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740 Head gasket milky sludge in the coolant

RR

RR

Member
Joined
May 15, 2003
Location
Northern CA
Ok, so I bought a 1992 740 wagon, knowing it needed a head gasket. What I did not know is the coolant has the milkshake sludge everywhere.

I am in the process of removing the head to refresh, but really need to get the milky sludge out of the engine, heater core and radiator.

Has anyone perfected or successfully done this cleaning flush?

I realize it will take some time, and have seen some videos with Ford trucks; just would prefer insight here.

Thanks in advance, Rick
 
If you have milkshake in your radiator chances are the transmission fluid heat exchanger in the radiator is bad. Do you have milkshake in the transmission?
 
hiperfauto said:
If you have milkshake in your radiator chances are the transmission fluid heat exchanger in the radiator is bad. Do you have milkshake in the transmission?
Click to expand...

No the tranny fluid is clean. The car was overheating and I know the milky sludge is in the head, radiator and coolant reservoir. A shop did a compression test and diagnosed a failed head gasket.
 
Okay, it sounds like the heat exchanger isn't the problem. It's just a little unusual for a blown head gasket to contaminate the cooling system unless it happens to blow where oil under pressure is pumped to the head. Usually coolant leaks into the crankcase or combustion chamber confining the contamination to the engine.

You could try some of the radiator flush products available at any auto parts store. Some shops have cooling system power flush equipment but they typically charge $100+ for the service.
 
Last edited:
hiperfauto said:
Okay, it sounds like the heat exchanger isn't the problem. It's just a little unusual for a blown head gasket to contaminate the cooling system unless t happens to blow where oil under pressure is pumped to the head. Usually coolant leaks into the crankcase or combustion chamber confining the contamination to the engine.

You could try some of the radiator flush products available at any auto parts store. Some shops have cooling system power flush equipment but they typically charge $100+ for the service.
Click to expand...

Yeah, I want to contain this here at the house so the radiator flush sounds like a good option. However, since I have not yet pulled the head to change the head gasket, I really want to flush the entire system; and am concerned that if I start the engine with the flush, we will be pouring oil back into the coolant.

Thanks again.
 
I'd flush it after the repair.

Maybe a flush product isn't needed; might not water alone do the trick?

Fill the radiator with water, run it to temp, drain, and repeat until clean?

I never had this problem but that is what I'd probably do, once it has been repaired.
 
Mr. V said:
I'd flush it after the repair.

Maybe a flush product isn't needed; might not water alone do the trick?

Fill the radiator with water, run it to temp, drain, and repeat until clean?

I never had this problem but that is what I'd probably do, once it has been repaired.
Click to expand...

Thanks for the advice...my concern is the time that the sludge may harden, maybe oil and water will not harden...just thinking things through.

Cheers, RR
 
Disconnect the upper radiator hose and run your finger up along inside it. If it is a slimy oily mess embedded in the hose rubber, plan on replacing the cooling system hoses, at least the upper ones where the oil would migrate to. That stubborn oil film will degrade the hoses and you risk an early catastrophic meltdown.

Depending on how contaminated the cooling system components are, consider doing the what they are calling the "3 Day Power Flush" down near the bottom of this page:

http://www.sancarlosradiator.com/VoltageDrop/flush.htm
 
Why did the head gasket blow is kind of important, if it was because of the cooling system, that will really affect how you flush it out.

If it was my car, I would do the garden hose flush first. Then unhook the hoses from the heater core and hose that out, followed by blowing out with compressed air. If the radiator is still good, lay it flat and dump Simple Green in, slosh it around and rinse. You aren't getting it all out of the block so forget it. Fix head gasket and whatever blew it, then just change the antifreeze in a couple hundred miles.
 
I would remove the innards of the thermostat to allow constant flow, then fill the cooling system with white vinegar and water. Let it get warm, drain, repeat. It will take quite a few times but it'll come most of the way clean.
 
If you plan on doing a flush with a hose, make sure you turn the heat up all the way so you get flow through the heater core as well.
 
hiperfauto said:
If you have milkshake in your radiator chances are the transmission fluid heat exchanger in the radiator is bad. Do you have milkshake in the transmission?
Click to expand...

I agree with hyperfauto .... The problem is more likely in the transmission oil cooler inside the radiator.
I had the same exact problem on a 94 model 940, and the oil cooler was leaking.

You can check the oil cooler.
Unhook both oil lines from the transmission to the radiator.
Block the drivers side oil connection.......
I used a short piece of rubber hose that was a tight fix over the threaded connector on the radiator and clamped it with a hose clamp.
I inserted a bolt into the other end of the hose and clamped that to totally blocked one oil connection to the radiator.

With the cooling system completely full of water...and the coolant cap removed from the coolant reservoir,
I used low pressure air (10 PSI MAX) to pressurize the oil cooler inside the radiator.
I did this by using a rubber tip on my hand held air sprayer. I held it against tightly against the open oil connection and pushed air into the oil cooler.
With the coolant cap removed, air bubbles were coming out of the coolant reservoir.
This confirmed a leak in the oil cooler.

It's worth a check, and a heck of a lot easier than changing the head gasket.
 
Or take the radiator to a radiator shop for examination and repair, that is if you're lucky enough to have a radiator shop near you anymore.

They seem to be getting tough to find.
 
Last edited:
tintintin said:
Disconnect the upper radiator hose and run your finger up along inside it. If it is a slimy oily mess embedded in the hose rubber, plan on replacing the cooling system hoses, at least the upper ones where the oil would migrate to. That stubborn oil film will degrade the hoses and you risk an early catastrophic meltdown.

Depending on how contaminated the cooling system components are, consider doing the what they are calling the "3 Day Power Flush" down near the bottom of this page:

http://www.sancarlosradiator.com/VoltageDrop/flush.htm
Click to expand...

Thanks for the link...I definitely 'won't rush the flush!'
 
2turbotoys said:
Why did the head gasket blow is kind of important, if it was because of the cooling system, that will really affect how you flush it out.

If it was my car, I would do the garden hose flush first. Then unhook the hoses from the heater core and hose that out, followed by blowing out with compressed air. If the radiator is still good, lay it flat and dump Simple Green in, slosh it around and rinse. You aren't getting it all out of the block so forget it. Fix head gasket and whatever blew it, then just change the antifreeze in a couple hundred miles.
Click to expand...

Good advice, thanks again. RR
 
coalminer said:
I agree with hyperfauto .... The problem is more likely in the transmission oil cooler inside the radiator.
I had the same exact problem on a 94 model 940, and the oil cooler was leaking.

You can check the oil cooler.
Unhook both oil lines from the transmission to the radiator.
Block the drivers side oil connection.......
I used a short piece of rubber hose that was a tight fix over the threaded connector on the radiator and clamped it with a hose clamp.
I inserted a bolt into the other end of the hose and clamped that to totally blocked one oil connection to the radiator.

With the cooling system completely full of water...and the coolant cap removed from the coolant reservoir,
I used low pressure air (10 PSI MAX) to pressurize the oil cooler inside the radiator.
I did this by using a rubber tip on my hand held air sprayer. I held it against tightly against the open oil connection and pushed air into the oil cooler.
With the coolant cap removed, air bubbles were coming out of the coolant reservoir.
This confirmed a leak in the oil cooler.

It's worth a check, and a heck of a lot easier than changing the head gasket.
Click to expand...

The radiator is new, and I have new valve train parts plus VX cam here. This 740 is so clean, I am gonna take my time and get the engine fresh, make sure the head gasket is good, and enjoy it for a long time. I have sold too many good Volvos and this one is going to be my redemption for that. Cheers, RR
 
I've used some dawn dish soap mixed into the coolant (straight water) a few times (fill/drain/fill/drain). I run the engine for 10 minutes or so then drain/fill. I usually do this without a thermostat in place and the heater control set to hot. Makes a foamy mess but the soap is pretty effective at cleaning out the oil and junk. I'm always surprised at what comes out. The dish soap is very gentle on gaskets and such. The last time I usually pull the upper radiator hose off the radiator and stick a hose in the radiator neck to make up while it barfs out the hose to clear out the rest of the soap. with the thermostat removed, you can also just push water through the block with a garden hose.

I then refill with antifreeze and distilled :-)poo:) water.
 
RR said:
Thanks for the advice...my concern is the time that the sludge may harden, maybe oil and water will not harden...just thinking things through.

Cheers, RR
Click to expand...

And anti-freeze isn't going to play well with your bearings long term I don't believe.
 
I fought milkshake in my brothers e30 for a while after a head gasket replacement. They sell coolant flush but we also used dish soap as its a natural degreaser. Luckily the volvo cooling system is less ****idy then BMW made their's
 
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