Hi Guys,

I am relatively new to the board but have been reading the treads for years and have got lots of help from it.

Here is what I have just completed on my 03 Discovery.

-Previous owner had a sleeve replaced and the block rebuilt, heads rebuilt and new head gaskets just prior to selling me the vehicle.

-I have since decided to take on additional work as there were some oil leaks and such post rebuild. I just finished the following:

-Timing chain/gears
-Oil pump
-Water pump
-Thermostat (got the soft spring from AB)
-New pulleys
-New transmission filter/service
-Switched to rotela t6
-Re-did the PCV valve system
-Rebuilt the PS pump
-New coolant temp sensor
-New brake servo vacuum fitting
-New muffler
-All new brake pads and rotors

Needles to say its been a long winter and I want to drive this truck!

So here I am trying to bleed the coolant, thought I did it right, went for a drive and the needle on the dash started to creep up (scarry) by the time it got to 2/3rds the way up I stopped the truck let it cool down. Then got back to my drive way.

Let the truck cool down overnight, went back out this morning to see if by raising the coolant tank and opening the bleed valve I could get more air out. No air appeared to come out... Went for another drive and the same thing occured. This time I noticed that the lower rad hose was not nearly as warm as the top hose and cooled down very fast. Forgot to mention I am getting good heat inside the truck.

I have verified the proper belt routing. No issues there... Other problem I noticed was a big driveline vibration as I was decelerating with my foot off the gas at a stop sign. Will have to worry about that one after I figure out the overheating/coolant bleed Issue.

Please help.

 

Suspect radiator is not 100%. If lower rows of rad are cooler than top rows by more than 10F you could have a blockage. You can use an IR thermometer to check that. As for the dash gauge, PLEASE get a scanner that can show live data. With all the work done you are looking at the temp thru a device that shows 50% from about 130 - 240F. With a scanner you can see heat creeping up way before gauge moves off the middle and you do more damage. The ones shown below are the Ultra Gauge. Note factory gauge position.

 

I hope I have not already caused damage by letting the dash gauge creep up to 2/3. I work at a Nissan (sales manager) dealer and will be taking a obd2 tool that reads off engine temp home tonight. I fear that the AB thermostat (Motorad) is a piece of Junk. Seems other people suggest testing it in a pot of boiling water.

The rad was changed by the previous owner during his rebuild. Its one of those Nissens and the fab date is in 2012. The truck has less then 6,000km Since the rebuild, you think it could already be blocked up?

 

You said you changed out all the pulleys. Did you route your belt correctly? Spend $70 and get you an Ultra Gauge to monitor the temps. I personally have had 2 Motorads DOA and a 3rd fail within 6 months. So I don't trust them 1 bit!

 

If it was cooling efficiently before the work, it's highly likely you put something back together incorrectly.

First, I'd double check the belt and hose routing, and be sure the thermo is positioned correctly.

Second, I'd bleed the hell out of it. So, carefully elevate the reservoir (don't break the hard plastic hoses!), open the bleed valve, and tap and massage the hoses until no bubbles are visible. Last time I did it it took me 15ish minutes to get a decent bleed, and I still get waterfall noises under acceleration which means it's still not a perfect bleed. It's a pretty big pain in the ***. I suspect this is your problem.

Whatever you do, don't overheat it! These things blow head gaskets like crazy, and overheating contributes greatly to that problem. You're doing well so far, so just make sure you fix the problem before you start driving it.

 

Thanks guys for the fast replies, happy to find some help. I will take the thermostat out tonight and test it in boiling water. Any special way of doing this? I will then try to restart the bleeding process. To what extent should I drain the system back down and how should I best accomplish this? Oh forgot to mention I have also now replaced the top rad hose due to bleed valve failure. Having a great day.

Thanks

 

Also while I am trying to resolve this issue, what would be the maximum acceptable temp in deg F. before I am in what is considered the danger zone. I picked up a Mac tool scanner that will give me accurate temp for tonight.

 

You don't need to drain the system at all in order to bleed it. Check out the RAVE, it outlines the whole procedure.

I've never tested a thermo, so I can't help there. One tool that's useful is a infrared thermometer. They're ~$25 at a parts shop and great for diagnosing this stuff. So you could start the struck and measure hose temps to determine when/if the thermo opens. Hell, you could probly just feel it with you hand. Just don't get distracted and overheat it.

If you are running a 180* thermo, temps should never get over 200. They should really be more in the 190-195 ballpark or less. If you break 200, the system isn't working correctly. That said, the max temp before you do damage is arguable. Personally, and I'm kinda guessing here, I'd call the danger zone around 220, because at that point you can just shut it down and it shouldn't boil over. But I wouldn't drive it if it's breaking 200* with a 180* thermo, because something isn't right.

 

Ok so here's the update!

I took the thermostat out, put it in boiling water and confirmed with visual inspection that it opened and also allowed for free flow of tap water.

Bleed the system again as per rave instructions and suggestions.

Ran the engine and monitored it's temp using a obd2 tool. Engine got up to 220 and the thermostat never opened as the lower rad hose was stone cold and pressure was building up in the top hose.

Thoughts?

 

Well, I'm not sure what I'd do next.

1. I think I'd remove the bleed valve and crank the truck to see if coolant comes spraying out. This seems like a simple way to verify that the water pump is actually pumping. You might pull the fuel pump relay first so the truck doesn't actually start.

2. Then I'd pull the hoses from the radiator and stick a garden hose in the top to see if the radiator seems clogged. Buzz may very well be correct (again). If the truck was running fine before, I wouldn't suspect the radiator. But it's possible the previous owner blew the head gaskets by overheating it because of a bad radiator. Also, since the truck has been sitting for months, any dexcool pooled in the radiator would have turned to sludge.

3. If you are running dexcool, drain that crap and put in green coolant. It's arguable, but there's a lot of evidence that dexcool turns to sludge if you look at it wrong.