Cracked coolant pipes

**LRT** · 17th May 2011, 02:43 PM

It seemed as though we needed to replace our thermostat, as the engine’s electric cooling fan kept running on long trips. Even when smoothly cruising at 100 kms/hr in overdrive, the engine temperature would rise over 100˚C. Previously it sat between 90-92˚C on a long trip. Before we could replace the thermostat, a pool of orange OAT coolant appeared around the inlet manifold nut beneath the air-conditioning compressor. The bolt was tight, so it looked as though we may have at best a faulty head gasket to replace. To temporarily seal the leak, we used SilverSeal sealant powder. This stopped the leak, but much to our surprise, the sealant seemed to increase the pressure of the cooling system and caused the engine to run at an even higher temperature, which was alarming. It was not long before the bleeder screw in the center of the top radiator hose sheered, causing a high-pressure leak of OAT coolant to spray all over the engine and stain every component in the engine bay.

We replaced the top radiator hose with the updated version, which has the bleeder screw relocated to the ‘T’ piece connection (Land Rover part no: PCH000460). We also installed a brass bleeder screw (Rover Parts Plus part no: PYP10008L-B) to replace the plastic screw on the updated top hose.

As we lifted up the coolant reservoir to bleed the system, we heard a series of cracking sounds. On investigation, we discovered that the plastic throttle housing return pipe and the radiator bleed pipe had snapped in half a dozen places. It was now obvious that the leak beneath the air-conditioning compressor had come from a hairline fracture in this plastic pipe that had become brittle after 12 years and 200,000 odd kms of use. We replaced these pipes with 5/16” (8mm) transmission fluid cooling hose, and rerouted the hose along the top of the engine, using stainless steel worm gear rather than spring hose clamps.

We have replaced the radiator cap, topped up the cooling system with new 50:50 OAT and water fluid, and much to our relief, the engine again sits on 90-92˚C on a long trip without the fan running. Nevertheless, we will replace the thermostat and the other radiator hoses as the engine is still running hotter than it should on short distance runs.

LRT

Tombie · 17th May 2011, 02:47 PM

12years and 200,000km I'd also be dropping in a new radiator and water pump...

**LRT** · 17th May 2011, 03:18 PM

Good idea Tombie, I shall do that. Is it best to settle for a standard replacement radiator, or try and source an Allisport performance radiator? LRT

**bee utey** · 17th May 2011, 08:54 PM

I won't go under the bonnet of a D2 without a roll of 8mm heater hose nearby... wretched plastic stuff!

**DiscoCam** · 17th May 2011, 09:49 PM

I was only looking tonight at a crumbling hose from under the reservoir to the fuel cooler (?). Where do you get the 8mm hose? What sort of connectors/clamps do you use? Factory ones appear to be single use?

**bee utey** · 18th May 2011, 07:43 AM

Originally Posted by DiscoCam

I was only looking tonight at a crumbling hose from under the reservoir to the fuel cooler (?). Where do you get the 8mm hose? What sort of connectors/clamps do you use? Factory ones appear to be single use?

Mackay Automotive make it. You should be able to order it from any decent auto parts store that has a Mackay catalogue. I just use Tridon worm drive clips, size MH005. The new hose is quite a bit thicker than the original, so you can't re-use any original clips.

**LRT** · 18th May 2011, 11:49 AM

I use GOSS 8mm Transmission cooler hose, which Burson Auto Parts sell to the length required. The GOSS part number for a box of 5m transmission cooler hose is TCH80L50. It is a quality product and is much thicker than fuel and emission hose as it is designed to withstand high temperatures. It will connect onto standard 5/16" (6.5mm) fuel and emission lines and nipples. It is best to use new stainless steel screwband or worm gear clamps (see attached picture) rather than spring or wire clamps. If joining the coolant hose onto very smooth plastic tubing, insert the plastic at least 3-5cm into the coolant hose and use two clamps to secure. If you need to join sections of coolant hose, I have found it best to use a 5cm or 2" piece of stainless steel fuel line, with a single clamp either side of the join. LRT

**northiam** · 18th May 2011, 02:18 PM

If that just a throttle body heater can you just delete it hoses and plug it?
Is this heater neccessary for aussie climate?

**LRT** · 18th May 2011, 07:12 PM

Yes northiam, it is just a throttle body de-icer and could be theoretically deleted in our milder Australian climate. I have heard of this being done successfully as a breakdown repair solution. When you look at a picture of the throttle body de-icer kit on the Rover Parts Plus web site, it is clear that there is not a coolant passage which allows coolant to flow through an idle thermo valve. Such valves usually have a wax pellet inside them which contracts when cold, opening a port and allowing additional air to bypass the throttle valve. However, on the Discovery, the throttle position sensor is located very near to the de-icer, so the malfunction of the de-icer may effect the overall operation of the engine management system. Since throttle body housing de-icer kits are relatively inexpensive, I would prefer to play safe and renew the component and use good quality coolant hose instead of blocking off the de-icer system. LRT

**imatt** · 18th May 2011, 07:53 PM

My throttle body de-icer was bypassed when I had my water pump replaced by Mornington Prestige, they also replaced all the brittle plastic pipes with quality heater hose, this was a couple of years ago and I have had no problem since.
Cheers Matt

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