Yup, 95 x300, 4.0, my car loosing coolant. No puddles, no steam, no white smoke from the exhaust. The warning light comes on after about 120 miles. I can smell it under the hood, but not in the car (hopefully ruling out a heater matrix). If I was burning this much, I'm pretty sure I'd see white smoke

The temp gauge is slow to rise from cold., then gets almost to N, but wavers between the left 1/4 and N.

Do I just need a new thermostat? Maybe mine is stuck closed and it's blowing out the overflow while I'm driving?

 

No sneaky leaky spots? Darn

 

I've had two hard-to-find tiny leaks over the years: one where the thermostat housing is bolted to the cylinder head and the other at the heater hose at the rear of the cylinder head, roughly below the wiper motor

The first was just an occasional drip. I only discovered it (after many searches) while doing some other engine work.

The hose was a pinhole that eventually became quite a bit more than a pinhole :-)

Cheers
DD

 

I recently changed the thermostat housing gasket to the cylinder head myself and found the original to have been installed with no gasket sealant. so i installed the new one dry without any sealant, a few months later same problem. should I reinstall with sealant? what would you do?

 

Tim, I just replaced my thermostat. The engine was slow to warm up and ran 175- 180 on Ultragauge. It wasn't stuck open but opening too soon.
Jer, I used sealant on both the thermostat and water pump.

 

I have the lower radiator hose, and will replace the thermostat while I'm dropping the coolant. I'll use a thin smear of sealant on the gasket or the o-ring, depending on what mine uses (I actually like plumbers grease for o-rings, but since it should be stationary, I'll go with sealant).

Now if I could find the time to get to it.

 

I'm no jag expert, but if its really is blowing out the overflow whil you are driving you have a blown head gasket......

 

^ what he said...if it's blown, it'll find the path of least resistance, which is back thru the coolant system, vice the engine...this happened to a Mitsubishi Montero I attempted to drive from VA to CA a couple of summers ago. Overheated in western OK, blew the neck right off the radiator. Got that fixed, but then blew off again, and that's all she wrote...

 

OK, a lazy thermostat is the gauge issue, not the leak, so a new one is needed. Get the gasket at the same time. CAREFUL here, as some claim an o/ring seal, never seen one on an AJ16, and that housing will BREAK if you try. Take it out first, and observe if "your car" has a gasket or o/ring, just to be safe.

The coolant smell.

Bear with me a bit please.

The X300 has NO atmospheric coolant tank.

The X300 header tank has 2 level markings WAAAAAY down inside, one says "MAX", the other"MIN", that is the level of the coolant. I have seen a number where the tank is topped right up, or very close to full, and there is no room for expansion, so it comes out via the cap. This creates 2 problems, cap damage, mess in the engine bay.

The hose in behind the inlet manifold, coming from the back of the water pump, is also a known weeper, and will leave NO drips on the ground, been there with mine.

 

Notes in bold below

 

Good one. At least we are all on the same page.

You got to luv that smell, glad I have never one leak on the carpets, I reckon you would never get it out.

That hose on the X300 is so much easier than the earlier XJ40, did that on ours, and the inlet had to come off, no other way.

One thing I did forget is the electric heater boost pump, just rear of the header tank, they do weep at times, not common, but I have heard of it.

 

I unbolted my intake just to get a couple inches. I set the clamps that they can be accessed with a long socket extension without moving anything else, just in case they ever need snugged up.