First off I would like to thank all of the participants on this board (double thanks to Disco Mike!), I've been reading the board for a while in order to keep my truck on the road.

Last weekend I finished a head gasket replacement on my '03 Discovery (including the full machine shop job on the heads), replaced the oil and coolant and tested the truck, and that's where things got ugly. I took a short 4 block trip on flat ground (I realized then that I hadn't fully bled the system but had filled it until the coolant came out of the screw bleeder) and as I returned to my driveway the the temp gauge started to go over center and when I stopped the truck the hose from the radiator to the (new, but aftermarket from Atlantic British) thermostat let loose at the lower thermostat opening and spilled a pool of coolant on the driveway. After cleaning that up I reinstalled the thermostat with a new screw clamp, bled the system and started the truck with a code reader attached to the OBD II port. The temps soon rose over the 205 degree level of full thermostat open to the 220-225 degree level, because I was working on bleeding the system I had the coolant cap off and coolant started bubbling out of the top of the reservoir; this happened a few times before I called it a night. The only codes thrown involved the MAF which I had cleaned with MAF cleaner while reassembling the top end (and may need to be replaced). When the engine was turned off the coolant reservoir needed to refilled although it was not fully empty.

My shade tree mechanic guess (much of my previous experience is with Porsche 356 and 912 engines so obviously there's pretty limited coolant knowledge gained from those babies!) is a clogged or otherwise messed up radiator but I'm fearful of something worse - Does anybody have any suggestions as to how I should proceed? When I get home tonight I will check the oil and oil filler pipe for evidence of coolant contamination (any suggestions there?) but any further helpful suggestions would be very much appreciated, thanks in advance!

 

Bleed when cold, raise the coolant jug to give elevation, and don't be shy - let it bleed enough to get out all the bubbles, not just the first two or three. Messy, they should have built in a bleed hose. Then crank engine, top up coolant to half level, etc. With 50/50 premix, it won't boil until about 234, so you can leave off coolant cap while testing. Coolant cap with pressure brings boiling point to about 265+. Would expect to run in the 190's, some over 200, but when you get to 212 the electric fan is supposed to come on and help cool off in traffic. No sense ruining a new head gasket.

 

Savannah Buzz,
Thank you for your reply and suggestion. I should have mentioned that I hear the electric fan come on and that when I bled it through the bleed screw yesterday quite a bit of coolant did flow out. In the past I've bled the system with the coolant cap off and the heater at full without the system overflowing through the coolant cap, however yesterday it was bubbling and flowing out, the coolant just won't stay in the system when it reaches a certain temperature (around 220). Thanks again.

 

This may not be a good sign. The D2 has coolant flow thru the heater core all the time, there is no valve like older cars. Turning fan on high does cool off that coolant, but it won't change anything for bubbles. There is a $50 chemical test for exhaust gas in coolant (auto parts store, does 15 tests). It could confirm if you are still getting a head gasket or cracked block leak.

Radiator could be clogged, the water pump moves like 2.6 gallons a minute at 1000 rpm, so if you took large hoses of radiator and shoved a garden hose in the bottom outlets, you should be able to flow that rate and more in reverse direction. A radiator normally clogs in the bottom, so the bottom rows feel much cooler than the top. If you replaced thermostat with an aftermarket - severla posts about those sticking and not opening.

 

"You never bleed the coolant system with the cap off, put it back on before starting the engine. Also, only bleed the engine when it is stone cold if you want to get the air from the system. After bleeding it and driving it, recheck the coolant level before cold starting it, if it is down, refill to the cap and recheck 2 or 3 days later." from another thread by Mike. If you follow this and from the rave below you should get the air out. Having done this last week on my '03 then I know it works.

Rave:1-4 had nothing to do with bleeding

5.
Release top hose from retaining lugs on the fan
cowl, leaving the hose to rest on the lugs.

6.
Remove bleed screw from top hose.

l
'A' From 03 MY

l
'B' Up to 03 MY

7.
Unclip the bleed hose from the battery box.

8.
Remove expansion tank from its mounting
bracket. Slowly fill the expansion tank with
coolant, approx. 4 litres (7 pt).

9.
Raise the expansion tank approx. 20 cm (8 in)
vertically, coolant will drain into the system.

10.
Refill the coolant expansion tank until a steady
flow of coolant is emitted from the bleed hole.

11.
Fit the bleed screw then, with the expansion
tank still raised, continue filling the system until
the coolant level reaches the base of the
expansion tank filler neck.

12.
Fit expansion tank filler cap, fit the expansion
tank to its mountings and clip the bleed hose to
the battery box.

13.
Refit the top hose into its lugs on the fan cowl.

14.
Start and run engine until normal operating
temperature is reached, and check for leaks.

15.
Switch off engine and allow to cool.

16.
Check for leaks and top-up coolant to cold level

mark on expansion tank

 

If you are still having problems, call me.

 

Thank you all again, I will respond when I bleed it again, it's supposed to be 50 degrees tomorrow so the garage will be bearable.

 

O.K. now I am worried. 2004 Discovery, just installed an Ultra Gauge and got my temp. numbers. Its 34 degrees outside, around town temps run between 196 and 217, 204-206 highway. Now I have not leaked one drop of coolant in the last 8 months and the reservoir is always at the same level at the full mark and the Dex cool is clean. The A/C auxiliary fan works and comes on at around 212, radiator is clean on the outside. The fan clutch passes the less than a full turn test when hot. Heat comes on fast and is consistent. New serpentine belt, no leak at the TB and fresh oil etc.

My concern is my up and coming trip to NC, about a 750 mile drive. Temps will be up there. I have read the suggestions above, but I am not sure if I should really be worried?

 

re: 196 and 217, 204-206 highway.

Seems like you might be due for radiator flush, be sure there is no mud/leaves blocking the fins of any of the radiators (not just the one with coolant inside). It is doing what it expects to do, and the "wide open" thermostat position is just part of the design. You can also add a bottle of Purple Ice coolant treatment to drop a few degrees. Other than rad flush and thermostat change (only use OEM), hard to imporve on what you have.

When you are on the highway, neither fan is much of an issue. So that 204-206 simply reflects what your radiator in it's current condition is capable of doing.

 

I agree, you are a little high for this time of the year.
I would look at replacing the t/sat if not done in the last year, pressure test the coolant cap, which doe fail and if you have a radiator shop near you, let them look at it to see if it is worth cleaning, may not cause the plastic is too old and brittle and most won't clean well. If that is the case, then replace it with a new one.