Oil Cooler and Head Gasket Questions

[nick]

I've noticed that my 1983 760 GLE has coolant lines running from the back of the head, down to an oil cooler or something near the oil filter and then back to the thermostat housing.

Is this oil cooler serving a purpose if the motor is never under a heavy load? I don't run this car hard...at all. I typically get above 37 mpg. On my last tank I got 38.5 mpg.

I'm think that I have a blown head gasket between a coolant passage and the combustion chamber. There are no externally visible coolant leaks and no oil contamination. A cloud of steam exits my tailpipe when I leave traffic lights and when accelerating on the interstate. It drinks about a gallon of water/antifreeze every 200 miles.

If it's the Lord's will, I'm planning on replacing the head gasket on Friday. I figured that I'd go ahead and bypass this oil cooler while I was at it. Any suggestions or other things to consider?

Nick

[v8volvo]

I would leave the cooler alone and in place. If you ran the car hard, then I would suggest replacing it with a true dedicated oil-to-air exchanger and sandwich plate, but if you are really easy on it, then it is still doing you some good because it helps the oil get up to temp quicker (transfers coolant heat into oil). Warm oil is a good thing, especially in engines that don't get worked hard.

It's also good to have it there for those rare times when even someone who is normally very easy on the motor decides to get into it and have a little fun. What's the point of having a sweet, high-revving turbodiesel six when you can't enjoy it every now and then? Whenever you get above a certain RPM (and oil pressure), your piston cooling jets come into play to shoot oil up underneath the pistons for cooling under load. When that happens, it brings a lot of extra heat into the engine oil, and it's the cooler's job to be there and absorb it. It is good for any engine to get worked hard every now and then (assuming it's warmed up and in basically good shape), and especially important on a diesel.

There is an easy test to do to know if you have a HG issue. Usually on these engines HG issues show up as either no heat out of the heater in the car, or as an overheating problem. Rarely do you see them lose coolant -- they overpressurize the system, and usually the only way they lose coolant is if that causes a hose to blow. I'm not convinced your HG is the reason for your coolant loss, though it could be.

Here's the head gasket failure test: with the engine off, detach the small coolant return hose that runs from the top right (passenger) side of the radiator to the coolant expansion tank on the RH strut tower. Detach it at the expansion tank, then stick the end of the hose you just disconnected into a clear jar filled with water. Hold your finger over the exposed nipple on the expansion tank where the hose used to be so that the system is sealed everywhere except for the hose that's stuck in the jar of water. Have an assistant start the engine and spend about a minute watching what happens. If you see a steady stream of air bubbles coming out of the end of that hose that's submerged in the jar, then you have a head gasket problem. If you don't see any bubbles, or you just see a few when it first starts but then don't see any more, then your HG is probably fine and you have an issue elsewhere. The water pump O-ring seal can often get old and brittle over time and I've seen them leak from there. The leak can be hard to find.

What kind of reservoir cap are you running -- a 75, 100, or 150 kPa?

Planning on doing a new timing belt if you pull the head?

[v8volvo]

I would leave the cooler alone and in place. If you ran the car hard, then I would suggest replacing it with a true dedicated oil-to-air exchanger and sandwich plate, but if you are really easy on it, then it is still doing you some good because it helps the oil get up to temp quicker (transfers coolant heat into oil). Warm oil is a good thing, especially in engines that don't get worked hard.

It's also good to have it there for those rare times when even someone who is normally very easy on the motor decides to get into it and have a little fun. What's the point of having a sweet, high-revving turbodiesel six when you can't enjoy it every now and then? Whenever you get above a certain RPM (and oil pressure), your piston cooling jets come into play to shoot oil up underneath the pistons for cooling under load. When that happens, it brings a lot of extra heat into the engine oil, and it's the cooler's job to be there and absorb it. It is good for any engine to get worked hard every now and then (assuming it's warmed up and in basically good shape), and especially important on a diesel.

There is an easy test to do to know if you have a HG issue. Usually on these engines HG issues show up as either no heat out of the heater in the car, or as an overheating problem. Rarely do you see them lose coolant -- they overpressurize the system, and usually the only way they lose coolant is if that causes a hose to blow. I'm not convinced your HG is the reason for your coolant loss, though it could be.

Here's the head gasket failure test: with the engine off, detach the small coolant return hose that runs from the top right (passenger) side of the radiator to the coolant expansion tank on the RH strut tower. Detach it at the expansion tank, then stick the end of the hose you just disconnected into a clear jar filled with water. Hold your finger over the exposed nipple on the expansion tank where the hose used to be so that the system is sealed everywhere except for the hose that's stuck in the jar of water. Have an assistant start the engine and spend about a minute watching what happens. If you see a steady stream of air bubbles coming out of the end of that hose that's submerged in the jar, then you have a head gasket problem. If you don't see any bubbles, or you just see a few when it first starts but then don't see any more, then your HG is probably fine and you have an issue elsewhere. The water pump O-ring seal can often get old and brittle over time and I've seen them leak from there. The leak can be hard to find.

What kind of reservoir cap are you running -- a 75, 100, or 150 kPa?

Planning on doing a new timing belt if you pull the head?

[nick]

Thanks for the great information!

Its good to know that I might not have a blown head gasket. I don't understand how a 15 psi cooling system could force it's way into a ~500psi combustion chamber, I just figured that the coolant entered he combustion chamber during the intake stroke.

I was definitely planning on replacing the timing belt during this job, thanks for checking.

I have the 100 kpa cap.

You think that I could be leaking all that water via water pump o-ring? It seems like the leak would be visible. I will definitely inspect/replace this oring before pulling the head. An observation that points to this o-ring failing is that the cloud of steam I see typically spans the full width of my car. I would expect the cloud to be considerably narrower and to be localized to the tailpipe side of the vehicle if it was a coolant going through the combustion process.

[nick]

My motor failed the head gasket test per your instructions. I replaced the head gasket, timing belts, and timing idler pulley this weekend. I also rebuilt all the injectors and the engine wiring harness! It was a great weekend, for sure!

The car definitely idles much smoother now compared to how it used to. I now have a noticeable whine gets louder with increased RPM. Do you think it could be the new timing belt idler pulley? Have you ever had new timing belts induce a whine if over tightened? I set the belts at 13.5-14.0 units.

Before


After

[nick]

I set the timing to 0.97 using the method described here: http://www.d24t.com/showpost.php?p=968&postcount=3

It wasn't bad at all:
1. Set motor to TDC
2. Install & tension injection pump belt onto free-spinning camshaft sprocket
3. Rotate pump to proper time
4. Tighten cam sprocket
5. Verify timing after full revolution

This forum is a great resource!

[ngoma]

Those injectors look sharp! How did you get them so clean? Did you use new nozzles? What did you set the breaking pressure to? You are a fast worker. Mine took me several days to get them cleaned up and set up.

[nick]

After disassembly, I place them in an ultrasonic cleaner for about 3 hrs, then I took a wire wheel to each one of them. I didn't have any shims laying around to set the cracking pressure, so I just distributed the shims among the injectors evenly. The shim thickness ended up being around 3/16 in for each injector.

Have any of you ever experienced a whine coming from the front of your motor after an timing belt idler pulley replacement? If I can't isolate the source of the sound I'm probably going to disassemble the old pulley and press in a new bearing, then replace the "new" pulley with it.

[nick]

After disassembly, I place them in an ultrasonic cleaner for about 3 hrs, then I took a wire wheel to each one of them. I didn't have any shims laying around to set the cracking pressure, so I just distributed the shims among the injectors evenly. The shim thickness ended up being around 3/16 in for each injector.

Have any of you ever experienced a whine coming from the front of your motor after an timing belt idler pulley replacement? If I can't isolate the source of the sound I'm probably going to disassemble the old pulley and press in a new bearing, then replace the "new" pulley with it.

[nick]

After disassembly, I place them in an ultrasonic cleaner for about 3 hrs, then I took a wire wheel to each one of them. I didn't have any shims laying around to set the cracking pressure, so I just distributed the shims among the injectors evenly. The shim thickness ended up being around 3/16 in for each injector.

Have any of you ever experienced a whine coming from the front of your motor after an timing belt idler pulley replacement? If I can't isolate the source of the sound I'm probably going to disassemble the old pulley and press in a new bearing, then replace the "new" pulley with it.