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· Registered
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Discussion Starter · #1 ·
I know there are a lot of threads about bleeding coolant but heres something i havent seen anyone hit on.

I replaced the engine in my 2003 Disco with another used motor out of a range rover. I replaced the timing cover with the one off of the old engine, replaced wiring harness, and all that jazz involved in the swap. The motor is in, it runs GREAT, but i have one problem that i cannot conquer to save my life.

Here it is. Im pretty savvy when it comes to mechanics, so im stumped. When i try to bleed the cooling system i cant get all the air out. Or so it seems. When i start the truck up and let it get warm enough to open the thermostat and start circulating the coolant, it doesnt. The top hoses get nice and hot, while the bottom hoses remain cold. I replaced the NEW thermostat i put in, with the old one thinking that maybe the new thermostat was just faulty. No dice. Ive tried everything i can think of to get the excess air out but without the thermostat opening up i seem to be getting nowhere! Its as if an air pucket remains beneath the thermostat, not allowing the coolant to touch it in order to properly work as it should. Any help on figuring out how this is resolved would save me from driving this thing off a cliff.
 

· disco biscuit
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Mine never got hot enough sitting to open the thermo. When I drove it it peaked...seemed like it had a air or steam pocket keeping it from opening.

The coolant reservoir detaches from the mount real easy...lift it up with The screw out then fill.
 

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Discussion Starter · #3 ·
I drove it and it peaked like you say, but the thermostat still didn't open. I will give it a try again and see what happens! I just don't wanna overheat it and ruin this motor before I even get to enjoy it. I will definitely try lifting the reservoir to see if it aids in the process! Thanks for the tip.
 

· '03 Disco SE
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573 Posts
Get yourself an Ultra Gauge or an OBD-2 scanner that can read live data so you can be positive that the cooling system is faulty. I'm not positive that it is, as the lower coolant hoses do tend to stay cooler than the top ones.

Are you 100% sure you have the belt routing correct? It's easy to screw up and reverse the water pump's flow direction which might lead to symptoms you're describing.
 

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Discussion Starter · #7 ·
The belt is routed correctly. Bled the system took it for a drive and didn't make it around the block before it overheated. The lower hose is still cold. Didn't even make it to operating temp once on the road. Could it be a bad radiator or a bad waterpump? I have a hard time thinking one of those went bad since they were both working perfectly prior engine swap.
 

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You say it overheated.

How?

Did the gauge go to the hot zone, light came on? Did coolant overflow?

Why did you replace the engine?
 

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I too am having a similar problem after a motor install. The top hose gets very hot and full of pressure and the bottom stays cold to touch. Upon cool down the top hose sucks in on itself, when resevior cap removed the hose returns to normal. I cant afford to trash this motor so im not driving it to the point of overheating but i will need to bring it to operating temp to bleed any remaining air. Also im going to check the routing of the belt even though im sure its correct and the thermostat is brand new along with waterpump. I need to figure this out asap, so anybody with feedback is highly appreciated.
 

· certified idiot
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694 Posts
Just to echo PT here just dont assume the engine is overheating - measure it.

You have to think about the coolant flow in these engine differently, the thermostat is on the radiator return line not the input line. a huge amount of cooling is done in the heater matrix at idle. If you just idle the engine it will never put water through the radiator even if you use the cooler motorad fully open at 182 F thermostat with the weaker spring.

You have to bleed the radiator with the engine running and the heater set to full temp and full air flow. this will still not get air out of the radiator just the engine and heater matrix. then fill the reservoir and go for a short high revs hot run and let the reservoir fill the radiator then refill the reservoir.

Its a really good system so long as you understand the flow. Here are the descriptions and some pictures (thermostat from M Widner at dweb). I anticipate getting flamed but the reality is that at idle even hot you wont put very much water through the radiator.
cheers
Barri
 

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Thank you for the response gurunutkins. I too have the workshop manual at my disposal. The truck reads in the normal range while at idle but as soon as you put load on it the temp rises fast(havent let it reach the red with red warning light). Here in central PA we were just slammed with a snow storm so couldn t do much yesterday except dig out,but today im going to put the obd2 on and see where it reads at idle then on the road with load. Im going to research where the temp should be idle and in normal driving conditions.
 

· certified idiot
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The truck reads in the normal range while at idle but as soon as you put load on it the temp rises fast(haven't let it reach the red with red warning light)..
Remember you cannot use the temperature gauge on these trucks to see where the temp is - its an idiot gauge with only 3 positions - its not an actual indicator gauge. Thats why both PT and I said measure it with a scanner on the OBD port or a laser IR themometer. I have a scan gauge hooked up to my OBD port but any reasonable OBD scanner will read actual temperatures. These engines tend to fluctuate quite a lot on temp and the temp at idle in the head region can go up to 212F whilst the radiator remains relatively cool.
good luck with it
Barri
 

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Ok so i hooked up, at idle it stayed right around 196 and while driving on a short run to store it bounced up and down between 217-230. Is this an exceptable range? My thinking is it should be a little lower then that seeing as how its 30 degrees outside. Oh and yeah the idiot gauge,lol, stayed dead center the whole time. Thanks for any and all input.
 

· Disco 2 Greenie... I could use some help here and
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Ok so i hooked up, at idle it stayed right around 196 and while driving on a short run to store it bounced up and down between 217-230. Is this an exceptable range? My thinking is it should be a little lower then that seeing as how its 30 degrees outside. Oh and yeah the idiot gauge,lol, stayed dead center the whole time. Thanks for any and all input.
*following*

replaced thermostat, with PEM100990 - OBD reads around 197 once warmed up. Test drive & OBD results had coolant temp peak at 224 and then went back to 197. I am gonna take a stab and say the thermostat opened up which resulted in temp change -but- 224 degrees still seems HOT. Dealer said the thermostat was a pain to open once first installed and we are not confident that we have bled the line completely. About how long do you leave the bleed screw off while running to ensure no air left in system? :dunno:
 

· Mr. t
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561 Posts
I know this is a little old, but just for the public. 217-230 is too high.

In my experience 210ish should be about max. I know thermostats are not exact and differ from truck to truck and weather conditions, but 217 is too high.


Sent from AutoGuide.com App
 

· Mr. t
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561 Posts
I've been thinking about this a lot too. I've done a complete flush on my truck about 4 times now. I've always used the method of just raising the exp tank and bleeding from the bleeder screw.
The bleeder screw is the highest point in the motor, besides the exp tank which is, at the time, full of coolant and raised. So it just makes since to me that this should work.

Though during one of those drain/refills I replaced all of my coolant hoses and during that bleed, I bled and filled the motor first by filling through the top of block hose and bleeding out through the throttle plate( at the time it was still hooked up)
Then I finished off the bleed with the raised exp tank method.

Maybe the problem lies with replacing the bottom end and I just haven't had to deal with that yet.

Has anyone ever tried:
- doing the coolant bleed (per service manual i.e. raising exp tank)
-then once the exp tank is fitted back into position and filled to full mark, leave the cap off while letting the truck run under slight revs until fans kick on. And keep repeating this process in hopes that the air will escape through the exp tank, since it's the highest point in the system. Or even leave it elevated by hanging it with wire during the above described process.
- then once the truck cools and everything is back in it's proper position, refit the exp cap.

I'm pretty sure, as long as you don't have something else going on that the exp tank wouldn't boil over while doing this, but that's why I'm asking.


Sent from AutoGuide.com App
 

· Registered
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I had a similar air pocket issue on my current LR Dii series (2000) so I manually I clamped the top radiator hose and filled what ever I could fit in there that way, also topped off the overflow container. Now when I reattached everything and capped the reservoir I would let the truck idle at 1500 rpms with the heat on max... This helped force out a lot of open air pockets and each time I noticed the fluid drop in the tank, I would shut off truck, wait 10 min, uncap resv slowly, and kept topping it off, that solved my overheating issues and air pockets. Ignore typos, stupid iphone auto correct pissing me off.
 
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