TDI300 Overheated on motorway

Hi all,

Hopefully I will get a bit of information from the people who really know how a TDI 300 engine works.

Here is the story, motorway cruising in a discovery tdi300, sat at about 75/80, notice the water temp was sat off the scale. pull over, turn engine off. it was at the end of a 2 hour motorway journey.

I popped the bonnet, expecting water to be hissing out from expansion tank, but, there was nothing, it wasn't even pressurised.

Am I right in thinking that it could be any of the following

1, blocked rad
2, jammed closed thermostat (doubtful due to the fact car had been driven at 75/80 for 1.75 hrs)
3, dead water pump/ pump failure
4, HG failure?

Having pulled over, there is a sensor on the top of the engine, this is no longer a sensor, but a pile of plastic gloop.

I have no idea how long the car was overheating for. I am almost certain ive cooked the head though, so that's deffo a job needing to be done.

Any help or advice on whats broken would be appreciated.

Does it still run?

yeah, runs very smooth and pulls well (drove it from top of drive to bottom, around 100 meters) without it getting warmed up.

dcc said:

yeah, runs very smooth and pulls well (drove it from top of drive to bottom, around 100 meters) without it getting warmed up.

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If it runs and dont smoke then I would just keep an eye on the oil and water and see how it goes.

I assume a new thermostat and waterpump as a matter of course??

My temp guage often goes off the scale on a run then drops right down to normal operating temp - I know theres a problem there somewhere which I believe to be an airlock.

As said keep an eye on the fluid levels and see how she gets on, could be no cause for concern.

Mine can be temperamental, check the wires to it and that you have a decent earth. Any other gauges acting odd?

Is your fan still fitted ?

If the switch melted then it got proper hot , you'll be lucky not to have to do head gasket , and head may well be cracked . When you say it runs fine , have you refilled with water or not ?

it hasnt lost any water, and yes, it did get very hot.

This wasnt a case of airlock as I have done runs of over 500 miles with no issues previously, and i dont think its the wiring as the gauge worked perfectly until now.

Check the condition of the rad, engine side.

Mine did exactly the same, couldn't see anything till we took the fan off to find the back of the radiator didn't have any fins left! All blown through, no cooling, and possibly worse, no oil cooling either!

New rad cured it.

level in expansion tank doest necessarily mean engine/rad are full ,only removing bung on thermostat housing and rad proves that ,and should be removed when filling /toppimg up so your sure ,when up to running temp ,top hose should be hot proving thermostat is open ,rad should be hot all over core when thermostat is open if not replace ,all pipes, heater /bleed pipes (rad and thermostat housing to expansion bottle)etc should be hot proving goog circulation , if temp sensor on top of head as melted then i too would be surprised if gasket is good ,they leak gasses to water way usually before actually blowing completely and power been noticeably lost

Thanks for the tips.

I was planning on getting the head skimmed and checked, if it were thought that could be the issue. I will for now check the bleed points on the engine for air and see how hot it gets. I havent got time to do anything before next week due to le mans, I will update you all when I return

dcc said:

Thanks for the tips.

I was planning on getting the head skimmed and checked, if it were thought that could be the issue. I will for now check the bleed points on the engine for air and see how hot it gets. I havent got time to do anything before next week due to le mans, I will update you all when I return

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get some decent brass bleed valves off fleabay, that allow you to bleed the system when hot. It makes life a lot easier.

The Mad Hat Man said:

get some decent brass bleed valves off fleabay, that allow you to bleed the system when hot. It makes life a lot easier.

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Like these

http://www.landyzone.co.uk/lz/f46/cooling-system-bleed-valves-174743.html

No
They will screw right through.
You need the flanged sort. Like these....
http://item.mobileweb.ebay.co.uk/viewitem?itemId=221045748737&kw=221045748737

guys, I have a 1997 300tdi. at 75 mph on motoerway the temp guage would read high. Just fitted a new rad. No more problems.

Just reading this and there does not seem to be any other symptomes apart from the melted sensor.

If the water was unpressurised and not gone down how did you come to the conclusion the engine was very hot? It had a 2 hour drive so the block, exhaust and turbo will be very hot anyway.

The reason I ask is that in the recent floods I went out playing and in some deep water I had the bow wave over half way up my screen and water came into the car from the scuttle panel.

While we had some chips I had the engine running to try and clear the mist from inside the Landy. When we got in to go the Temp needle was off the scale.

I have no fan so took it carefully up the road to see if the cool air would bring the temp down but no luck.

Stopped and checked the engine and same as OP, no pressure in the bottle, plenty of water and no other signs of a problem.

The needle stayed on max for about a week or so, even when stone cold, and went back to normal after about 2 weeks.

Must have got some water in the electrics.

So, just wondering if this could be the same problem? Does the needle start of at the bottom as normal when starting from cold?

had the same thing today - 300TDi overheated - found to be thermostat failed . hopefully nothing more major. still waiting for motor to be returned.

The Mad Hat Man said:

had the same thing today - 300TDi overheated - found to be thermostat failed . hopefully nothing more major. still waiting for motor to be returned.

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Fingers crossed for you mate ... :5bchillpill: