Randall Posted November 7, 2011 Share Posted November 7, 2011 Hi, I recently rebuilt a 2.8 from a junkyard had a machine shop deglaze walls polish crank and check clearances. I put standard size rings and bearings back in and installed a rebuilt head. I put a new thermostat in and a radiator that I pulled from a junkyard that appeared to be in awesome condition. I installed the freeze plugs by hammering them in with a socket not using any sealant. Ok so now to the problem First drive it started to overheat top hose was cold bottom hose very hot. I checked the thermostat and it was opening up. Also I let it sit after that first drive and I came back out to find that the 2 nd to last plug on passenger side had popped out. Put a new one in and drove the car a couple of days without a thermostat just fine. Put the thermostat back in and tried another trip this time while driving the 2nd plug from the front popped out. So I pulled over and could have sworn I blew up my motor. What could be causing this? How will I know if I have damaged anything? Quote Link to comment Share on other sites More sharing options...
Graphitez Posted November 7, 2011 Share Posted November 7, 2011 (edited) I am not an expert, but i use RTV sealant on all the freeze plugs i have installed. Is the car blowing white smoke out the exhaust? Head gasket could be leaking between the coolant ports and cylinders,causing compression to enter the coolant chambers in the block,thus popping freeze plugs out like tic-tacs. Edited November 7, 2011 by Graphitez Quote Link to comment Share on other sites More sharing options...
Randall Posted November 7, 2011 Author Share Posted November 7, 2011 I just completely rebuilt the motor and there is no smoke or leaks starts up great and runs strong. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 7, 2011 Share Posted November 7, 2011 Ok so now to the problem First drive it started to overheat top hose was cold bottom hose very hot. I checked the thermostat and it was opening up If the thermostat was open, the top hose should be hot. You removed the thermostat and then it did not overheat. Sounds like you have the thermostat installed backward. Quote Link to comment Share on other sites More sharing options...
Randall Posted November 8, 2011 Author Share Posted November 8, 2011 I installed it the way the fsm had it pictured and the same way it was on my old motor so I doubt I installed it wrong. Btw I installed it spring down. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 8, 2011 Share Posted November 8, 2011 It sounds like you did have it properly installed. You said you checked the thermostat and that it was opening. How did you do that? Quote Link to comment Share on other sites More sharing options...
Randall Posted November 8, 2011 Author Share Posted November 8, 2011 Heated it up on the stove to make sure it would open this was on the autozone thermostat. I then tried the one that was in the old motor before I pulled it (this one worked before I pulled the motor) and that didn't help either Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 8, 2011 Share Posted November 8, 2011 Let me summarize: - Engine was rebuilt. - Driving with either the original or new non-OEM thermostat causes it to overheat and blow out freeze plugs. - Removing the thermostat solves the overheating issue. - You have verified that both thermostats open in hot water. - You have verified that the thermostats are properly installed. - When engine overheats, top rad hose is cold, bottom is hot. The symptoms don't add up to me - cold top hose suggests lack of coolant flow. That's usually due to the thermostat being installed upside down or having failed closed. I suppose it's conceivable that you have an air pocket that is blocking coolant flow with the thermostat in, but that purges itself without the thermostat? Doesn't sound likely to me and I've never done anything special to purge coolant on an L6. Did you look at the water pump during the rebuild? Any damage to the impellers that would reduce flow? Anyone else care to take a stab? Like I said above, the symptoms don't add up to me. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted November 8, 2011 Share Posted November 8, 2011 Initial overheating might have been air in cooling system......very common on first starts. I always run the engine a few times and ease up to the point that the thermostat should be near to opening. Then I shut it off and let conduction do it's thing. Upon restart, I am usually greeted with a significant lowering of coolant level to which I add coolant and let run until I see flow through the radiator. Quote Link to comment Share on other sites More sharing options...
z-ya Posted November 8, 2011 Share Posted November 8, 2011 How far are the core plugs in the block? The edge of the plug should be flush with the machined surface of the hole. Sealant won't hold it in any better,it will just seal any minor leaks. What pressure radiator cap are you running? Does the thermostat have a bypass hole in it? Quote Link to comment Share on other sites More sharing options...
Noddle Posted November 8, 2011 Share Posted November 8, 2011 Initial overheating might have been air in cooling system......very common on first starts. I always run the engine a few times and ease up to the point that the thermostat should be near to opening. Then I shut it off and let conduction do it's thing. Upon restart, I am usually greeted with a significant lowering of coolant level to which I add coolant and let run until I see flow through the radiator. I all way drill / punch a small hole in the base of mine ( thermostat ). Quote Link to comment Share on other sites More sharing options...
Randall Posted November 9, 2011 Author Share Posted November 9, 2011 I'm taking the radiator to be inspected and ordering an oem thermostat. I am going to pull freeze plugs and reinstall with sealant on passenger side of block. I am running a 13 lb cap. I will let u know when I get it started up again. I am going to put new oil and filter in also since I have driven it a 100 miles already. If something was damaged from the multiple overheats what would I be looking for? Would a compression test tell me what health the motor is in? Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 9, 2011 Share Posted November 9, 2011 (edited) I didn't see any sure signs of over-heating in your description. Signs of improperly installed core plugs maybe. You have a 13 psi radiator cap, did it let go? Or did the core plugs just pop out when the engine started to get warm? Looks like you have a 13 psi cap and 5 psi core plugs. Edited November 9, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
Randall Posted November 9, 2011 Author Share Posted November 9, 2011 I hammered them in using a large socket till flush with block how else to do it? Quote Link to comment Share on other sites More sharing options...
ozconnection Posted November 9, 2011 Share Posted November 9, 2011 I'm with Zmanco, strange symptoms indeed. The installed thermostat will act as a kind of restrictor in the block cooling system. It will allow block coolant pressure to build up to around 25-30 psi. When you remove the thermostat out of the system, coolant pressure will only be as much as the radiator cap will allow and is 13 psi in your case. That's your reason for your core plugs popping out when the thermostat is in. The core plugs can be either made from a brass type material or steel. Which ones do you have in your engine? I think you have to be careful with the softer brass ones when installing them. What I can see happening is that whilst you're driving them into place with a socket that is smaller than the lip of the plug, the central part of the core plug 'depresses' so that the lip diameter alters very slightly. The fit is therefore not as tight in the block. When I built my L28 recently, I used a piece of wood over the lip of the core plug to get it started and then drove it home 1mm below the machined hole in the block with a socket that matched the lip diameter of the core plug. The shape of the core plug was not changed by hammering, it only varies because of the fit into the block. On my L28, I have an external bypass line from the base of the thermostat housing to the intake side of the water return hose from the radiator. I know some engines don't have this external bypass line. Im my case I close up the bypass hole in the thermostat as it's not needed. Just some thoughts on the subject and I think your engine will be Ok. Good luck mate. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 10, 2011 Share Posted November 10, 2011 (edited) What did the temperature gauge show before the plugs popped and how long did the engine run after? One will give an indication of if there was overheating and the other will give some detail on probability of damage. Edited November 10, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
Randall Posted November 11, 2011 Author Share Posted November 11, 2011 I've never seen the gauge go over 3/4 but the last time I noticed it I was on the highway so I don't know how long the freeze plug was out Quote Link to comment Share on other sites More sharing options...
Randall Posted November 11, 2011 Author Share Posted November 11, 2011 Should I worry about bottom end damage Quote Link to comment Share on other sites More sharing options...
rejracer Posted November 14, 2011 Share Posted November 14, 2011 (edited) Don't worry about bottom end damage, test for it! A compression test will be a very good indicator of the health of the engine. If you lose coolant very quickly, it can overheat the engine and not register on the needle as there is no coolant flowing to transfer the engine temp to the sending unit. Get those core plugs back in the engine, properly installed, and do a compression test when it's at full temp. Of course test for coolant flow first by pulling the upper hose and start it up to check to see it pumps fluid out when started. I made an adapter to go from our radiator hoses to 5/8 coolant hose and catch the fluid in a drip pan. Actually I made 2 of them when I was flushing an engine I bought for heavy rust scale. With this setup, it was possible to run the engine with 2 hoses in a bucket, making testing the flow of the coolant very easy. The only other thing I can think to do is to put the plugs back in and pressurize the system to 20 or so PSI. If they pop out, you have plug problems. Also test the flow of the radiator. How they look has little to do with how they flow. Do the flow tests without the thermostat installed. Hope that helps you troubleshoot. Edited November 14, 2011 by rejracer Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted November 14, 2011 Share Posted November 14, 2011 Hammering in the freeze plugs with too small a socket can cause them to bow in the center which can cause them to not fit as tightly. Quote Link to comment Share on other sites More sharing options...
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