300TDi overheated

[JB750]

OK, bear with me for the scenario:

2 weeks ago the stud for the serpentine belt tensioner snapped and the belt came adrift. I got the truck home, replaced the stud and the belt as a matter of course. Belt was really tight to get on (right one chosen from measurements and VIN) but I assumed it was because it was brand new.

Had some squeaking after a few minutes of running but nothing too bad so I put up with it until I could get round to the penny trick which I assumed would be the problem.

Driving locally this week, and the temp gauge seemed to be all over the place, almost like there was a dodgy connection. But the main thing was the heater blower was not even warm. Engine seemed to run fine, so I carried on. On the way home, the needle moved up a bit then towards the red, but this time it seemed to stay up there. So I pulled over and stopped the engine. I gave it 10 minutes to cool down, checked the water (which was low), topped up the level and tried to start her. It would barely turn over.

My first thought was it was nearing seizure so I left it alone and called the rescue boys.

I had 2 thoughts as to the problem:

1. Big airlock causing the lack of reading on the temp gauge and also overheating.

2. Water pump foobarred causing no cooling, but would not explain apparent water loss (unless airlock as well)

I took the water pump off and although a little on the rusty side, the vanes are still connected to the shaft/pulley and there is no telltale of water from the weep hole underneath.

Also, in the process, one of the long studs holding the pump and alternator/steering pump bracket has sheared!

I checked manually for compression and it seemed good, so I attempted to turn the engine on the starter with the injection pump solenoid disconnected and it was fine, so I reconnected the solenoid and the engine started fine. I have checked for water in the oil and there seems to be no sign of it.

I would appreciate any feedback on what may be/have been the issue, and also any advice on removing the support bracket/pump carrier.

Sorry for the life story but it saves lots of questions after

Thanks in advance guys.

JB

[squaddiefox]

Is the serp belt on correctly? Have you checked oil? Losing water would be a sign of a head gasket on the way out. Is it pressurising pipes? If the heater aren't working then I would try and bleed the system.

[Tanuki]

Lack-of-heater suggests you have a bad airlock and/or a 'diluted' coolant-mix that can't handle 100+ Celsius temperatures.

After your remedial work - did you actually add the manual-specified amount of corrosion-inhibitor/antifreeze mix to properly refill the system?

And did you do the necessary refill/bleed processes as specified in the Book-of-Words?

Whenever I've refilled LR engines I've run them at 2500RPM with the coolant-cap off, letting them freely expel any 'trapped wind' and adding 50% antifreeze/coolant mix so the filler's always full - then when the temperature-gauge is showing something like 'normal' I've floored the throttle and run the engine to the rev-limiter for a minute or so - which shakes-free any entrained bubbles.

When you release the throttle - within a few seconds you should expect to see a big 'burp' of trapped air in the radiator/header-bottle. Refill it to the max - then again run the engine to the limiter for 30 seconds.

Repeat until you're no longer expelling air.

[Boydie]

I've advised this before but obtain from your local hardware store some PVC water fittings, a 1/2" NPT male, a 1/2" - 3" reducer and a 12" length of 3" PVC pipe, join and glue them and screw the threaded fitting into the cap on the thermostat housing, Next, remove the cap off the radiator and fill the header tank until coolant is coming out of the radiator, this will be at the level point on the header tank if your 300Tdi is on level ground.

Refit the radiator cap and refit the header tank cap.

Fill the 3" PVC pipe 3/4 full and run the engine, keep the pipe topped up to 3/4 mark with coolant (any higher and it will overflow) untill all the air bubbles are expelled. Turn off the engine after about 15 minutes and remove your PVC "fill pipe assembly" and refit the cap on the thermostat housing, you should have no more air locks.

[JB750]

Thanks for all the replies guys

Finally managed to get the alternator/power steering pump/water pump casting off after much effing and blinding. Luckily after a little judicious anger with the blow torch and a pair of mole grips I managed to get what was left of the sheared stud out.

Not sure whether to re-use the old pump or get a new one. So, do I replace the pump or re-use the old one? It looks reasonable and seems solidly attached to the shaft, but I would hate to fit it and have another issue.

Has anyone used 'lr-trade parts uk' on eBay? They have good feedback but I've no idea what the parts are like.

Any suggestions welcomed.

JB

[Boydie]

If it's within your budget, fit a new pump - and use a genuine LR - not the "blue box" - 300TDi's dont have the best cooling system as is so dont mess with it. Secondly fit a new "P" gasket made from composite material NOT the LR compressable shim steel unit, these are only and good on brand new motors, any tiny corrosion on either or both of the two surfaces and they leak.

Where your bolts broke you might want to consider tapping out and fitting unicoils, when fitted into alloy they are stronger than the original tapped thread.

[squaddiefox]

I've used LR trade parts. Ask them for anything but britpart and they will point you in the right direction.

[JB750]

Well, replaced the pump got everything back together. Bled the system as best I could.

The heater seems to work fine once the engine warms up, and the temp gauge sits around 1/3, but I am not sure the thermostat is opening. The large pipe from the pump to the radiator/expansion bottle gets hot, and the expansion bottle seems pretty warm. But the top hose from radiator to thermostat housing, and the radiator itself (apart from the end where the pipes connect) is cool. I have bled the radiator via the top cap, the thermostat housing via the brass plug but I cannot seem to get the top hose or radiator hot.

Any advice would be gratefully received

[Boydie]

Did you install the thermostat the right way up with the tiny vent toggle at the top? I always remove this and drill out the hole to 1/8" if its not installed correctly you will get an air lock. As an addendum, the top hose on my Disco never gets hot while its parked, the thermostat simply remains closed until the truck is moving.

[JB750]

I didn't touch the thermostat housing, just the water pump and PS pump/alternator mount bracket. I guess I could just take the truck for a drive and check after a while to see if the water is flowing correctly?

I must admit, I always thought the thermostat would open once the temp reached 'normal' otherwise the engine could overheat if it raised and water weas only going around the block/heater?

[Boydie]

I'd check the thermostat first, if just to make sure its working - check this by immersing it in a pan filled with water, put it on the stove and heat it, stir with a thermometer - it should open at 80 degrees Centigrade, if it doesnt, replace it and re-fit it ensuring that the vent is at the top. From the sound of it, its partly open and need to be replaced. The 300TDi thermostat is a double valve unit that opens the bypass when cold to enable the block to heat up via the small by-pass hose and circulates water within the block, once the block is up to temperature the thermostat opens directing water flow into the radiator and closes off the top bypass, a complicated arrangement but it is a Land Rover after all.