No Compression after Exhaust Manifold Replacement D40

[user 51778]

I’m trying to determine why this vehicle eventually overheated and failed a compression test.

We had the exhaust manifold replaced on advice it was leaking possibly warped, and machining wouldn’t provide a long term solution.
After the exhaust manifold job was complete there were issues with bleeding the cooling system, (I should mention, the coolant was extremely dirty/ rusty and wasn’t replaced, suspect internal damage within the radiator) The vehicle was test driven a few times whilst the cooling system remained unbled. After some research the correct bleeding method was discovered, system bled, and we were away.
After driving down the highway for 15km, whilst the coolant temperature was monitored via the vehicle’s instrument panel, there was a sudden loss of acceleration, the temperature gauge went into the RED and fluttered.
Unable to start the vehicle, it was towed to a mechanic, a compression test performed with results showing no or low compression (more accurate results of the test can be obtained if needed) Advice given that a replacement engine would be needed to get the vehicle back on the road.
Previously to the exhaust manifold job being done, there was no issue with the cooling system.

Concider the above factors, 1. Disturbance of cooling system 2. Driving the vehicle whilst the cooling system was unbled 3. Cooling system unserviced.

What could have cause the vehicle to overheat?

 

[Old.Tony]

There are a number of possibilities that caused the problem, but it may not be the end for that engine. A few things to ask (this sort of thing is always difficult on forums because we can't view the engine ourselves).

1) How many cylinders had reduced compression and which cylinders (this is important)?

2) What condition is the radiator in? Is it intact, how old is it or how long since it was taken apart and cleaned?

3) The water pump is on the front of the engine at the base of the radiator fan. Has this been checked to make sure it's ok?

4) The thermostat is in the housing on one side of the engine. Has this been checked?

5) What does the liquid in the overflow bottle look like?

Let's start with that and see where we go.

 

[user 51778]

1) How many cylinders had reduced compression and which cylinders (this is important)?

2) What condition is the radiator in? Is it intact, how old is it or how long since it was taken apart and cleaned?

3) The water pump is on the front of the engine at the base of the radiator fan. Has this been checked to make sure it's ok?

4) The thermostat is in the housing on one side of the engine. Has this been checked?

5) What does the liquid in the overflow bottle look like?

G'day Tony,
Thanks for your input!
I don't have the vehicle with me right now, but I will answer what I can of your questions.

1) How many cylinders had reduced compression and which cylinders (this is important)?
Unsure, I'll ask the mechanic on Monday
2) What condition is the radiator in? Is it intact, how old is it or how long since it was taken apart and cleaned?
The radiator is intact, though as I mentioned the coolant is a brown/ rusty colour
3) The water pump is on the front of the engine at the base of the radiator fan. Has this been checked to make sure it's ok?
No, they have not checked the water pump
4) The thermostat is in the housing on one side of the engine. Has this been checked?
No, the thermostat hasn't been checked
5) What does the liquid in the overflow bottle look like?
As mentioned above, this liquid is a brown/ rusty colour

 

[Old.Tony]

I guess there's a bit of investigation to be done then. Here's some hope for you:

* IF two adjoining cylinders have low compression but the others are okay, you may just have a blown head gasket and may get away with just replacing that (and the head bolts, these must be replaced every time the head comes off).

* If it's only ONE cylinder with low compression, it may have either a damaged gasket heading to the outside of the engine (or the water jacket) or it's a cracked head. Not the end of the world: replacement heads can be obtained and they DO work.

* Rusty water will need to be cleaned out (completely) and a mix of at least 33% coolant should be used in future. The coolant has corrosion inhibitors in it.

Rusty water in the reservoir means it's gotten through the radiator and I would suggest that if the engine turns out to be salvageable, consider replacing the radiator with a new unit rather than making any attempt to clean it.

 

[user 51778]

That's some great info, thanks very much Tony, I really appreciate your time.
I'll let you know what we come up with.