90zxdriver Posted June 11, 2015 Report Share Posted June 11, 2015 I hate to have to start this post. About a month ago I noticed a small (6") puddle under the truck just behind the passenger front wheel that looked and smelled like GM's Dexcool but had more of an oil consistency, it was thicker than coolant and darker in color. I checked the coolant tank and it was full. I traced the leak to the coolant overflow hose from the overflow reservoir. I cleaned up the mess and kept an eye on it. The truck never runs hot, always stays right in the middle of the gauge. She isn't overheating either. The coolant has 40k miles on it and about time to be changed anyway. I didn't ignore the problem because these things obviously don't fix them selves. However, it had not leaked again. Then I had a issue with my transmission being low on fluid and slipping. Took it to the tranny shop and they could find no visible leak but obviously it was down fluid. I had the trans serviced and all was well, no more slipping but still no explanation as to where the trans fluid went. They said bring it back in a few weeks and they will put it on the lift to see if there is anything wet under the truck. Then we fast forward to tonight! I went up to Lowes and noticed the transmission acting funny. Not slipping, sloppy would be the best way to describe it. *note* this is how it was acting just before it started slipping. So I get home, bring my stupp into the house and about an hour later when I go back to the garage, huge puddle once again behind the passenger wheel. Again, smells like coolant but much darker and thicker. Again, trance it back the coolant overflow hose. You can see where it is running down the inside of the passenger fender to the ground. The coolant overflow tank is once again full with a nasty brown sludge. I immediately think the head gasket and check the engine oil but looks normal. Nothing milky or foamy/bubbly. Just looks like normal engine oil and is at the correct level. I then check the trans fluid and guess what, its low again. Crawl under the truck and can't find anywhere on the transmission that is wet. I'm not an overly smart person and a bit overhead when it comes to engines but I have a basic understanding. So, it appears my transmission fluid is somehow mixing with my coolant. The only logical place I can think this could occur would possibly be the radiator. Does this sound possible? It would explain the mystery of where my missing transmission fluid went as well as why the coolant tank is overflowing since it is obviously a closed system and the level should not be changing. Quote Link to comment Share on other sites More sharing options...
90zxdriver Posted June 11, 2015 Author Report Share Posted June 11, 2015 Quote Link to comment Share on other sites More sharing options...
90zxdriver Posted June 11, 2015 Author Report Share Posted June 11, 2015 Quote Link to comment Share on other sites More sharing options...
90zxdriver Posted June 11, 2015 Author Report Share Posted June 11, 2015 Quote Link to comment Share on other sites More sharing options...
BlueAKSSS Posted June 11, 2015 Report Share Posted June 11, 2015 Yikes, don't like to see threads like this! I think you have come to the right conclusion, somehow the internal transmission cooler in your radiator must be leaking into the coolant. Not a good situation! I would get a new radiator installed and have both the transmission and cooling systems cleaned out/flushed. If your good with comfortable working on it the radiator is really easy to change with basic hand tools, drain pans, ect. Hope you can get that solved qucikly and I would not recommend driving anywhere with it like that to prevent transmission damage. Quote Link to comment Share on other sites More sharing options...
canadianVRss Posted June 11, 2015 Report Share Posted June 11, 2015 I also agree with your prognosis. Looks like Trans fluid in your coolant system entering via the internal Trans cooler. Quote Link to comment Share on other sites More sharing options...
90zxdriver Posted June 11, 2015 Author Report Share Posted June 11, 2015 I just wasted $300 two weeks ago having the transmission serviced. This truck is really trying my patience!!! Quote Link to comment Share on other sites More sharing options...
evandostert Posted June 12, 2015 Report Share Posted June 12, 2015 It happens. Radiators are fairly cheap anyways on this truck. Quote Link to comment Share on other sites More sharing options...
abss_2003 Posted June 12, 2015 Report Share Posted June 12, 2015 Man your going to have to flush the engine cooling system a sh*t load of times too. Quote Link to comment Share on other sites More sharing options...
BC DOORMAN Posted June 12, 2015 Report Share Posted June 12, 2015 Yes I have read of the internal trans. cooler leaking in the radiator. Also, while you are spending time and money, get a tru cool 40 K trans cooler. That way you can bypass the radiator cooler so this never happens again. I picked one up with out the thermal bypass for $160.00 and it is a great piece! So just use that as your trans. cooler I also run that same cooler on my 2500 'burb tow vehicle. No issues. Of course you will be busy flushing the coolant system, the trans., and your new radiator. Make sure to plug the trans. cooler inlet/ outlet on your new rad. also. If the same leak ever occurs again your coolant will at least be contained. Best of luck, enjoy the wrenching Quote Link to comment Share on other sites More sharing options...
90zxdriver Posted June 16, 2015 Author Report Share Posted June 16, 2015 Any problem going with another GM radiator or is there something better out there? Quote Link to comment Share on other sites More sharing options...
EXGM Posted June 16, 2015 Report Share Posted June 16, 2015 Any problem going with another GM radiator or is there something better out there?If it was mine that's what I would use. I am not aware of a aftermarket high performance rad for Silverados. So you would then be looking at a custom built one for high bucks. Any of the aftermarket ones you pick up will be of cheaper quality. If you plan to keep for a while buy OE if your going to turn n burn truck buy a cheap am one..... Quote Link to comment Share on other sites More sharing options...
evandostert Posted June 23, 2015 Report Share Posted June 23, 2015 Flex-a-lite makes a sweet set up seperate rad and trany coolers too. Quote Link to comment Share on other sites More sharing options...
1BAD2K Posted June 23, 2015 Report Share Posted June 23, 2015 Just get a gm radiator and a trucool 40k trans cooler and do not run the trans fluid through the new radiator. Change fluid in trans, run a cooling system flush and Yu should be good. Annoying but not a huge problem imo. Quote Link to comment Share on other sites More sharing options...
Tim713 Posted December 17, 2019 Report Share Posted December 17, 2019 F I think I have the same thing going on with mine now... thanks for a great database here guys. Quote Link to comment Share on other sites More sharing options...
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