Coolant Loss from Expansion tank/etc.
 

2004 Discovery 2 - 4.6 v8

Hello. I'm starting a new thread because I've done major work to my truck about 2 1/2 years ago so I think I can rule certain things out like a cracked block.

Here is the state of my truck. I did have a cracked block when I got it 3 years ago.

Now it has (as of 15000 miles ago):

1. Rover Cannibal top hat short block, new lifters, timing set, ARP head studs, etc.
2. Valve Job, and shaved heads (original heads)
3. Auto meter oil pressure gauge
4. Custom Auto Meter Temp gauge install on intake water pipe outlet. I have actual coolant temp coming out of the block/intake manifold. Real temperature gauge, not radiator temperature.
5. Radiator flush at time of block replacement.
6. New thermostat, coolant hoses, and radiator cap at time of block replacement.

Here is what is going on.

I pull a 4300 pound trailer about 6 times a year through the Adirondacks. Boat/Trailer combined weight.

When pulling the boat, the truck, from what I can tell, blows coolant out the expansion tank when towing. I don't think it is eating it, as far as I can tell. The truck doesn't overheat even when pulling up big hills. My dash gauge never moves. My auto meter gauge (real temp) is always between 190 and 210.

If I'm not pulling the boat the truck never seems to lose much coolant. Between oil changes I may have to top it off.

I have coolant dye running in the system. The hoses, water pump, intake, etc. are not externally leaking. I've checked them with a black light.

The last time I did the block check it did not change color.

Any advice on what to do?

Unfortunately, I have secondary air. So If I am going to pull the intake manifold I might as well just pull the heads as well.

I'm wondering if there are some things to run through before that, outside of the normal things a mechanic would do to a normal coolant system that wasn't in a Land Rover.

Thanks in advance.

180F stat from LR source (not Motorad)? One member posted about towing a trailer in the desert at 109F outdoor, with 195 temps. And 183 when not trailering.

Coolant cap might just be bad, and they are cheap. It might be the source of a sneaky-while-driving leak. You can zip tie a paper towel (blue is good) to the overflow line to see it if is "peeing" when it should not be. Some have posted about a "will fit" coolant cap that has a higher pressure rating, that should not be used. I found one on my other ride when I pulled into the parts store, and noticed a row of spots on the pavement that tracked the same arc as the tires.

BTW, the OBDII value for coolant temp is from the sensor inside the intake adjacent to the water outlet. The radiator temp sensor is a device for detecting low differential on the cooling system, indicating a stuck open stat, don't believe that value is shown on the OBDII port.

dyes and black light are cool but you have to be able to see the leak in order for them to help.
A simple 1/2hr pressure test a 16 psi will tell you if you have a leak even if you can see it, the psi will stay the same or it will drop.
If you topping off your recovery tank with every oil change I would suspect you have one.

You have put so much into that engine. Don't kill it now.

OK so
180 degree stat from Rover itself not Motorrad - that is $70.
Radiator - Rockauto - About $200.
Hayden HD fan clutch $70 from eBay.

You are pushing your cooling system to the extreme towing in the mountains.

You need every bit of cooling capacity you can muster.

You must be boiling somewhere and creating pressure.

Either improve the cooling system as above or
change the mixture to a higher boiling point.

For towing - I would do the trifecta and change the big three

stat
radiator
fan clutch.

And of course - A/C off.

Thanks for the suggestions. Pressure test, then if OK the stat/radiator/fan clutch are probably due even though they are all functioning. Has anyone had my issue that actually resolved it by replacing the three?

Due to the dye solution I'm already using I know that if their is a leak, it is internal. Lovely.

What about the throttle body heater? Has anyone genuinely had that cause this problem as well? I'm going to pull off the air cleaner assembly and check the inside with the black light later today.

Question: If I bought a Genuine LR TStat from roverparts, what temp are those set at?

When towing it usually stays around 190-195, even with the A/C on, in 95 degree heat. When I am idling is when it rides up to about 205-210, and then settles back to 180-185. Where my gauge sensor is I see a lot of variance though.

The Land Rover dash gauge is right in the center from about 165-210, by my gauge. I still don't understand why they designed it that way. It is almost like an analog idiot light.

The ODBII is reading the sensor on the manifold. If anyone is interested, that is why I braised the autometer boss onto the outlet pipe between the alternator and A/C. You always know exactly what the coolant system is up to.

I've worked on a lot of vehicles. This one is definitely the most interesting.

The other thing that I forgot to mention is that I/we hand ported the heads when doing the valve job. If anyone ever has their heads off, I highly suggest it. Definitely runs very smooth, and has better torque.

The LR t/stat is a 192 style t/stat and not recommended when there are better 180 degree units available.

re: It is almost like an analog idiot light.

Thta's the facts, jack! The programmers for Bosch created a software bug that lulls owners into the belief that all as well - until deep fried.

I have an interesting update.

My truck is actually doing this, now that I've watched it. It seems happy with the coolant filled to about an inch and a half below the full mark. After it gets to that point the level is stable. It has been since my last post.

First off I ordered the expansion cap. Mine is a bit crooked when tightened, sometimes. I'm going to change the thermostat, and cap, before the winter.

I have attached a picture of my dash driving between Syracuse and Utica, someone took it for me. Notice the good oil pressure and temp after driving 70 on an 85 degree day, for 45 minutes.

Good oil pressure. Here is pix of one owner with the 180F stat swap. Be sure to get real Rover, not Motorad stat.

I have read in other threads that others have noticed the same thing. I had my cooling system flushed and refilled after replacing a cracked expansion tank and it also pushed coolant out until it settled a little below the full mark.