I am gearing up to install the trans cooler. Just been lazy. This is probably the most important mod and should have done it first.

I have seen some improvement with Temps but nothing crazy.
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
In my opinion, you should immediately to the trans cooler along with it Pusher fans. I am no mechanic but was able to install my fans at least. Believe me when I say if I can do it anybody can!
 

alrock

El Diablo
Staff member
Messages
10,677
Location
Scottsdale
I would start with a thermostat and see what happens. Relatively easy and cheap troubleshooting step.
 

Airborne

Just a regular dude
Messages
294
Location
Utah
Thanks Alex, the tstat is what I was going to start changing out. Before I started busting out tools I wanted to verify temp variations like that are not normal.
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
Can007 what pusher fan and hood vents did you go with?

Initially I ordered a 16-inch fast but soon came to find out that I need a lot of modifications to make it fit so I settled with 2 10" fans. I got them from eBay.

As for the vents just got a saw and started cutting
 

Graham2990

Well-Known Member
Messages
132
Location
TN
I'd hazard a guess a trans cooler will make more of a difference in cooling performance than vents or pusher fans.

My trans temp dropped 20 degrees to around 165 on average after install.

Average engine temp is right around 185. I'll get to 197-200 on an 80+ degree day on the interstate going about 85.
 

Can007

Well-Known Member
Messages
374
Location
Palmdale, CA
I'd hazard a guess a trans cooler will make more of a difference in cooling performance than vents or pusher fans.

My trans temp dropped 20 degrees to around 165 on average after install.

Average engine temp is right around 185. I'll get to 197-200 on an 80+ degree day on the interstate going about 85.

Complete agree. I did the other Mods due to 100+ weather.
 

Airborne

Just a regular dude
Messages
294
Location
Utah
Thanks guys I will do the trans cooler when CJ is done with his new front bumper so I can do it all at once.
 
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