Please help, I've looked through many posts but I can't find an answer to my cooling issue. I bought the truck with a ls1/243 heads, mid lift cam and little did I know warped heads from overheating! I thought it was due to a bad rad cap and a malfunctioning temp gauge. So I pulled the heads, decked them, new rad cap, sweet aluminum cooling hoses and called it a day. I pressure tested the system and its been running at about 230 all winter. I opened it up on the freeway today to kill a F150 and got home and I heard the boiling in the radiator as soon as I got out! Back to the same problem. I figured it was running a little hot because of the old radiator that was probably made for the 350 that was originally in it. I can hear a distinct hissing from the area under the throttle body but can't pin point it. I sprayed wd40 all around the area hoping to hear bubbles and locate the leak. Could it possibly be a water pump bearing that when under heat and pressure gets leaky? There are no visible leaks which is making this difficult. Should I replace the water pump before I do anything else? Also, my starter got heat sink and the truck has to cool down before the starter will work again. Will a high end starter fix that problem? Thanks again, ya'll always step up when I have questions.

 

What temp thermostat are you running? Fan? Does it have a shroud?

 

Is the problem that your temp gauge says you are overheating or do you just hear the sounds?


What coolant mix at you using?

 

It's a 180 therm, dex 50/50, fan shroud yes for dual electric fan both come one at same time. It's a new auto meter water gauge and its hooked up to the head on back passenger side. I live in Phoenix and it's starting to get warm. It was starting to move up to 250 in my driveway then I shut it down. the boiling sounds were very audible and the hissing leak was pretty noticeable too. Now I'm assuming it's loosing pressure and that's why its boiling. I'm not that good with cooling systems tho

 

I know it sounds stupid but have you checked to make sure the fans are mounted/wired correctly, I fixed a car last year that had fans mounted on the inside of the radiator(engine side) trying to push air to the front. Worked much better after I wired them to pull air in.
To answer your question on the water pump. They usually fail and leak when hot or cold, Although they will leak faster if pressure builds up. 250* is pretty hot and likely going to boil no matter what, You also have to remember that when you shut it off the water is no longer circulating so it can get localized hot spots (heads are still trying to dissipate heat) so it will continue to rise for a few minutes. (That's why you should leave it running and cool it down of possible.)
Another possible cause is the tune. If it's running to lean or the timing is off it can cause overheating.

 

Good info. Yeah, fans are mounted to inside but pulling from front to back. They are pretty powerful and move a ton of air, I don't think they are it. Well, *****. If I go with a new aluminum rad with nice 1inch cooling tubes do you think that's a sure fix? I would be much happier if I could get operating temps to 200. The old rad is old as f. I really wanted to install AC but if I'm having this much trouble who knows if that will happen. as for a tune my machine shop said don't bother. It runs awesome and they said don't waste my money unless I do a serious mod.

 

What mods were done besides cam? Headers? Remove cats? MAF relocated? Bump in compression?

A better radiator can't hurt considering your location.

 

Just cam and 1:7 YT roller rockers. Wilson fast. MAF got moved from throttle body to behind air filter about 3 foot away. She breathes real easy. No cats, truck exhaust manifold straight out to 3" exhaust. Looks like my long tube cash is gonna get eaten up by my new radiator. I've lived in the desert my whole life and had cooling issues on every ride I've ever had, time to put a stop to it.

I was searching for rads, Rnd fabrication looks pretty good. Any recommendations? The eBay radiators scare me, they are cheap but I don't want a cheap *** made radiator.

 

I'm actually surprised that it runs well on the stock tune with all those mods either that or someone else tuned it before you got it. It wouldn't hurt to see what the afr is.
There are actually quite a few cheap radiators on ebay that are built pretty well.
I know a few people that have used them and a bunch of people 0n another forum have used them when putting an LS1 in S10's.

 

Absolutely.....a water pump can leak under increased pressure and temps.....but never leak a drop at normal temps. I recently changed my water pump and had a hell of a time finding the leak.....it was the pump bearing. It would spray coolant out at speed and rpm and when the temps were UP. But pop the hood, rev it, let it get hotter with the a/c on....pressure tested it.....NOT A DROP would come out. Sneaky little bastard......

For the starter issue....simply get a thin piece of sheet metal and mount it inbetween the starter and header pipes. Make sure you don't lay the sheet metal against the starter though.....leave a littler space for air flow......but so it won't get direct radiant heat from the header pipes.

Also....could have a warped deck on the block.....possibly.

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Jayred,

Also, since its an LSx implant into a truck......the factory radiator and factory shroud attached to the radiator are a very important part of the cooling efficiency.

Is it a custom cooling set up.....or do you have the factory radiator/fan shroud in the truck...? Without that shroud, it can cause endless cooling problems......

I see some custom set ups work.....even some without the shroud....but its really important to have air sucked through the shroud and blasted across the entire surface of the radiator.....without the shroud properly attached the air flow gets lost.

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This time of year, when we see these comments, the culprit is usually airflow as others above have pointed out. ^ If the temperature is spiking when you aren't moving, then I'd also be suspicious of how the fans are flowing air over what you have.

(If you maintain the proper temperature while moving, the radiator you have now should be fine - that may not be the case as it gets hotter.)

 

I ran into something like this and I found one of the water pump gaskets was leaking. Wasn't obvious either but the car ran hot and would boil when you shut it off hot. Replaced the water pump gaskets and all the freakiness went bye bye.......

 

I suspect I have a air flow and radiator issues. Normal temp during speed is about 225 so that tells me a new radiator might be the fix. I'm going to try a new aluminum from RnD with my shroud and fans and if it is better but not optimal I'll invest in the new shroud and fans. I did just change the water pump gaskets when I pulled the heads. God help me if the block deck is warped. And a shield for my starter to boot. Thanks again for all the help. I'll post again after I find what worked.