: Heat Exchanger Elimination



guardian
02-22-06, 01:34 AM
I have referred to seeing this writeup in earlier posts here. I had seen the writeup weeks ago on the net, then was unable again to locate it.

Now a thoughtful poster over at the Yahoo Catera forum has very kindly posted this URL

http://groups.yahoo.com/group/CateraOwners/files/External%20Oil%20Cooler%20Install.doc

from which you can download the writeup.

This is not my writeup, I have not performed this procedure myself personally, and I cannot vouch for the specifics and the details. But, in general at least, it makes sense to me. It is a way to eliminate completely the factory heat exchanger which can fail and cause intermixing of engine oil and coolant.

Also use of such an oil cooler as this will, in effect, increase the overall cooling capacity of your Catera. It is because this oil cooler moves heat from your engine oil directly to passing air, which removes heat from the system straightaway.

When heat from the oil is moved instead to the coolant, as happens with the standard Catera heat exchanger, the heat remains within the system, awaiting removal ultimately by the main radiator.

So installation of this oil cooler provides "another way out" for a portion of the heat created within your engine system. This reduces the load on, the heat input into, the main cooling system.

ewill3rd
02-22-06, 08:22 AM
I have never seen one of these oil coolers fail in the manner you mentioned. The cover plate usually leaks coolant out of the engine.
I am sure the engineers at least thought that the medium of transferring the heat from the oil to the cooling system and then to the atmosphere was probably a good idea.
In fact in cold weather situations I can see the "heat exchanger" actually helping keep the engine lubed better by warming the oil to an even temperature, rather than using an air cooler to keep the oil colder.

I didn't read the methodology since you have to log in to yahoo to access that page, I am sure it's a viable procedure if you want an alternative to the factory setup.

It's like the old addage... "just because you can do something, doesn't mean you SHOULD do it".

My $.02.

guardian
02-22-06, 09:46 AM
I have never seen one of these oil coolers fail in the manner you mentioned. The cover plate usually leaks coolant out of the engine.

Your input _much_ appreciated. Thanks

First let me stipulate to the fact that Catera heat exchangers are more often referred to as oil coolers. After all they do cool the oil by moving heat from the oil into the coolant. But the term "heat exchanger" is also used and I use it because it seems, to me at least, more descriptive of function. I tend to focus in my mind on the exchange.

Anyway and regardless, I have seen multiple Catera reports of oil in the coolant, or vice versa, I cannot recall . . . . perhaps both as there is intermixing. Was the heat exchanger improved, upgraded, somewhere along the line, eliminating this problem? I do not know. Perhaps another visitor here will be able to enlighten us.

But your comment about the cover plate leaking coolant out of the engine has really got my attention. This is not something on Catera I have seen mentioned previously, and I am very keen to learn more detail.

Full disclosure: I do not even know or understand what you mean by "cover plate". Any further detail/explanation would certainly be of great interest. Is this something you have witnessed frequently on Catera? Are you aware of engines having been damaged by this failure?

Any further detail you can provide will be helpful and interesting. Thanks.

I also think you raised good points re summer vs. winter on the oil cooler. I confess to being more focused on warm weather concerns, and what I wrote earlier had that slant. But I agree with you that in winter it is well to get oil up to running temperature without delay, in order properly to lubricate the engine. Of course some such concerns can be addressed by running the proper oil for conditions, especially if conditions are extremely cold.

But I think your larger point, an excellent one, is a focus on the role of the engine thermostat, and the way its setting reflects back into heat exchanger operation. I agree that the amount of heat extracted from the oil is a function of the temperature delta at the exchanger. It is a really good point, and not one I had considered. Even now that you have pointed it out to me, I cannot claim fully to be able to wrap my head around the engineering involved.

Certainly oil coolers that exchange heat directly to air are common in automobiles. They are used to cool both engine oil and transmission oil. In my earlier writing I was sort of going with that paradigm.

But your point about there possibly being a more subtle reason for use of a heat exchanger is intrigueing. I hope another poster here will chime in with an opinion.

ewill3rd
02-22-06, 10:54 AM
To clarify, I meant that I personally have never seen it on a Catera. Of course that is not by any means to say that it has never happened nor could it. I just meant to say that it's not a "common" problem albeit a definite possibility.
Sometimes the direction of the intermix depends on the pressure in each system. The oil should be the winner since the oil pressure is regulated higher than the pressure in the cooling system, as long as the engine is running anyway.
Once it's shut off the cooling system pressure would in such a case push the coolant into the oil and from there bad things would happen.

The heat exchanger/oil cooler is mounted with two nuts to a plate and placed in what would be the lifter valley on an OHV engine. Usually you would use an RTV type seal to seal this plate to the block.
I posted some images a few weeks ago of what this looks like. I might be able to get some real photos of the setup as we do them here fairly often.
Typically what happens is you'll see a large coolant leak from the rear of the engine block. The sealant at the plate fails and coolant just passes on out. Also back there is the water control valve which can also fail so if you get a leak in this area it should be checked thoroughly before any parts are replaced. I have seen both misdiagnosed as the other.
The failure in this case would just be that of a system with low coolant.

I am glad you understood that I was just trying to raise some points in my post. I don't know from a scientific standpoint if it's a good idea or not, but I would just have some reservations about re-engineering most any system that has to do with the oiling and cooling on a car.
That is all I wanted to get accross. Most people do think of summer driving almost exclusively in my experience.
Just want to end by saying thanks for your well worded reply.
:D