Hey everybody. This is my first time posting here and I'm hoping to get some insight before shelling out the cash to take it to the dealer. This is kind of long because I don't want to leave details out.

I have a 1998 Discovery, and for the most part it's been a great vehicle (I've had it six years) with limited issues with the exceptions of about a year ago I had the head gasket replaced and replaced the fuel pump (yeah, don't run out of gas in one of these!) Otherwise it's been fine. About two months ago the oil light started coming on and then shutting off randomly. Every time I checked the oil it didn't appear to be leaking and the color was correct. I also checked the coolant and that was fine too. This light issue stopped as abruptly as it started.

One day I took it for a 45 minute drive and suddenly the truck started to overheat. I pulled over and there was steam coming out from around the cap on the coolant tank. I let it cool down and when I removed the cap the tank was completely empty. I filled up the tank again. No leaks. I started the truck. No leaks. I drove home and everything seemed to be fine.

The next day I started up the truck and watched...no leaks. Then, I let it run to get it up to normal temp and suddenly coolant started POURING out from the truck just in front of the front passenger tire. I shut it off, opened the hood and it was steaming from around the cap, but since I couldn't stick my head under it (coolant still pouring out even though engine was off) I couldn't tell where the coolant was coming from (somewhere around the tank.)

When it cooled completely, the tank was empty. Took the tank out and checked the tank, hoses, and connections. No cracks or anything on any of the hoses or tank. Checked the other areas and doesn't seem to be leaking from the radiator itself. Reinstalled tank, got new hose clamps (just in case). Filled it up. Repeated steps of running until it was warm- coolant poured out- steam coming from around the cap. Surmised that this is some sort of pressure problem.

Let it cool down, filled it again, loosened the tank cap, let it run until warm- no leaks and coolant level stayed the same.

So, in short, if the cap is loose the truck runs fine, doesn't overheat and doesn't lose fluid. If it's tight it loses all coolant and overheats. Seems like leaving the cap loose would be an easy solution, but I'm pretty sure it's bad to run your LR without a fully pressurized system.

Any ideas? And thank you in advance!

 

Have you replaced the coolant cap? It is supposed to hold pressure up to 18 PSI, then vent. If venting early, it can be a sneak leak that happens while driving and you don't notice it. You can also borrow a coolant pressure tester from a parts store, and pump up system to 18 PSI and wait 30 minutes for leaks to show up. Be sure to look at hose out the bottom of coolant container. If you have a sound like bubbles and water rushing thru pipes under dash that could be air - or exhaust gas (bad) in the coolant.

Also - if you depend on the gauge to tell you when things are hot, it can being pretty dang hot and gauge still looks OK. A scanner or Ultra Gauge is a lot better.

 

I'd replace the pressure cap and definately the thermostat..

The overheating and gushing coolant is a symptom of a stuck thermostat..

If after you do those two things, And get all the air out of the system, You're still having problems, Then it's time to look at the heads and water pump...

By the time the engine temp gauge reads hot, It's usually too late...And the heads warp and you've got new problems on top of the ones that caused the overheat...Hope that's not the case here...

Good Luck

John

 

You need a new coolant cap, as these guys said.
The oil light coming on while driving is a oil sludge problem.
There is to much oil sludge in the top half of the engine and it is not letting the oil return to the oil pan fast enough to supply the engine with oil.
You will need to have the engine flushed professorially unless you are able and willing to get dirty.

 

Here's a pix of what can hold the oil from draining down from the valve train area. It depends on oil galleys and gravity, and when they get full of gunk, like Spike says the oil will stay too long in the top of the engine and the bottom will just run out. You can take off the valve covers and poke a wire rod down in the galleys and unblock them. Of course a good solvent clean like BG is a plus, but it may takle some doing to remove a complete clog. A jumbo oil filter adds to your oil supply, so it can help also. You could also have a cracked oil pump, and certainly a mechanical pressure gauge test is a good idea.

 

My 98 Disco had a black coolant reservoir which are notorious for leaking around the joint around the middle of the tank. Not an easy leak to spot. Mine also developed an allergy to coolant. The truck would run fine but once you shut it down the coolant would flood out on the driver's side (RHD). Replaced with new "White" reservoir and everything is fine now. Is yours black?