After about a years work I finaly got her running a few weeks ago (complete engine overhaul due to overheating). She ran fine on the short stretch. Two weeks ago we drove about40 miles (nice and easy) Close to home the temp needleis movingtowards hot, and when I stop, theirs like steem coming out of the radiatoroverflow. After a cooldown I refill the radiator with 2 liters of water (about half a gallon ?), and start up again, al good, a spin for 5 miles and when I come home, water is running out the overflow.
So I am thinking cilinderheadgasket, next morning, refill radiator and I start the engine with the radiator cap off (to check for bubbles or to much pressure in the radiator). Nothing happens until (I think) the thermostat opens, at that moment water shoot out the radiator top like Old Faitfull (when he was younger).
So I concluded that the cilinderheadgasket was blown, or I have a crack in the engine or heads somewhere .
I took the engine out, and removed the heads. The gasket looks fine (didn't drive more then 150 miles with it).
Question : Was my test correct, and with it my conclusion ?
And what else could it be ? and how to check for it?
Is there an easy way to test the waterpump ?

Thx

 

If your car is a V-8, it is possible for the head gaskets to be installed backwards. If you are sure that the gaskets are placed with the printed "FRONT" towards the front this can be eliminated. This can be an easy mistake to make ona SBF, I almost did it myself even though I knew better.

If this is right, then it might be adviable to change the water pump. You should really do this when you rebuild an engine anyway. Also be sure that the pump rotation is right, there are "reverse flow" pumps available that will not work right with a V belt setup, or vica-versa. (I think that some aftermarket serpintine kits use a standard rotation pump)

Make sure your radiator is clean, and it has at least 3 rows of tubes if you have a V-8.

Change the thermostat even if you already have a new one, it might be defective, and also it is not really good for them once they get really hot. Make sure your thermostat is not more than a 185 degree unit.

 

+1 JMD

It sounds like you had a massive air lock...hence the old faithful thing.
You must make sure both radiator and heater core are not blocked.
It sounds like you used the old water pump on the rebuild? Not a good idea IMO, but it must havebeen working to build that much pressure.

If you install a new or recored radiator and heater core, make sure you use a filter in the top radiator hose to collect all the crud that comes through the system before it blocks the rad again.

 

Are you sure the water pump is pushing water the correct way? I was sold a reverse water pump for my '84 Jeep CJ7 once.. It did the same thing...

 

The gaskets were installed correctly, but I 'll double check when installing the new ones. (it is a V8)
The waterpump has a C8something code (so I suppose a 68'er), do they come in reverse rotation ?
How do I test if she's working right (engine is on a enginestand)?
So Old faithfull was an airlock, and not a blown gasket (as I noticed when removing them)?
How do I avoid another airlock, or what to do when this happens?

 

You need to burp the system. Get an overflow tank on there. After heating and cooling the water mix a few times, the air will get out through the overflow tank.

 

you could try pressure testing the system with a tool thats pretty much a pump and a gauge it will work a air bubble out if theres one

 

An air lock can ocour when a bubble of air is trapped behind the thermostat. The air will effectivly insulate the thermostat from the coolant so that the thermostat will not open untill the engine is very hot.

A fix for this can be to drill a 1/8th inch hole in the edge of the thermostat to allow the air to pass around the "valve". If this is not somthing you want to do, you can loosen the bolts to the thermostat housing and "crack the housing open a little (until coolant comes out) once the cooling system is full.

When you rebuilt your engine, did you have the heads and block magnafluxed? I ask because you had an overheat issue prior to the rebuild, the heads or blockmight have a crack in the combustion chamber. I worry about any engine that violently pukes coolant, (especially when it pukes more than once, like over and over again) in my experience this has always indicated a compression leak into the coolant which is never good news. Ifor certaincan not say that this is your problem, but I would check things out very carefully before putting the engine back in.

 

You can pressure test the engine out of the car as well. You can get "rubber stoppers" that plug the coolant inlets and outlets, and test with one of these units using compressed air only. if the pressure leaks down, and you can not find an external source of leakage, this would indicate internal leakage (duh I guess )