Help needed, TD42 running hot on highway..

[garett]

i've got the opposite problem my needle barely gets off the cold line. got me a new thermostat to replace the what i assume is cut. mine also smokes quite a bit. like personal smoke screen when i floor it. mine isn't gauge issue as i can hold the top and bottom hoses in my hands.

i think mine came from darwin when it was new so i might have to check that timing as well.

[ashmccormick]

i've got the opposite problem my needle barely gets off the cold line. got me a new thermostat to replace the what i assume is cut. mine also smokes quite a bit. like personal smoke screen when i floor it. mine isn't gauge issue as i can hold the top and bottom hoses in my hands.

i think mine came from darwin when it was new so i might have to check that timing as well.

Watch out for the long bolt on the thermostat housing mate! It'll either come out easy, or youll have an intimate weekend with the Mav!

[nissannewby]

Is the bypass port the hose that joins onto the radiator filler neck from the thermostat housing? Is there a downside to blocking this off? I'm assuming I have everything in place, no leaks or coolant loss.

The bypass port is inside the thermostat housing. The idea of this port is so the coolant keeps circulating through the engine without going to the rad until there is enough temp for the thermostat to start working. This allows the engine to get to operating temperature quicker. Now the thermostat has 2 parts to it so as the main part opens it blocks off the bypass port to allow full flow through the engine and radiator. So if this port is not being closed by the thermostat them already hot coolant can just keep circulating through the engine.

You can use a welsh plug to block it. Or you could take some measurements to see if the thermostat is long enough to close the port when its open.

[ashmccormick]

The bypass port is inside the thermostat housing. The idea of this port is so the coolant keeps circulating through the engine without going to the rad until there is enough temp for the thermostat to start working. This allows the engine to get to operating temperature quicker. Now the thermostat has 2 parts to it so as the main part opens it blocks off the bypass port to allow full flow through the engine and radiator. So if this port is not being closed by the thermostat them already hot coolant can just keep circulating through the engine.

You can use a welsh plug to block it. Or you could take some measurements to see if the thermostat is long enough to close the port when its open.

Legend! Thanks mate I will have to pull it out and have a look at it to see if its functioning properly!

The thermostat is new and a genuine Nissan one so I just chucked it in without thinking about it. Are there many new thermostats that come defect from factory? Or just not opening fully etc?

[nissannewby]

Not really mate. Just to much tolerance available. You can modify the thermostat using washers or something similar.

[Sharky1]

Sorry couldnt be stuffed reading all posts. GQ TD42's were renowned for this. My mates does the exact same thing. 1stly, get a real gauge that gives you figures, not just a hot-cold reading. 2ndly, use Penrite HPR diesel 15 (15W-40) & nothing else. 3rdly, if your water pump was not genuine it's from china no matter what the store told you. I've gone thru 3 water pumps in 2 yrs in my GU TD42 to learn this. Also, is it losing any water? Check the quality of the seal around the radiator cap. If your rad is full alluminium, its prob chinese too & they often have poorly designed cap fittings. Also how old is your clutch? Old mate's overheating issues started shortly before his clutch went & even though he took all the same steps you have, the heating issue seemed to go away when clutch was replaced so I'm thinking minor slippage causing heat transfer & overworking engine.

[Kennedy]

My 1999 TD42 was always overheating when under pressure up hills or carrying/towing a load and was told by several mechanics it was a fault with this model. Fitted a recon engine/overhauled pump and new clutch at 350,000km and got no improvement. Fitted aftermarket top mount intercooler(pump tuned for intercooler) which improved it a little but still had to keep an eye on temp when under pressure as when the temp started to move it went quick. Fitted a 3 core, 75mm thick aluminium radiator(yes it is Chinese but I got it for $450) and temp only moves above just below half way mark when carrying a ton on back and 2 ton in trailer on a hot day.

I saw Bigcol's photo - 3,250rpm @ 105km/hr. Mine does 2,700rpm @ 100km/hr in 4th gear and 2,300rpm @ 100km/hour in 5th. I'm curious why the big difference.