Please help troubleshoot over pressurizing coolant 4jg2

[Mel31]

Last year we bought a 97 bighorn that wasn't very happy. It was overheating and bubbling like crazy in the radiator.

Since then we have completely rebuilt this engine. New chinese head, new cast liners and block resurface, new pistons and chrome tipped rings, new water pump, radiator, thermostat, diesel pump, starter motor, all internal bearings and who knows how many hoses!

It is still over pressurizing the coolant system. Fix one leak and it will spring another. The overflow bottle stays the same. If you take the cap off after its filled and running it will throw a jet up about 20cm high! When running with the cap off you can see the water rising and falling and then an air bubble will 'pop' up. Before the rebuild it had the steady stream of a head/gasket issue which is thankfully gone. We are still using water at the moment until we have the leaking prob sorted.

The radiator/water seems very hot even though the temp gauge says normal also.

Very thankful for any light that could be thrown on this issue!
Rob

[geeves]

who rebuilt the engine?
It does sound like it still has a leak. Before doing anything talk to your rebuilder.
My thoughts on the leak would be first the gasket is leaking second the block needs resurfacing third crack in the block. It could also be a dodgy head but those heads are well made and rarely have faults.
Running hot could be a bad thermostat it could be air in the system. It could be injector timing out It could be the viscous fan failing Air in the water jacket could be stopping the guage get a good reading.
Had to look at a pajero on the weekend Guage was normal but the steam cloud pointed us to a hose at the bottom rear of the head which had steam not water coming out meaning the water level was 1/3 what it should of been in the head. Hoses hard as metal so very dicey field repair. All we did was fill it up once cool enough Left the cap loose,then drove it back across the beach and home. Looks like he got away with it though. The great fear was that if we let the system pressurise it would blow the hose completely He put another 3 litres in on the way home.
Did the same with a LT1 powered cruiser though. Big mistake Those engines run a 98C thermostat so it boiled 200 meters further on.

[Mel31]

Rebuilt the engine myself. Had the block resurfaced when the liners went in at a reconditioner. I'm happy with how the gasket went in so hoping that would be a last resort. Are these things common for cracking blocks? I think I might go insane if it really is that!

It's not blowing any water into the overflow at all. Could all the leaks im having problems with be fallout from when it was pressurizing worse before the rebuild? It blew the bottom of the new radiator before I pulled the engine.

If it is air in the system how is the best way to get it out or make sure it's out?

Thanks
Rob

[geeves]

How long has the engine run since the rebuild? My prefered method is to just fill it then let it set 10 minutes or so then top up and run without the cap till just warm enough to circulate water. This must be done with the heater on full. Then keeping an eye on the level give it a few revs let it idle Repeat a few times so it has run at normal temp for 10 minutes or so turn off and fit the cap. 95 times out of 100 this is all thats needed Sometimes it will drain the overflow bottle when cooling so top up as req.
Some engines can be obnoxious in which case filling with the thermostat out can help
You say the guage is normal but the engine seems hot. Can you hold a hand on the top tank for 5 seconds? longer? If a plastic tank then running temp would only let your hand stay there 10 seconds before it hurts. Metal tank half that. A little water on the thermostat housing will give a more accurate idea of engine temp if it boils its above 100. If it takes 5 seconds to evaporate its around 80 which is what you want

[Mel31]

It has run for about 1000 km. has not been quite right whole time water leak wise. Motor wise it runs great! Compression seems really good.

The last time I fixed up all the leaks i sat it there at idle with the cap off and topped it up after each big air bubble until it had no more air bubbles which took about 30 mins, the water was sitting there still at this stage. Replaced the cap and drove it about a 10km round trip by the time I got back it had sprung more leaks and had lost about 500ml. The whole time through this the level in the overflow is exactly the same. This was done with the radiator cap off the Mu on it to see if it would make a difference. The one that was on it before has a 9 stamped on it. Could the radiator cap not seeming to let pressure/water out into the overflow have anything to do with it?

I really feel like it's not block/head/gasket related since before it did have that stream of bubbles which is now gone and it will eventually stop the rise/fall big blurpy air bubbles thing if you sit there long enough.

Running temp must be okay because it passed your tests from your above posts. Water took nearly 20secs to evaporate from the housing at idle.

[geeves]

thats sounding like the cap isnt releasing pressure. Is the tube to the overflow bottle blocked? Is there a leak in the overflow bottle? Where is it springing leaks? I know my wizard it terrible for getting the bottom hose on the radiator tight. New hose and it started leaking 2 month and 3000km after fitting. What are the ends of the hose connectors like. Any corrosion will prevent a good seal. Did you replace the spring clips with proper hose clamps. The springs are good new but not once they are x years old. They lose tension. A mechanic neibour told me they are ok if you fit then in the slots they had already pressed into the hose. I only use them where there is no choice.
Might be worth getting a new cap.

[Mel31]

Checked overflow tube for blockages for the tenth time just to be sure! It already has a brand new cap and the mu cap which works fine still makes no difference. If you take the overflow tube off at the radiator end and blow it bubbles away and spurts water out of the reservoir. Surely the radiator pressurising it would be doing the same when the system got to the required psi to make the cap lift and let the pressure through into the overflow. This got me thinking is the new radiator identical in the way the tube/hole is set up to go to the overflow. Sure enough it isn't! The old blocked radiator that came out of it has a hole twice the size and about 2mm lower than the hole in the new one. Maybe that's just high enough that even when the base of the cap lifts it's not opening the hole? Will have to be tomorrow's mission to try drill it out a bit lower and see if that helps. Wish me luck

[geeves]

2mm would add 20 or 30psi to the opening pressure. Certainly a trap for young players. Now the best answer is to find a cap that fits that radiator