5.3 LM7 turbo. Stock untouched short block, summit 8719 cam, single turbo. Stock catech heads that were cleaned up on the sealing surface. I'm running stock MLS ebay gaskets and speedmaster head studs and stock rear steam block offs and stock fronts run to the back of the LS3 Camaro Water pump. 160*F Lingfeilder Tstat for LS3 pump and a entrophy dual 1" core aluminum radiator with a SPAL brushless 500w fan and shroud (100% coverage). I had rust issues inside the cooling passages in the block which I used evaporust but this was before I went turbo. Full disclosure... I had the heads torqued down but removed them to clean the cooling passages and I just reused the gaskets (engine was never run) and retorqued the head studs to 65ftlbs.(this was a few years ago). The engine was run with a champion radiator and had no issues, nothing in the cooling system. I then swapped to a brushless fan and entrophy radiator as I wanted better fan control and cooling, then I went turbo. I have always run the trans cooler in the radiator and then an external cooler (stalled auto).

My radiator gets this weird green foam in it... looks like if oil was mixing with coolant but its just a layer on top of the coolant and not mixing in with the coolant. Think foam floating on top of the coolant which is basically clean. Also my coolant level drops a few inches in the radiator after I drive. Doesn't seem to be going to the overflow tank. All started after the turbo swap, mind wants to assume its leaking under boost but I haven't been able to confirm. I did pressure test the cooling system (17psi and left it for 12hours and no leaks). Now it seems that my idle temps are rising at 1*F every 3-5s which does away as soon as I give it alittle RPM. Driving with rpms above idle the temps are 175-178*F, if I coast at idle rpm temps will slowly go up, at a light at idle temps slowly go up and I've been as high as 196*F which it would never get to before at idle in the summer (its now 50*F out). I have checked the oil dipstick and pulled the valve covers and have not found any coolant in the oil. I did a trans cooler swap like 3 months ago and found NO coolant in the trans circuit. I haven't been able to rest for exhaust gases in the radiator with my tester I have due to the angle of the rad cap. Something is obviously up if I'm loosing coolant and getting green foam. I'll attach some pics of the foam but I guess now the cooling is being affected at idle which it never did so I need to figure this out. Car has only been out a few times (100 miles maybe total) and it took 20-30oz of fluid last night. My steam vents are basically level with the radiator cap... makes me think I need a expansion tank to push the cap up higher.

I've tried flushing the cooling system with hose water and used a super cleaner as well as thermocure to remove any rust in cooling system (including pulling the block plugs). Due to my setup, (heater ports plugged in WP) its not easy for me to flush the system and run the engine. I run FRAM concentrate yellow/green all model coolant and distilled water as its the cheapest stuff I can find at the local stores.

The breakdown:

• Green Foam floating on coolant - coolant is otherwise fine.
• Drop in coolant - holds 17psi not on ground or in overflow tank that I can tell.
• No coolant in the trans circuit or engine oil
• no visible coolant leaks when pulling the valve covers.
• Can't tell if I'm burning coolant in boost?
• Don't think the combustion tester will find anything as it doesn't seem to be pressurizing the radiator.
• Front steam ports are basically at the same level as the radiator cap
• Cooling fan is working, Tstat seems to be working
• Needs more RPM than idle to keep engine cool and temps drop fast.
• 
  

 

Well the first thing id point out is that ls water pumps need looped, not plugged when deleting a heater.

 

Ive heard the exact opposite. Also This has always been like this for years and never had this issue. I also have another car where I plugged both heater ports and no issues.

 

FYI, this guy is saying the exact opposite of what your saying and how I have it. Looping mixes the hot and cold side of the cooling system resulting in contaminated coolant and overheating.

 

By the look of your radiator cap you have oil in your coolant, maybe leaking after using old head gasket

 

I had this happen to me once with an LY6. I was torquing headbolts after a sloppy rebuild (new rings and bearings and a quick ball hone) when I heard a pop from the block a thousandth of a second before the torque wrench clicked. I paused…I knew what I heard, but was in disbelief because everything I THOUGHT was clean. Upon teardown I found I used too much ARP fastener lube on the headbolts, and cracked the block there at the bottom of the headbolt hole. It ran fine in the shop and I thought I was ok until I found the exact foam in my radiator that you have there. I never put a mile on it and tore it down and scrapped the block when I found the issue. Sucks. You have a crack somewhere, or maybe a headgasket is letting combustion gas to push oil into the coolant…which I don’t see how that could happen…but crazy stuff happens every day.

 

"looks like if oil was mixing with coolant but its just a layer on top of the coolant and not mixing in with the coolant."
It's not going to "mix". The oil is lighter than water and will "float" on the water surface.
What Scott said.
" It ran fine in the shop and I thought I was ok until I found the exact foam in my radiator that you have there".

 

So your right. I have combustion gases in the coolant. I did an acid flush and I needed to get the coolant up to temp (hotter than I normally get it so I used a used stock temp thermostat which puts me at 195-203*F temp. I ran the engine at elevated rpms 1500 or so and had a no spill funnel on the radatior. I could see a ton of large bubbles coming our constantly. More "oil" in the coolant. After about 40min into the cleaning I stopped as it just kept going and originally I thought it was just burping out all the air. What is weird was after I stopped the big bubbling just kept coming out for at least 20min after I shut the engine off. It slowed down but it kept bubbling even after that long. I had enough waiting and I drained some coolant and put my new exhaust gas tester without even starting the car and it still bubbled enough to test positive. I don't think I cracked the block as I'm running speedmaster studs but I have no idea about the block if its cracked somewhere else. Why would it bubble for so long after? I know some of the cylinders would still hold pressure till it all leaks out but how much should it hold and how long till it bleeds out into the radiator. These are not tiny bubbles like I see online. I will post a video link below.

https://youtube.com/shorts/MvM-wmzqtgw?si=A07QHkrGOeUvVkcw

 

@00pooterSS ... I got an email with your response but I don't see it here in the thread. Weird....

Here was your response:
My steam vents are looped to the top of the water pump on the outlet side (basically right behind the top hose that goes to the radiator). This will force any air/steam into the upper hose which will push it to the top of the radiator and to the cap.

Now to go back about the looping. I don't believe that is correct but I think there are multiple ways to skin a cat. I believe the factory heater core loop is due to the dedicated expansion tank which the diagrams show no (heater core bypass inline with the circuit). This is required as you need the back chamber of the pump (engine circulation side) to loop hot water to the front chamber behind the Tstat seal to heat the pellets and activate the thermostat. I believe that all the truck water pumps have the tstats with the solid disk on tstat that seals the back chamber as they are expansion tank systems. Now alot of tstats (aftermarket) use holes in that back plate or raised sections to create a gap for fluid leakage from the back "hot" side and the cool front to activate the tstat pellets. So you are likely partly correct but it depends on what style Tstat your using and what mods have been done to the water pump. Now if you loop the heater ports your looping the cold and hot side which the red "hot side" (see post #4) goes right to the engine hot outlet and upper radiator hose. This bypasses the radiator flow a good bit and dumps cooler lower radiator fluid directly into the hot side to go right back to the top of the rad. This means a good bit of the cooler water from the lower rad is bypassing the engine inlet and cools the outlet basically looping the radiator. Now would this be needed on a Tstat that uses the backing plate that allows the hot coolant to "internally" bypass and activate the tstat? I've tested my Tstat and it opens around 172-175*F which is the temp the car will reach while traveling on the highway. I think either way your bypassing the rear and front sections of the water pump to activate the Tstat but you need to use the correct Tstat if you've plugged the heater ports on the waterpump. My Tstat has the raised backing plate for a gap, the same for the Gates stock LS3 camaro Tstat which is the correct Tstat for my LS3 camaro water pump.

https://www.yellowbullet.com/threads...ummies.621363/

also this - This guy talks about the Tstats with the holes on the back plate or raised sections go to about 8:45-9 min to hear
For the easy fix, I won't know till I have time to pull the motor apart. I'm planning to remove the turbo system, pull the heads and inspect. I have a .001" tolerance straight edge from amazon coming tmrw and some copper head gasket spray. I'll inspect/check for flatness and see what I find and then likely will spray the gaskets and slap them on. I did get a new full gasket kit which came with new stock style head bolts but this is a cheap @ss kit and I'm not sure if I will use the bolts over the speedmaster studs. The heads were milled to clean them up before engine assembly but the block was untouched. It's likely that my reused head gaskets didn't seal or like the added cylinder pressures from the turbo and pushed into the coolant passage. I'm glad nothing got in the oil or trans circuit.

 

Also I should add that I've already added an expansion tank. My rad cap is basically the same height as the steam port fittings on the heads, and then I have the steam port outlet on the driver side which angles up so its higher than the steam blocks on the heads which puts it even higher compared to the rad cap. So now my expansion tank is a few inches higher than the current rad cap, I've welded a -10an fitting into the lower rad hose which will go to the bottom of the expansion tank. The radiator cap gets a blank cap and the upper overflow 1/8npt will serve as my high point feed to the top of the expansion tank. This completes the circuit of bleeding air from the radiator to the expansion tank while the lower fitting feeds to the lower radiator hose (suction side). Then the expansion tank overflow nipple goes tot he factory location overflow tank. I've basically recreated the stock expansion tank system without the waterpump heater outlets or heater core. On the C3 vette the upper arm is less than 1/2" from the heater ports on the water pump so I have no choice but to plug them due to clearance issues. I'm confident that if I pull the heads and find nothing crazy that the new copper coated gaskets and expansion tank will solve this issue.

 

I posted and then later thought that you probably have your mind pretty set on how you’re going to do things and why you’re doing them the way you do. So I deleted my post. Looks like that was a fair assumption lol.

Hope you get it figured out man. Take care.

 

Well I started tearing into the motor last night. I decided to remove the exhaust/turbo system and pull the valve covers and rockers. I think used a compression tester and injected 100psi of compressed air into each cylinder. The idea was to see if I could get air out and into the cooling system which had a rubber glove zip tied over the rad cap opening. I did these for each cylinder for about 1 min each until they all leaked down to nothing. I ended up getting no movement on the rubber glove. I will yank the intake and heads next. I was kind of hoping to be able to see which cylinder was leaking so I had a direction to look.

 

I've been running one of Jay's blockoffs for a few years. It blocks off the bypass. I run no thermostat.

I can cruise the car around and it's run 5.6@127 in the 1/8th.

 

I know you weren’t necessarily talking to me but I just personally have been in the loop it camp because I have built multiple 1,000-1,500
hp late model corvettes/camaros that are true street cars with heater cores, aka looped heater hoses, and they can also sit in traffic for hours and or run 5’s in the 1/8

So I don’t know what any of it proves. Plugging, not plugging, looping, blocking off all seems to work.

But due to my personal experiences of being a tech and a builder with tons of LS and LT cars with heater cores (looped system) doing just fine making over 1k hp

And seeing tons of work trucks pulling way more weight than rated for and sitting in traffic here in Texas in August etc and never having issues, I say loop ‘em.

GM designed it to have a loop and all those examples didn’t have overheating issues. So I don’t see a reason to fix what isn’t broken.

However I have had some serious issues with overheating when people messed with the OEM flow layouts on some other makes and models so that also makes me want to stick to the OEM design if it isn’t hurting anything.

 

Totally, I ran a few combos with looped hoses.

But my turbo ls stuff always ran hot. My old Formula was always in the 220s.

The '67 will cruise around in the 190s in the summer. I'm kinda sold on the block off, before doing that and making the shroud better I was cruising in the upper 2teens.

 

On the ones that ran hot, did plugging them help over the looping, with no other changes?

And shrouds not being quite right go a real long way for sure. Been there man.

 

@Prostock John How is the warm up time? For me, I start the car and have the ECM take over closed loop by 140*F, that usually takes 10 min or so of idling just to get to that 140 mark, I don't like to drive off in open loop as I basically get into boost within 1/4 mile from my house (highway onramp). I would love to not have to worry about the Tstat sticking or failing and I'm not worried about having heat at all as its a summer/warm weather car and I have no heating system. as a side benefit air bleeding and no need to remove the stat to flush is a plus lol

 

I think I found the problem. I tore the motor apart on Friday/Sat and on the driver side head the top of the piston on #5 and possibly #7 were steam cleaned. The head gasket looked fine on the head side, the block side it looks like #5 the black coating was gone from the fire ring to the coolant passages above (1/4 moon shape). The #7 looked like it could have pushed to the right top as well but just in that one area and much smaller. Otherwise I found nothing else besides some milky oil in the threads/studs that goe inside the head and into the block. I cleaned and chased all threads and then installed new copper coated 3 layer cheapo MLS head gaskets. I torqued to 65ftlbs on the big studs and 25ftlbs on the small studs with Moly lube under the nuts. Last night I got everything back together and buttoned up. I haven't fired it up as I'm waiting on the block off plate from Jay's which hasn't shipped yet. Then I want to throw some coolant in this and start it up but I saw some rust in the cooling chambers around the cylinders so thinking I might need to do a rust cleaning/flush before putting coolant in it.


#5 after cleaning the block surface. Looks like a low spot at the top between the bolt holes (darker)

New copper coated gasket in

#5 up close on block side

Block side (flipped) so #5 is 2nd from left.

You can see #5 and alittle of #7 in this pic

 

Glad you found the problem. However, and this is just my opinion, though more than a few here may share the same .02, but cheaping out on head gaskets isn't a good place to cheap out. Time will tell if you've merely reinstalled the problem. What brand of head gasket failed? I've put together 3 different 427 LS motors, and none have ever failed. I used Cometic for the first one, as Darton sleeved 427, and GM LS7 gaskets on the other 2. Are you using bolts or studs? If bolts, I'm hoping you didn't try reusing the original bolts. Don't take offense-I've seen a few posts in some forums stating the OP did in fact reuse the non-reuseable bolts. While not common, it does happen here and there.

 

Something else I have noticed about my LS7 in a 2000 C5; if there's even a slight leak anywhere in my cooling system, the coolant temp actually increases, then drops way farther than usual!! IDK why, but it does. Cooling system stats:
A DeWitts radiator w/A4 connections, a 25% UD balancer, 160° stat, and an Edelbrock 8896 mechanical H2O pump. A few years back, I was ready to pull both heads, as it would lose enough coolant over the summer to go from the full mark to just below the lower level mark. No drips under the car. Freeway temps would go from 180° to 174°, then back again!! Always ran 178°-180° on freeway regardless of ambient. As I was looking at what to remove first to pull the heads, I saw a drip from a heater hose. It immediately evaporated. Then another drip in 15-20 seconds. The engine had heat sunk, increasing the pressure slightly until it dropped enough to stop. The cause? The factory sprung hose clamps had lost a tiny bit of tension. This happened several years ago, at least 4 years back. Installed a traditional hose clamp, and it has never leaked again. Saved me from buying $160 worth of head gaskets, and a Helluva lot of work!!! FWIW.....