overheating....again

[Serg911]

I've got a 1999 DII with just over 110K miles (110,4XX) and lately, it has been nothing but a headache trying to keep it from overheating. Today I replaced the coolant pump feed line, poured the coolant and took the truck for a short test drive. Within 2 miles of driving at city speed (25-30mph) the needle started climbing up and up, but managed to get home before it got all the way to the top. After letting it cool down for a couple of hours re filled it with coolant and the subsequent drive test produced the same results, overheating.
There is no coolant leaking from any of the hoses as confirmed by inspecting each connection and no coolant on the ground when stopped.
I assume the coolant is ending up in the block as the symptoms are similar to what I had experienced -just over a year ago- when the coolant pump gasket failed and letting coolant into the block. Back then I had some of the hoses, coolant pump, and thermostat replaced. Since then, the thermostat has failed and replaced again. The plenum heater plate gasket failed and had it replaced along with the two hard lines that connect to it. About a month ago, one of the upper coolant hoses failed and replaced. Last week the lower (coolant pump feed line) failed and I replaced it today....and here I am, still dealing with overheating problems.

More than a rant, this is both a warning and a plea for advice. What could be causing this constant overheating problems? 110K is rather low mileage, the truck has been well cared for as far as regular maintenance, and never abused. Never taken it offroad or towed something. what on earth is happening?

 

[Ed Cheung]

U sure u burp all the air out?

 

[pdxrovermech]

your engine is shot. you and 1 out of 2 disco 2 owners have this problem. worst engine ever.

 

[messar]

My guess - head gasket

What I'd check first though:

1 - Ed is correct - was the system bled properly when you refilled it? If not, you need to start there, and make sure there is no air in the system.

2 - Are you loosing coolant? Do you hear a waterfall noise from the heater? If yes, where is the coolant going?

3- From your description, it sounds like hoses and gaskets are failing - this means that the system is pressurizing way more than it should. Once the system is bled, and you close the overflow tank cap, how long does it take for the rad hoses to get hard? If it's right away, head gasket (or worse)

4- If the coolant is disappearing, it may be being burnt through the engine - pull the spark plugs, and see if any are really clean - this will indicate where the leak may be.

5 - If none of these are happening, is the radiator working OK? does it get hot all over when the car is running?

Matt

 

[Serg911]

what is the process for bleeding the coolant system on this engines, this morning I saw a puddle of coolant underneath the truck, I'm really hoping it's leaking from one of the hoses and not what I had feared -the engine-.

I'll follow Ed and Messar's advice and see what happens.

 

[Ed Cheung]

Bleed it with heater on, and when it reach operating temperature with t-stat open. Open the bleed screw just enough for the air bubble to come out. and keep feeding coolant to the expansion tank when it is low.

After bleeding and when the coolant is cooled off, you will see the coolant is low again in expansion tank so top it off again.

 

[messar]

It also helps to lift the overflow tank as high as it will go when opening the bleeder screw.

Matt

 

[pdxrovermech]

and dont try to tighten the bleed screw anymore than a baby could.

 

[crown14]

and dont try to tighten the bleed screw anymore than a baby could.

... with their foot

 

[RoyLuke]

My water pump went out and after replacement it ran consistently hot. I found out that the radiator gets progressively bad and the new water pump was just too strong for it. Got a new radiator on ebay and the temp was solid as a rock.
Roy

 

[Serg911]

Gosh, I hope I don't have to change the radiator.
Here's an update: I bled the system as per instructions gathered in this forum (got the passenger's side on a ramp, loosened the bleed screw by the T connection located at the top of the fan shroud, opened the expansion tank, poured coolant while cold, ran the engine with heater at full blast for about 20 minutes, shut the engine off and let it cool for a couple of hours then refill the expansion tank and massaged the hoses to work the bubbles out of the bleed screw, refill to proper capacity then ran the engine until it reached normal operating temp. and drove it for a few blocks without the needle going past the half-way point)
didn't dear drive it past a few blocks, I'll try it tomorrow maybe. The oil seems clean, so I'm very hopeful I've cured its ailments.

will update status after a few miles
thanx

 

[jimjet]

I think because its happening to me now also is.
You are going to keep bleeding it every couple of days or so because your pressurizing
the coolant system with a bad headgasket or leaking sleeve.
i bleed mine and its fine for a few days then i start hearing the gurggle in the heater core then i start getting
hot during idle but ok in cruise ,so i bleed again get the air out and im good for a few days but im using
coolant slowly.

im changing my engine with a new 4.6 in near future.
what a fucking money pit. but i love the truck.Its me.

Jim

 

[ptschram]

I assume the coolant is ending up in the block as the symptoms are similar to what I had experienced -just over a year ago- when the coolant pump gasket failed and letting coolant into the block. Back then I had some of the hoses, coolant pump, and thermostat replaced.

It is impossible for the coolant pump gasket to fail and allow coolant into the block. It had to be the front cover gasket that failed, yet you didn't indicate THAT was replaced.

It's not the engine that's poor quality, it's that God-#$@!%$ mothfukle convoluted, complicated and fragile cooling system with that abomination of a thermostat that is causing these problems.

I'm absolutely convinced this is it!

In your case, I'm afraid you're in for a replacement shortblock. You're likely to see the coolant loss become progressively worse to the point where seven tot en minutes after starting, it will peg the temp gauge and eventually, it will bow hoses off the thermostat.

The least of your worries is replacing the radiator! That would be the best-case, cheap fix to this problem.