Hi all, first time poster and new disco owner here...

I bought a 1999 disco 1 a few weeks ago. Don't know much about its history, but it has been a little iffy over the last 3 weeks, to say the least (its already needed a new fuel pump, transfer case work, and new catalytic converters... problems which were not apparent during the test drive)

Today I decided to take it on its first 1 hour+ drive up to the ski resorts from Denver, CO (I finally had the confidence it wouldn't leave me stranded...). On the drive home the check engine light came on and I noticed the engine temp was still pinned at the coldest setting... 1/2 hour into the drive. for the remaining hour of the drive the temp would slowly rise to about 1/8 the way up (still well below the indicated minimum temp line) then rapidly fall back down to the lowest setting, and repeat. I know its not the temp sensor because I had the heat blasting the whole time and I could feel the temp of the heater changing with the engine temperature read out. The engine is for sure running cold.

Yes it was a cold day... but it maintains a consistent temp in the proper range on even colder days.

Questions:

1) Is the check engine light related to the cold temps?

2) Is there an easy way to check the fault code of the check engine light?

3) I'm guessing the problem is the thermostat. I can replace this myself, easy. BUT, will the check engine light go off automatically, or will I need to pay an outrageous sum simply to have a mechanic reset it??

4) Is there anything else that could be causing the engine to run so cold?

 

Yes! Cel is showing low coolant temp and throwing a code. Sounds like the t-stat is stuck open. As far as clearing the code, either buy yourself an ultra gauge or code reader or, pull the batt cables. Should reset after 30 miles or so also.

 

Thanks for the quick reply, adigerol77!

I will replace the t-stat, and cross my fingers.

Are these code readers expensive?

Also, are the land rover t-stats readily available at chain auto-parts stores, or do I need to order them online?

Thanks again

 

1. You need to invest in a code reader/scanner so you can reset your own codes, and a very slick one is the Ultra Gauge, which also doubles as a display of all sorts of things, like coolant temp, with alarm points you program ($70).

2. A code scanner will show you engine coolant temp in digital fashion, from the coolant temp sensor.

3. There are two temp sensors on th D1, the one on the right in the pix is the ECU one, the single wire on to the left is the gauge sensor. Gauge will read like 8:30 - 9:00 in normal condition. Above 9:00 find out why. On mine, 132 F is the lower boundary of the "normal range" on the guage.

4. Your thermostat is either missing, or sticking open, or improperly installed. If found to be mising, the previous owner may have been trying to cover up over heating from head gasket, etc. Without a stat in the 100F summer I'll run like 135 - 140F. In your temps, that would be lower.

Stat is like $10. Put in a new one, either 190 or 180F, 160 is too cool and you won't have heat. Want one that has a jiggle device that rattles when you shake it, that lets gas bubbles pass by and not build up a steam pocket behind the stat.

Stat goes in that big hole in picture. Jiggle device goes at the top. Be careful when closing it up, if stat slips down, it can leave a crescent opening that does what you describe - runs too cool, but you still see some rise/fall in temp as stat opens and closes (making more flow). But it is always open some significant percentage because of the slip. I must confess here that I have done this more than once.

Stats are readily available at local auto parts stores, same ones fits chevys and fords. Spring part goes inside the engine block. You can test these stats in a pan of hot water on the stove.

You'ld have to know code number for specifics.

 

On line, Atlantic British, rock auto, rovers north. Check through the sticky post on the new to you and others. Lots of good post sale preventative info. Look at the ultra gauge, 99 bucks I believe and gives you live time data. Worst thng about our rigs is the temp gauge, never let it get above the 9 o'clock position for any amount of time. Download the rave if you haven't already and have fun.

 

Thanks for all the info and pictures, much appreciated.

Today the truck seems to be back to normal. Temp gauge is held steady at about 8:30. The error code was indeed low coolant temperature. I reset the check engine light and drove it for about an hour without it coming back on. I bought a 195 degree thermostat with the little jiggly valve, but the gasket wont be in stock till tomorrow. I will install when I find time as this dosent seem urgent.

I looked for a while and cant for the life of me figure out where the radiator fill cap is. All I can find is the reservoir. Do I use this to fill the coolant when I am all done with the job? I've never seen this design before. Does anyone have a link to a good write up about servicing the cooling system on these?

I hear the RAVE manual is supposed to be like the land rover bible and answer all tech questions... but when I download it its just a bunch of random PDFs with random titles... I've also searched these forums with no luck. I apologize if these questions are common and answering them is getting annoying...

 

Yes, fill through the res. check through the sticky section for a cooling system write up, can't remember but there's lots of part numbers and stuff. I know the rave is a pretty solid source, what exactly are you looking for.

 

You want pdf file L J, inside is the D1 shop manual, owner's manual, electrical manual, etc. You can also see it on-line through one of the links in my signature. You can use the top of radiator "bung" fitting to add coolant untl it overflows, then cap it, so that most of the air is out, then fill coolant bottle to mid point line as truck warms up. If you don't get all the air out you'll hear gurgles under the dash.

 

Sava...your truck is running very hot at 235 huh! As I mentioned on the other thread I'm running between 159 and 185 but usually around the 175 mark. My dash gauge is usually at 9 o'clock.

I'm still not convinced that the Ultragauge can be used confidently as a code reader. I plugged mine into both trucks which should have been throwing multiple codes and all I got was 1 code for each.

Sava...do you have the Ultragauge yet? I'm confused. I really think I need a real scanner.

 

Don't have an Ultra Gauge yet. Pix at 235 was to demo the gauge reading, had radiator covered. At the moment, I run a 160 F stat (about 8:30), one 1/8 inch bypass hole in the flange, stable at 158 on highway and maybe 160 - 162 in town. May move back up to 180 or 170 if I can find one of those. My 195 was "spiking" to 239, maybe HGs are only a few months away.... 15 mpg now, my best has only been 17.