How do I diagnose a cooling issue?

**VladTepes** · 28th June 2011, 09:50 AM

How do I diagnose a cooling issue ?

300Tdi engine.(in a Defender)

The temp gauge normally pegs itself in the middle of the range, however recently the needle is over toward the red. – about the thickness of the red portion away from it. (make sense? )

I thought the coolant level might be a bit low so topped up with distilled water – no change.

I presume the other possible problems may lie with the
Thermostat ?
Fan ?
Radiator ?

How would I go about diagnosing whether each of these is operating normally or if it might be the culprit?

**VladTepes** · 28th June 2011, 12:19 PM

27 views so far... anyone ?

**RR P38** · 28th June 2011, 12:23 PM

Get your self a temperature probe.
Check air flow through radiator, is it blocked.
Water pump could need changing.
Radiator might need roding.
Whats the milage?
Has it got coolant in it? colour?
Fan drive belt slipping?

**adm333** · 28th June 2011, 12:27 PM

If it's not actually losing coolant then the 2 main areas to focus on are the thermostat or a blocked radiator, in other words if its holding its coolant level then it must have restricted flow and subsequently the ability to cool is reduced.

I would (and indeed have) followed these elimination steps..

1. test and/or replace the thermostat (consider the main hoses at the same time)
2. take it to a radiator place to get the radiator cleaned / unblocked.

The fan might be an issue if its only building up temperature when stationary which is easy to check as you can look and see. If it builds up temperature whilst driving along, then its more likely a blockage.

Dave

**VladTepes** · 28th June 2011, 12:41 PM

Anyone know how much it might typically cost to get a radiator rodded - drive in / drive out ?
Also costs of a 300Tdi thermostat and radiator hoses (for a Defender)

**adm333** · 28th June 2011, 12:50 PM

Probably around $200+ for rodding etc.

A quick search reveals a thermostat for a 300TDi at around $6

Hoses probably around $10 each

Reference
Defender--Cooling-Heating

Dave

**adm333** · 28th June 2011, 12:54 PM

Or for a local supplier....

Land Rover Defender 300TDI Thermostat | eBay

I use this guy a lot, and never had a problem.

Heaps of Defender parts by the looks.

**Blknight.aus** · 28th June 2011, 03:51 PM

viscous fan and coolant flow.

crack the fill plug off of the top of the thermostat housing and stick a thermometer in there.

cover the radiator intake with a towel and sit it on 1100ish rpm.

once its warmed up and the thermostat is open (you'll notice the coolant flow change) pull the towel, count to 10 then shut the engine down.

quickly remove the radiator shroud and put your hand in front of the fan onto the back of the radiator

if its cool then the radiator is blocked and needs rodding/replacing

**VladTepes** · 28th June 2011, 04:28 PM

Umm the thermometer is there for ??
(or is that how you detect the coolant flow change? )

What typeof thermometer ?

**roverrescue** · 28th June 2011, 04:57 PM

Vlad,
-First up check your earth to the factory 'gauge'.
-Second replace the factory 'gauge' with something that at least measures temperature.
Factory is resistance adjusted such that from ~80-100 degrees the need does not move.
As soon as a factory gauge starts to move north (AND its not an eathing issue) your getting pretty hot.

-Last radiator rodding I had was $200 for drop off/pick up radiator.
-If it is using coolant AND getting hot your more likely looking at a head gasket issue.

Steve

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