QuestionI am a canadian liscened mechanic and I am have huge problems with my 2000 discovery 2. 4.0l V8 gasoline engine, without secondary air injection. Was driving on the freeway and my truck started to over heat. Pulled over and towed it to my shop. Repaired a small coolant leak under the throttle body and took it for a drive. I started loosing heat inside the truck and the temp gauge started to sky rocket. Thought I blew a head gasket so I did the head gaskets too. Everything came from the dealer including new head bolts. Tried again, samething. Took off the heads again and sent them out to have them checked. No problems with the heads but I had them planed to be safe. Pressure tested the block thinking it might the cracked. It held 30 psi of pressure for 9 hours. Put it together and tried again. Samething. Changed the rad thinking it might be pluged, changed the thermostat twice and checked three times for a blockage in the cooling system. I'm down to changing the whole motor which is about $12,000. Have any ideas? I'd hate to spend the money on a motor and find it's still doing the same thing. Like I said I'm a mechanic and have been for the last 15 years, so don't hold back on technical language. I NEED HELP! Oh, and yes both fans , mechanical and electrical are working and I've checked the water pump too.
AnswerHi Amer,
I'm in Quebec, Canada. Where are you located?
Have you checked the heater core (LR calls it the heater Matrix). To replace this baby, you have to dismantle part of the dash and the steering column. Yes, that's right - steering column!
The heater matrix acts as a heat exchanger to reduce coolant temperature as it passes through the matrix. Coolant emerges from the matrix and flows into the coolant pump feed pipe and recirculated around the heater circuit. In this condition the cooling system is operating at maximum heater performance. If the matrix is blocked or obstructed inside or out, it could affect the coolant temperature.
A cavity at the front of the manifold collects coolant flow from the engine. A coolant outlet pipe is sealed and attached to the front of the manifold and provides for coolant to flow through the cavity in the casting to the radiator top hose. A smaller port in the manifold also allows coolant to flow from the cavity to the heater matrix. The lower manifold also locates the Engine Coolant Temperature (ECT) sensor in a port in the front of the manifold.
The smart way to test this out is to flush the matrix via the engine compartment. As far as I remember the heater hoses fit directly onto the inlet and outlet pipes of the heater matrix, the case having foam seals. A possible blockage in the matrix could be flushed by removing the heater hoses from inside the engine bay and connect a garden hose (or pressurized hose) to the OUTLET pipe and open the tap! I've also read from other owners who warned that rodents like to nest in and around the matrix. You never know!
If the matrix is fried, the first sign is loss of interior heat. IF there's a crack or leak, you'll have fogging problems within the cab. Are you losing any coolant? Do you smell coolant within the cab? Some LR dealers have been known to repair cracked matricies but I'd weight this against buying a new one and feeling better that it wouldn't crack again.
Replacement is difficult. I'd leave this to the LR dealership. There are screws and an O ring on the engine side (simple enough) BUT there are also ducts, wiring harnesses and screws within the cab and inside the dash. Taking that dashboard apart to replace the matrix is a long job for someone who has not done this before. Even an ASE mechanic! Removing the steering wheel, dash facia, then central console is enough to confound even seasoned DIY'ers like me.
My guess is the heater matrix. You've done wonders so far...if you want to fool around with the dash to remove the matrix, send me followup and I'll put you on the right path.
Best of luck,
JohnMc
NB: Series II Disco's have trouble with sticking exhaust valves. Usually, the only cure is a valve job. You might want to take a look at your valve stems sometime. LR Canada would probably charge about $2500 to $3000 for this.
Its quite common and can reappear every 50,000 miles or so.
