Clear Condensate Under Oil Cap

[Matahoe]

Hello. I have a 2005 Tahoe with 5.3T engine. I have what I believe is the infamous missing coolant issue. Coolant recovery canister always empties over time. I have to keep adding 50/50 Dexcool to fill canister to the halfway point. I also can't find any drips or smell of coolant exterior to the vehicle anywhere. Been trying to wait it out and hope that it would grow to a visible leak. At times it seems I have more steam coming out the tailpipe but it definitely isn't smoke. I do get a weird smell...kind of sweet but definitely not raw coolant burning smell. This has been happening over the past year since I have owned to Tahoe.

Well today I was going to add the ACDelco UV Dexcool dye into the system but I found something else I think might be a smoking gun...

I was checking the oil and decided to remove the oil cap just to see if there was anything milky. I didn't see anything striking except for some clear watery condensation drops on the underside of the oil cap. Knowing I had no chemical kit to test the composition of the liquid I decided to swipe some on my finger and taste it on the tip of my tongue. I thought it would be tasteless and like water. Come to find out it had the exact numbing/sweet flavor of coolant.

Can anyone tell me what might be the problem here? I have done some preliminary searches on Google but all I come up with is people who have milky white stuff under their oil cap, not what I have which is a clear Dexcool tasting liquid. Assuming this is coolant from the infamous leak I don't have any other indication. I took the valve covers off this past summer but never saw any milky oil and water goopy mix under there. I also spoke with a nice service rep at the local Chevy dealership and he said that he has seen the Castech head issue and sometimes you wont see it leak unless you are really up close. So now I am at the point where I might need to remove my valve covers again to check the for the Castech logo. Is this how I should proceed further?

 

[retiredsparky]

You have cracked heads, most likely Castech. The only way you have coolant on that cap is through small cracks often around the head bolts. Your symptoms are indicative of vaporizing of the coolant and it condensing on a cooler surface. The amount of coolant is so little at this time, the oil doesn't get milky. The steam in the exhaust will vary due to exhaust temp, varying size of each crack depending on head temperature. Yes you are on the right track-these heads are junk.

Research new heads. Don't keep driving this vehicle--the coolant will cause damage to cam bearings, etc. Summit racing, Rockauto.com etc.

Avoid Castech heads. You have many choices. I have seen these symptoms on several vehicles that I have repaired for friends. If you wait long enough, you will need a cam like one of my friends needed.

Yes, you could have early head gasket failure--so remove the heads and inspect. If you have Castech heads, do you really want to replace the gaskets, but not those heads with new head bolts freshly torqued. I would not. The risk would be that the poorly designed and manufactured Castech heads could fail with the new stresses on them.

Larry

 

[Matahoe]

Thank you for your input sparky!

Would sending in a Blackstone oil sample be of any additional benefit? They test for trace amounts of antifreeze in the oil. This, and checking for the Castech logo would be the preverbial nail in the coffin if you will. What say you guys? Any other tips before I order some heads/gaskets?

 

[retiredsparky]

Blackstone does good work, very accurate testing, will email you the results, with comments. Tell them your concerns when you call to order the test kit. On another note, they also test tranny fluid

 

[Matahoe]

Update: Since my last post I added K&W FiberLock Head Gasket and block Repair to the coolant. It seems to be working very well. I haven't seen the coolant go down in the recovery reservoir at all. Level is just over half. As,a result I no longer get any whif of coolant under the hood like I used to. I never could see any external leaks.

As for the oil analysis. About a month ago I got the results back from Blackstone. Here is what they said... let me know what you think.

"Matt. You suspected coolant to be an issue, and that's definitely the case. We found high amounts of potassium, silicon, and sodium which show coolant contamination. Silicon could also be abrasive dirt, so check the air intake for leaks or cracks just to be safe. The coolant is causing excess wear. Iron is from steel parts, probably rotating shafts since we've got lead from the bearings. The bearing area is traditionally what coolant affects first. It's hard to say where the leak is. Have you done a pressure test yet? Keep oil changes on the short side until you find the leak."

 

[rockola1971]

Sure sounds like a cracked head, blown head gasket or cracked block. Pull the valve covers off and check the logos on the heads. There are head pics all over the net on what to look for and where on the head.