How's that for a cliche thread title?

OK, so I recently did a new radiator and coolant temp sensor as well as a 180F thermostat.

Initially it was toggling from 190.4F to 194F. Last week it started to creep up to 195.8F every now and then and then a couple days ago it spiked at 197.6F.

Today it spiked at 199.4F. It ALWAYS and consistently goes right back down to 190, 194, or 195F. It seems the cycle that is being read from the PCM is about 30 seconds and it has never stayed for more than 1 or 2 cycles at the high temp before going back down.

Zero leaks, overflow tank is at good level, if not full. I watch the temp like a hawk, and am very conscious of the temp. Speed has no bearing, idle has no bearing. It's pretty cold here- basically around or just below freezing. The machine is kept in the garage right now and nothing on the floor and when I check the oil, it's clean and good. The coolant in the tank is clean free of debris.

Do I just have a bit of air in the system? If so, any nuggets of info on how to bleed this out? Or do I have bigger fish to fry?

 

Congrats! Those were great results. Temps should be around there and fluctuates few degrees.

 

Your temps are fine.

I have the gray 180° thermostat in my truck and my cruising temp is 188.6, drifting up into the mid 190s at idle. If I were you I might've expected a little lower as a cruising temp but what you are reporting is not a problem.

 

PHEW! I was more concerned about the swing than the actual temp. I'm still learning and shaking down the truck- which I love- but that it is moving that much kinda spooked me and when it moved to 199F for that cycle, I thought I should make sure.

I has gone to 197F and then when I idle for a couple minutes it goes back down. It has never idled at 197F. It really makes zero difference if I'm idling or at speed- the temp just seems to move around like I described from time to time. So the system is definitely functioning as it ALWAYS goes back down, I was just thinking I might have some air in the system or worse.

As an FYI, this is the Nissin radiator and Atlantic British 180F thermostat.

 

you may have a few air bubbles trapped in there.

these trucks are so much more difficult to bleed than a D1.

 

So I just went out and quickly did this procedure:

Well, I truly don't mean to be obnoxious, but have you read the procedure in the RAVE?

The bleeding procedure is on page 26-2-14.

(Steps 1-4 are putting hoses back together)
5. Release top hose from retaining lugs on the fan
cowl, leaving the hose to rest on the lugs.
6. Remove bleed screw from top hose.
7. Unclip the bleed hose from the battery box.
8. Remove expansion tank from its mounting
bracket. Slowly fill the expansion tank with
coolant, approx. 4 litres (7 pt).
9. Raise the expansion tank approx. 20 cm (8 in)
vertically, coolant will drain into the system.
10. Refill the coolant expansion tank until a steady
flow of coolant is emitted from the bleed hole.
11. Fit the bleed screw then, with the expansion
tank still raised, continue filling the system until
the coolant level reaches the base of the
expansion tank filler neck.
12. Fit expansion tank filler cap, fit the expansion
tank to its mountings and clip the bleed hose to
the battery box.
13. Refit the top hose into its lugs on the fan cowl.
14. Start and run engine until normal operating
temperature is reached, and check for leaks.
15. Switch off engine and allow to cool.
16. Check for leaks and top-up coolant to cold level
mark on expansion tank

No bubbles I don't think and it gushed out when I pulled the bleed screw all the way off.

I squeezed and squished for a bit, filled, and re- squeezed and squished and it seems good. I may go for a drive around the block and see what I can see, but I think all is well and I'm just being paranoid.

 

the method that jfall proposed in a post that was recently revived has worked best for me with my 2004.

i parked facing the truck uphill. loosened the expansion tank and raised it up. supported it with some boards. after making sure its lowest point was higher than the tee with the bleeder i took off the expansion tank cap and started the truck. i then had my son rev the engine while i stood guard over the tank and watched the trapped air bubbles come out. i also added coolant as necessary. after driving around tonight and monitoring temps with my ultragauge things seem back to normal. very little variation in temps

 

Thanks. I didn't get a chance for a spin tonight, but I will in the morning and will see if there are any changes. I'll try the above if I still get the swings.

 

In the morning before you start it, open the bleed screw and top it off with coolant. That will remove any trapped air at that high point. Parking nose up helps when opening the bleed screw.

 

I always bleed mine when the engine is cold. Start truck. Remove expansion tank cap. Pull expansion tank from its holder. Raise tank up holding it above front radiator hose. I never use the bleeder screw while doing this.