Ls swap issue

[Brady Clendenning]

Hey everyone,I’m a mechanically inclined individual who has recently LS swapped my s10. I’m having a issue with it, and I’m wondering if I can get some insight.

Here is a quick run down. 92 s10, 2001 5.3 gen3 swapped with a wrecking yard motor (562 heads) . Was told it had good compression. Runs great, drives great, does not overheat. Everything about the cooling system is new. Rad, hoses, waterpump and stock temp t-stat. Electric fans. 3 wire f body sensor ran to front head. Verified proper temps with gauge and scanner. Steam port attaches directly to radiator. Running a overflow tank (bottom feed) to rad cap.not a expansion tank.

Issue- I’m not overheating, oil is fine, coolant is fine, no fumes/white smoke from exhaust. I’ve stopped up my rad, right to the neck, run it and I get bubbles from rad, to overflow. It’s not BOILING. Just air bubbles. System was properly burped. If I fill my rad up to the neck, it will bubble and dump about a quart into my overflow, and not return to rad. It will not dump anymore coolant than that,unless I refill. It will never return from overflow, but no matter what, the bubbling is always there. It’s not a steady rapid bubble. But its consistent bubbling.

I’m not a mechanic, but have seen a few different head gasket failures. Usually a oil/coolant mix, overheating, clouds of anti freeze out of exhaust. I’m not experiencing any of that. It’s like exhaust fumes are entering the cooling system, but coolant is not entering the combustion chamber. I’m leaning towards a H.G. but it just seems odd to me.. am I missing something. Being a pressurized system, usually stuff would leak out, but since the combustion chamber has so much pressure, its finding it’s way in obv.? So either air is in the system still, or air is entering, and I dont know any other way it could enter. Before I tear into this thing, is there anything else anyone could think of that I can check, diagnose? I’ve had a few friends look at it, some say run it, unless it overheats I shouldnt worry.

Thoughts, ideas?

• This topic was modified 4 years ago by Brady Clendenning.
• This topic was modified 4 years ago by Brady Clendenning.

Topic

[Richard Kirshy]

Suggest you first try a combustion gas test to see if you truly have a leak somewhere between the combustion chamber(s) and water jacket.
Might also try a new radiator cap.

[Brady Clendenning]

Thanks Richard Kirshy, I’ll look into doing that. It does have a new radiator cap. That was the first thing I thought it could be. I also had it running with rad cap off, and it was bubbling though, so air is entering from somewhere past the cap. Thank you.

• This reply was modified 4 years ago by Brady Clendenning.

[Brady Clendenning]

Thanks Richard Kirshy, I’ll look into doing that. It does have a new radiator cap. That was the first thing I thought it could be. I also had it running with rad cap off, and it was bubbling though, so air is entering from somewhere past the cap. Thank you. Edited to reply. New to forums.

[Richard Kirshy]

Just remember a part being new doesn’t always mean it’s good.

[Author]

Replies