Cleaning out the oil cooler between engine builds


Active Member
Dec 9, 2004
I recently rebuilt my engine, 3.8L 109 block. It had spun a bearing and had camshaft material missing on two lobes.

The engine builder told me to clean out the oil cooler by pouring lacquer thinner in it, let it sit for 5min and then blow it out using compressed air.

Is this a sound procedure? Is it necessary? How many have done this to prevent re-contamination? Thanks.
FORGET that..

idea. The coolers have "turbulators" in the tubes. The crud WILL hang in these crevices, and come to haunt you later.:eek:
The correct way is to:
A. Disconnect the cooler, and replumb to an external cooler.
B. Have the OEM cooler replaced, by having the old cooler removed from the rad tank.
I put my own version of the "turbosaver" behind the rt headlite, on the rad support. I added a screened opening in the rt side air dam. I then mounted, and plumbed an external cooler.NOT cheap, but it was pretty much foolproof. If I did have an engine go "tango uniform", I could throw the cooler away, and keep the system clean.:cool:
I contacted a radiator shop and they told me that they could clean it by filling it with solvent. Similar to what I could do on my own. Is replacing the oil cooler w/ an external one the only solution? I would need more witnesses to employ that fix.
Has any one cleaned their oil cooler the one inside the radiator?
The only way to clean it out is to buy a new one. Why take a chance after you spent X$$$$ to fix the motor and have it do it again.
I agree. Don't even think about cleaning out the OEM oil cooler. Go with an external aftermarket oil cooler! Don't risk wiping out your new motor or turbo.
I've cleaned it out, and it didn't seem to come back and bite me in the butt. I didn't do it with solvent and compressed air, I did it with engine degreaser I think and water. In the end I used a garden hose to force water through it,in both directions, and caught samples in a clear jar. When I caught several samples in a row that had no bits in them (again in both directions), I called it clean. Blew it out, poured some rubbing alcohol through it and blew it out again (trying to get it totally water free), a little WD-40 in there...

Now would I recommend this to someone? No, way too much risk of getting blamed if there is a problem later. But, for me, it was a risk I was willing to take. Any oil that goes through the cooler has to go through the oil filter. I trusted my filter (remote mount "turbo saver") to catch anything that might have gotten left behind. Maybe that trust was misplaced, but again, I seem to have gotten away with it.

I'd say replace the cooler in the rad, it's not that expensive to have the tank taken off and a new cooler installed. Probably as cheap or cheaper than routing lines to a new external cooler.

It has been a long time. In your case, you knew how the oiling system works and you knew that you had a back-up with the remote oil filter. It pays to know what you are doing and you do. Glad it worked for you.
Replace its the cheapist money you will spend. $100 or take engine out and fix bearings again
It cannot be flushed IMHO.

Also not really required IMHO.

I no longer run one and did not see significant oil temp increase (Sender in the pan)

Lots of people said a cooler is a must, but no one else had oil temp guages.

I rarely see over 200 degrees.

I will put one in before I run the Silver State Challenge :biggrin: :biggrin:
I took the radiator out and took to a very good shop, The head guy told me that he could clean it, but there is no way that he could get all of the metal flakes out of the cooler. So, we discussed replacing the OEM cooler and the cooler would run appox. $70 and the labor $60 which is $130. So that leads to two options. 1. Replace my entire radiator with an stock replacement with all the correct trans, oil, water coolers in the stock positions, which I am not sure is even available. 2. Purchase an external oil cooler.

Please provide some choices for an external oil cooler that the stock hardware will fit, and the mounting location that you chose. I have a large trans cooler right under the radiator already, and I am afraid that I will not be able to find suitable spot to mount the external oil cooler.

Also, if you know of a really good radiator replacement that has all the stock setup please list it.

Thanks to all
...Also, if you know of a really good radiator replacement that has all the stock setup please list it...
GM # 88959435 (Delco 20269) is the updated, original style brass/copper radiator. It has the stock engine oil & tranny coolers in the correct location.

It's Expensive: List $445 , but can be mail-ordered for about $300 + S/H.

Another option is the all-aluminum radiator from GBodyParts with correct, built-in oil & trans cooler ... about $450.
pts is running a free shipping special on their "bolt in" aluminum radiator with both coolers in the stock location, $499.
Why does everyone think they NEED an oil cooler? I haven't ran one since 2002 in my car. Ditch the stock radiatior, it is crap anyways, and get yourself a nice aftermarket aluminum radiator. NEVER run a new motor with a used oil cooler! I've seen so many turbo failures and motor failures for that matter because people re-used a stupid oil cooler. It is NOT needed period! If you run a 160 thermostat in the car, the engine coolant runs so cool to begin with, that it actually cools the oil at the same temperature.
In fact, if you really want to do your tranny a favor, get a standalone cooler, mount it under the front of the car with it's OWN cooling lines coming straight from the tranny, and put a small electric fan on the cooler, and that tranny will run very cool all the time. Why run hot fluid through a HOT radiator? That doesn't cool anything...a radiator is meant to cool WATER and nothing else!
...Why run hot fluid through a HOT radiator? That doesn't cool anything...a radiator is meant to cool WATER and nothing else!
Because fluid-to-fluid heat exchangers are much more efficient than air-to-fluid, and can reduce temp of hot tranny fluid very rapidly to the rad temp (160-180º).

Eg, compare how quickly a broiling hot pan takes to cool if left in free-air, versus placing pan in hot water ... it very quickly reaches the temp of the hot water, which is cooler than pan started.

Every GM towing package I have seen, first runs tranny fluid thru the radiator and then runs fluid thru the external air cooler ... the rad cooler removes much (if not most) of the heat from fluid.

many posts this subject, eg,
good points...but for what we use our cars for, we really don't need an oil cooler for one. The only people that really need oil coolers are those who autocross or run circle track where they are constantly beating on the engine. Also we don't tow large loads with our trannies like trucks, thus they don't generate as much heat as we think they do. Air to liquid coolers work just fine for what we do. But hey...this is just my thinking and preference, so don't take it to heart if I say something. I'm just going off of experience and what has worked for me and many others.

But I do know one not run the same oil cooler on a new motor! when I worked at PTE, I constantly got calls about people's turbos failing minutes after they installed it on the car. The FIRST thing I would always ask them is "is this a new motor?" "are you breaking it in for the first time?" "are you re-using the old oil cooler/radiator setup?" they would say yes and I would say yup that's what I thought...when the old motor failed, it left crap in the cooler and that crap got in the new motor and ruined the new turbo.
We agree on the main point, Don, namely that it's best if coolers are replaced or bypassed , if there has been any chance of "shrapnel" getting inside the cooler.
Yes I am convinced. I would not run the old oil cooler even if you paid me. I want this engine to last at least a couple of years.

I have not done a search, but I read the forums quite a bit and I have never read a thread on oil cooler replacement. I bet there is a considerable amount of people that reuse their old oil cooler.

I am looking to replace the oil cooler at this point, I would like to replace the entire radiator, like suggested, but I am limited on funds for just sinking money into the rebuild. I am trying to look on the major racing parts suppliers and find a good oil cooler that will fit the stock hardware any suggestions?
I am just getting ready to drop my motor off to be rebuilt also,i was thinking off running an external cooler,but after reading this,is it a waste of money or really needed?I definately wont be reusing the stock oil cooler.And does anyone have any recommendations on what cooler to use?