[georush]

I have a 1998 Discovery 1 with 149,000 miles. Recently had the head gaskets done, heads machined, new radiator, hoses, water pump etc. Put about 700 miles on it since. The other day while driving I noticed the temp gage go all the way to the upper band and then fall back to just below the center. Happened three more times over the next 20 miles, mostly when I accelerated. No tapping or reduced performance that I can notice, but I did see some dried coolant around the tank cap and the coolant is about 3/4 of an inch below the top of the tank. Waiting on a new cap before I pressure test and then move on to a compression test. Has anyone else experienced this? I live in fear of a cylinder sleeve slipping.

 

[V50_M66]

I have a 1998 Discovery 1 with 149,000 miles. Recently had the head gaskets done, heads machined, new radiator, hoses, water pump etc. Put about 700 miles on it since. The other day while driving I noticed the temp gage go all the way to the upper band and then fall back to just below the center. Happened three more times over the next 20 miles, mostly when I accelerated. No tapping or reduced performance that I can notice, but I did see some dried coolant around the tank cap and the coolant is about 3/4 of an inch below the top of the tank. Waiting on a new cap before I pressure test and then move on to a compression test. Has anyone else experienced this? I live in fear of a cylinder sleeve slipping.

Get another way to monitor coolant temp through the OBD2 port - the factory temp gauge is basically useless.
Could also be that you temp sensor is feeding erratic readings - may want to replace that too.

 

[georush]

Get another way to monitor coolant temp through the OBD2 port - the factory temp gauge is basically useless.
Could also be that you temp sensor is feeding erratic readings - may want to replace that too.

Good call. I was planning on isolating the easiest first: check for leaks, replace the cap, check the senders, bleed the system, etc. before I truly contemplate the worst-case scenario. Monitoring through the OBD2 port just moved to the top of the list! Thanks

 

[LVDaytripper]

Was the system completely bled? Sounds like coolant hitting air pockets that will spike up temps then go back to normal once air pockets passed. When you accelerate, pump pushes coolant faster through the system and when the air pocket passes through the tem sensor, sensor will pick up air temperature instead of coolant temp therefore showing the spike. This is at least how I understand the system.

 

[tyl604]

Happened to my '99 DII. You probably have air in the system. The attachment is for my '99 DII but yours should be similar. The coolant reservoir lifts straight up if you tilt it forward to let the two front bottom tabs slide out of the retainer. Do not unhook any of the hoses to the reservoir. Hope this helps.

 

[V50_M66]

Hold the truck at a higher RPM (1500-2k) when bleeding with the bleed screw - the water pump turning faster will help to get the remaining air out.
See this thread for more details -
Easy Bleeding Trick for the Cooling System | Land Rover and Range Rover Forum (landroversonly.com)

 

[georush]

I'm going to bleed it this weekend. Just received a new OEM cap, figured I'd wait. Hoping this will be it as I had planned on selling soon to fund other projects. Thanks all for the input and I'll let you know what happens.