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2007 LQ4 6.0 Engine swapped into a G-body
I've had issues with this engine since i swapped it into the car. It was a junk yard motor and everything looked good when I bought it.
After install I noticed the engine used coolant a little, and then after a longer drive (from in town to highway, to an in town stop light) if the coolant system was filled completely it would pop the lower radiator hose off the car.
The radiator was cleaned and some repairs made prior to the install at a radiator shop. It's a larger 4 row brass radiator. I've used hose clamps with worm gears as well as the t-bolt style, both don't hold.
I bought a "block tester kit" and the results said it may have a partial leak as the fluid turned green rather than totally yellow.
I did a leak down test on the engine and found I had around a 3% drop across the entire engine with no radically different numbers on any cylinder. So that's good.
I decided to pull the heads tonight. The coolant would still blow off the lower radiator hose if I completely filled and bleed the system with a spill proof funnel..
I found that the MLS gaskets have no breaks in them. .and all the piston tops look the same and have carbon build up on them. I can even see some factory cross hatching.
I'm so confused now. I'd just like the car to run right and not put coolant all over the road after I sit at a traffic light. Was it the gaskets or something else? 317 heads.. look normal? drives side bank passenger side bank head gasket 1 head gasket 2
Rotate the crank and closely inspect each cylinder while the piston is at the bottom of the stroke. A leak down test should be done with the piston at TDC and could mask a failed cylinder wall if it’s below the piston. Did you happen to do a compression test before taking it apart?
I put a new radiator cap on it, and it has a new thermostat in it as well. I'll check the head, good tip. A friend of mine said it could be lifting a bit? No boost was used on this motor while I've had it, but maybe? When I pulled the heads, only one head bolt was discolored black, the rest looked aluminum in color.
I'm starting to wonder if maybe I had an air pocket this whole time and couldn't get it out? When I'd try to bleed the cooling system though it'd boil out of the spill proof funnel even after the engine was off. If you reved it up, you'd watch bubbles rapidly come up the neck of the funnel. If I messed up and pulled the heads, that's fine. I'll be out a bit for the head to get trued, some head bolts and time.. but i'd really like to find out why my cooling system was getting overly pressurized. The system would loose pressure after the motor cooled down as well. It'd go from a firm upper hose with no play if you squeezed it, to a hose that felt like there was no coolant in it when it cooled off. For every 40 miles or so, the engine would also use a little bit over a pint of water.
I've used block test fluid for 20 years, if it changes away from blue in any way there's hydrocarbons present. It doesn't have to fully change to yellow.
Cylinders number 3 and 4 have a little bit of a clean spot on the outer edge, and one of the intake valves in a little cleaner than all the others on a cylinder that could have been number 3 or 4.
You really should take the heads to the machine shop to have them checked and decked. May be warped or cracked.
Funny story, in 94 I bought an acura with a cracked radiator and put a new one in it and a new cap. It kept blowing the radiator apart or popping hoses. I did a new headgasket and checked everything and kept doing it. A few weeks later I found my old cap out in the parking lot (no idea how it got there) put it on and never had a problem again. A new part isn't always a guarantee. I'm a tech and I've seen many brand new parts be bad, shouldn't happen, but it happens.
Last edited by 00pooterSS; 09-19-2018 at 11:59 AM.
I've seen. a crack in the cylinder wall do this as well, pressurize the heck out of the cooling system but in my case it blew the lower tank off the radiator... (Old 350 V8)
Heads will be going to the shop tomorrow. Maybe they'll find something.. of maybe they are just warped.I'll let you know. But since you're here.. which head gasket should I be using for an N/A Lq4 motor? LS9? Going to put a cam in it.. figured why not, it's easy right now..
It's best to go with the gasket that's sized for the bore, some boosted guys like to go with the LS9 gasket and say that it holds better at high boost, whether that's true or not I don't know.
The LS9 is for a 4.065 bore and you have a 4", you could do LS9 but the right gasket for you would be a gasket for a 4" bore. So a stock gasket would be perfect.
Now is the time to go to thinner gaskets though if you want to bump the compression a tad, but they're expensive and don't make that much of a difference. I'd personally just go with a stock MLS gasket for 4" bore.
The LS9 gasket will have a small negative effect on compression and quench
I put a new radiator cap on it, and it has a new thermostat in it as well. I'll check the head, good tip. A friend of mine said it could be lifting a bit? No boost was used on this motor while I've had it, but maybe? When I pulled the heads, only one head bolt was discolored black, the rest looked aluminum in color.
I'm starting to wonder if maybe I had an air pocket this whole time and couldn't get it out? When I'd try to bleed the cooling system though it'd boil out of the spill proof funnel even after the engine was off. If you reved it up, you'd watch bubbles rapidly come up the neck of the funnel. If I messed up and pulled the heads, that's fine. I'll be out a bit for the head to get trued, some head bolts and time.. but i'd really like to find out why my cooling system was getting overly pressurized. The system would loose pressure after the motor cooled down as well. It'd go from a firm upper hose with no play if you squeezed it, to a hose that felt like there was no coolant in it when it cooled off. For every 40 miles or so, the engine would also use a little bit over a pint of water.
My project finally got to the point of filling the radiator up and I just left the hose to the steam ports off while I filled the
radiator and eventually water came out of the steam port line, then I put the hose on clamped it down, finished filling
radiator, no air pockets.
... When I'd try to bleed the cooling system though it'd boil out of the spill proof funnel even after the engine was off. If you reved it up, you'd watch bubbles rapidly come up the neck of the funnel. If I messed up and pulled the heads, that's fine...
Could have just needed to bleed a lot of air from the cooling system, but to me this sounds more like combustion gasses getting into a water jacket. Heads/head gaskets would be the best case scenario here. If the heads check out ok, I would get a real good inspection on the block. Based on your good leak down test I get the feeling there’s an issue below a combustion chamber.
Over pressurized cooling system is from combustion gasses getting in from a bad seal with the head gasket. It’s not something that is gonna show up in a compression test or a leak down test. Basically it’s just one of those things that you know it’s happening because you get a few signs like - hoses blowing off, or rock hard hoses, or collapsed hoses after it’s cooled off - you basically just know.
Thanks for the replies. I thought it was head gaskets too, but when it returned good numbers on the leak down test I thought, would this show a drop somewhere due to the leak? And to me, the head gaskets looked fine. Didn't get the heads to the shop today,decided to wait for the cam springs to show up and have them cleaned, inspected, and trued if needed. Then I'll do valve seals and springs.
00pooterSS, good info about the LS9 gaskets, I appreciate it. I'll just go stock then (and save some money as well).
I really don't want to break down the entire block for this.. I was trying to get the car back on the road rather quickly.. but I'm guessing that could be the only way besides trying the new head gaskets and if it doesn't work, pulling the entire motor?
I will say that the engine oil looked fine and didn't have the normal milkshake you'd expect. Coolant really looked fine as well... when I kept it inside the motor. Once when I was getting aggressive about burping the system, I relieved pressure on the cap with a welding glove on. Some steam came out, and then brown coolant and then green. Maybe that helps. I normally don't do stuff like that, but I was running out of ideas besides pulling it apart.
You're assuming the leak is like a faucet running, but that's not how this works. Maybe back in the days of composite gaskets where a failure was catastrophic - allowing coolant to pour right into the cylinder or into the crankcase - but with today's multi-layer-steel gaskets, they only let a little bit of gases by when cylinder pressures are highest. The rest of the time, they pretty much stay sealed up. Unless you're running massive amounts of boost or nitrous or something that is going to make serious cylinder pressures, you're not going to blow a MLS gasket like those old composite gaskets. All you're gonna get are these little signs that something is not right like constantly having to bleed your system, or having to top it up all the time, or the other things that have been mentioned. The days of billowing white clouds of exhaust or milkshake oil are pretty much things of the past.
You're assuming the leak is like a faucet running, but that's not how this works. Maybe back in the days of composite gaskets where a failure was catastrophic - allowing coolant to pour right into the cylinder or into the crankcase - but with today's multi-layer-steel gaskets, they only let a little bit of gases by when cylinder pressures are highest. The rest of the time, they pretty much stay sealed up. Unless you're running massive amounts of boost or nitrous or something that is going to make serious cylinder pressures, you're not going to blow a MLS gasket like those old composite gaskets. All you're gonna get are these little signs that something is not right like constantly having to bleed your system, or having to top it up all the time, or the other things that have been mentioned. The days of billowing white clouds of exhaust or milkshake oil are pretty much things of the past.
Thanks for the insight 8Lug. I'll admit, I've been trying to get smart about MLS gaskets since I've been trying to diagnose this problem, but haven't found too much info about failure. I guess I'll get the heads machined this week if needed, clean the block surface, put it together and see what happens.
09-17-2018, 10:48 PM
LQ4 blowing lower radiator hose off the radiator 
