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2004 Land Rover Discovery - Slow Cooland Leak

I have a 2004 Land Rover Discovery which I purchased new in 2005.

57K miles on the clock…

Car runs beautifully, with only a few minor cosmetic and mechanical problems which were all addressed by the dealer(s) under warranty.

1. However, one problem that the dealer never could figure out is that the alarm system sometimes looses its mind.

Basically, it would occasionally refuses to lock the doors and arms the alarm. It appears to think that there is at least a door that is still open.

I could still manually lock the doors using the button inside the car, though. Of course, the alarm system is not activated.

I also tried to activate the alarm and lock the doors manually by inserting the key into the driver’s lock. No good either.

If I leave the car for a few hours or over night, the problem disappeared.

Any idea?

2. A couple of months (2 to 3) ago, the car developed a very slow coolant leak.

I first noticed this problem when I smelled coolant from either the driver front wheel well or hood area after a 15-20 minute drive (to and from the office).

I could drive 1500 mile and then check the coolant level. It would be about 2" lower then the full mark when the engine is cold.

So, it seems to me that the leak is very slow. No trace of coolant on the ground or the engine compartment.

The local shop has looked it over and couldn’t see any obvious leaks. Also, done a pressure test and no indicative conclusion.

However, the tech said that the leak is most likely around the manifold area which requires lots of work to get to.

Looks to me that the throttle body, fuel rail, alternator, etc. - have to come off to get to the manifold.

The quote for the repair is about $700.

Any idea to help me isolate the leak? And, is the estimate reasonable?


Sorry to tell you but that v8 engine suffers from head gasket failure at around the 50 - 55,000 mile mark ~ it’s almost clockwork. The head gasket is a thin tin type that is prone to slippage caused by the different expansion rates of the block and heads.

These head gasket failures tend to creep up on you and are rarely a sudden breakdown. Look for excessive water vapor at the exhaust pipe to signify a minor internal leak, which is usual.

You can also check the valley pan gesket end seal bolts to make sure they haven’t worked a little loose, another common problem but generally it the head gasket, if the leak is external it’s usually at either end of one of the heads.

That is good to know. Do appreciate the tip!

Also - if there is an internal leak, should there be traces of coolant in the oil? I checked the oil weekly, and it does not appear to have any visual mix of coolant.

Also did check for water vapor or white smoke at the tail pipe, but not conclusive.

Thanks again.

NP - These leaks tend to be very small as you’ve discovered, and this amount of coolant get’s boiled off by the hot engine surfaces.

They are therefore notoriously difficult to detect. If it’s external the water is usually vaporized before it even make it out of the head / block joint. All you get is that infuriating whiff of coolant now and then.

Since you’re not getting any steam at the tailpipe and you have smelled coolant I’m guessing the head is venting outboard. The only way forward is to use an inspection mirror and flash light to rigorously inspect for leaks - if you’re really serious get some French chalk or neutral talcum powder with a dust puffer and dress around the valley pan intake area and head / block joint this will immediately show up even the smallest leak even if it’s vapor - note steam itself is invisible, it only becomes visible when re-condensing. The powder is easy enough to wash off when you’re done - don’t use perfumed talc unless you want your engine bay smelling like a boudoir for the next six months.

I’m assuming you’ve checked and cleared the water pump itself but there are 2 other common failure points on that V8:

Check the molded heater hoses at the front of the intake assembly, they have a tendency to rub on the distributer and become porous - again chalk will pick that up.

Very rare - but does happen. The flat rear face behind the water pump, that rear face is part of the engine timing cover and has been known to become porous due to water pump cavitation and can develop very small pin holes. Though they are impossible to see they are large enough (of course) to permit coolant leakage - again chalk yadayadayada. The timing cover is hugely expensive to buy and replace, the only time I had one of these I stripped the pump out and used liquid metal to coat the inner surface of the timing cover - it worked fine and never leaked again.

Let us know how you get on.

Great! Thanks so much for the help.

Kinda busy in the next few weeks, but I plan to address this after that.

Stay tuned!

Regards. DLe.