New radiator and.. little bit of steam in front of vehicle when I come to a stop

I just replaced my radiator, lines and thermostat hoping to solve some cooling issues. Previously it was running half a tick down from 210 when cruising on the highway, and it would climb up a full tick past 210 under heavier load, I.e. going up a 9% grade, sometimes even a tick and a half.

After doing that work yesterday, last night when coming to a stop I would see a little bit of steam/smoke? in the headlights, similar to if it were foggy out. Wasn't able to find any leaks, and at idle it would stop after 15 seconds or so. Revving while stationary didn't recreate it. I was idling and crusining at half a tick down from 210 and under load (that 9% grade, with AC thrown on for extra strain) I was half a tick up from 210. I was thinking at first that the steam may have just been spilled fluids cooking off, but even after 40 minutes of driving it was still happening. Wondering if the radiator could be faulty? It's a Spectra from Rock Auto. Separately, would my temps not sitting at 210 all the time (a couple years ago it was rock solid at 210 all the time, though that was at sea level as opposed to where I now live at 5000-8500 ft) indicate perhaps a poor flush job? Or is there something else? Thinking about replacing the temp sensor to make sure it's not an issue with that. I did forget to grab a new radiator cap.

It's a 99 4.0.

Did you replace the radiator cap? They should be replaced every two years.

No, I realized this morning that I totally forgot to grab a new one. Will do that as soon as possible.

Radiator caps leak and most of it comes out as steam so you will never see the drips.

Make sure you get a 16 PSI cap, instead of 13 PSI.

Fluctuating temp is probably a t stat. Some change would be considered normal. Most newer cars change around 20-30 degrees or more but the temp gauge is not commanded to reflect this.

Rad cap change for sure. I always make then pressure test them at the counter when I buy them. Last time I bought one 3 out of 4 failed off the shelf.

Get the engine good and hot, then shut it off then watch for any steam for 15 minutes.

If no leak found, then run the engine at high RPMs, hood down, then pop the hood and see if there is wet line across the hood above the water pump pully-fan area and check around the water pump. Lastly check the water pump weep hole bottom side when cool for any sign of a leak.

Ecomike said:

Rad cap change for sure. I always make then pressure test them at the counter when I buy them. Last time I bought one 3 out of 4 failed off the shelf.

Click to expand...

Are most parts stores able to pressure test radiator caps? I never knew that.

montanaman said:

Are most parts stores able to pressure test radiator caps? I never knew that.

Click to expand...

Yes they have free rent rigs for pressure testing the entire cooling system and caps. I just make them pull one out and use it at the counter.

http://shop.advanceautoparts.com/p/...ingcampaigns&gclid=CPfmm4mvmNMCFc-1wAodzIYARw

I own one of the older more limited adapter versions that I just take with me in case their rental is rented out.

Good to know.

Thanks.

I had steam when coming to a stop, turned out for me to be the overflow line wasn't clamp tight enough at the radiator. Maybe check the over flow line is secure or and no leaks.

Good point, and radiator caps seal at two levels, if the top seal is not working the steam could come from a defective upper cap seal or damaged radiator inlet throat the cap screws onto or even the overflow nipple itself. Most leaks show up if you take a log hard drive, A/C on, then idle with the jeep still on in drive at a stop for about 4-5 mins, then shut it off, and pop the hood. At that point most leaks show up in about 5-10 mins as pressure builds.

iwannadie said:

I had steam when coming to a stop, turned out for me to be the overflow line wasn't clamp tight enough at the radiator. Maybe check the over flow line is secure or and no leaks.

Click to expand...

Thanks guys. Picked up a new cap (16lb, tested in the store).

Separately I think I found the leak at the upper heater line fitting, tracked it down via the steam after stopping after driving it under heavy load. I swapped the spring clamp for a hose clamp, hopefully that's fixed it.

I do wonder if the new tstat is bad, it seemed to take longer than usual to get up to operating temp, which, today, was one bar down from 210 (whatever temp that is). Under heavy load (going up a 9% grade with ac on) I got it up to 210. Kindof weird.. the tstat is supposed to be 195*, which I believe is the oem spec. Perhaps I need to either test or replace the temp sensor.

HobHayward said:

I do wonder if the new tstat is bad, it seemed to take longer than usual to get up to operating temp, which, today, was one bar down from 210 (whatever temp that is). Under heavy load (going up a 9% grade with ac on) I got it up to 210. Kindof weird.. the tstat is supposed to be 195*, which I believe is the oem spec. Perhaps I need to either test or replace the temp sensor.

Click to expand...

210 is the normal running temp for XJs. 195 is when the t-stat is supposed to start to open. I tried various t-stats, and finally settled with the OEM Mopar. It comes up to temp pretty quickly, and stays at that temp with no bouncing around in cold weather.