Christian S. Hansen
Post Number: 946
|Posted on Monday, 15 October, 2018 - 18:41: |
1936 HJ Mulliner 20/25 GBK44
Current project involves chasing down a possible head gasket leak. Seem to have combustion gasses in radiator and coolant in oil sump. I am preparing to pull the head but it seems that a more specific diagnosis of what I might be looking for is in order.
In an earlier post on a different chassis something called a leak down test was suggested. Am I correct to assume that this involves pressurizing each cylinder one at a time and comparing the time it takes for the pressure to dissipate or "leak down"? I further assume that while a compression test checks the compression generated at the top of the piston stroke, a leak down test should best be performed when the cylinder is stationary at the bottom of the stroke? I am hoping to isolate the location of the leak between combustion and coolant. Optimistically I hope for head gasket. Maybe a leaking copper coolant tube in the block? Perish the thought of a crack somewhere in head or block. Anyway, will this tool assist in this regard?
Posted From: 22.214.171.124
|Posted on Tuesday, 16 October, 2018 - 19:46: |
Very often due to stretched and corroded studs, and many times where the nuts are right down onto the threads having no effect.
There are 38 copper tubes in the block and as many in the head and are in fact ducts for the studs due to iron founding difficulties.
(Message approved by david_gore)
Christian S. Hansen
Post Number: 948
|Posted on Tuesday, 16 October, 2018 - 21:07: |
After I mentioned the copper tubes, I then thought why in such a case could combustion gasses get into the coolant. Would have to be a blown gasket between cylinder and the tube. Perhaps a combination of a head gasket blown in the area of a defective tube, and thus actually two problems simultaneously? It would fit the symptoms of coolant in the oil without getting into the cylinder. Observation of the spark plugs showed no signs of moisture or rust which I would have expected if water was getting directly into a cylinder thru a blown gasket. Coolant was however in the oil when I drained it. Car has been sitting for some time while fussing with other projects so I suspect that water found its way into the sump even with engine idle as it would in the case of defective tube. In due time I will do the pressure test to try to determine which cylinder is leaking but at the moment have some other stresses prioritizing my spare time.
I should add that the engine fires immediately, idles smoothly, and runs fine in spite of the problem so at least the car can move around under its own power on and off the trailer during the move to Montana. As a precaution I keep the radiator empty and only fill briefly when needed to run the engine.
Post Number: 1965
|Posted on Wednesday, 17 October, 2018 - 05:25: |
Christian, this is the type of cylinder leakage tester you need to carry out and confirm all types of cylinder, head gasket, valve issues and more.
Pressure test is I thought was a compression test!
Whistle is a must, any help just ask.
Christian S. Hansen
Post Number: 953
|Posted on Monday, 22 October, 2018 - 17:27: |
For no particular reason I had always considered the lighting and ignition switch to be bullet proof and until now they have always worked flawlessly on all my various RR and B vehicles. In the case of this 20/25 however during the period of recent storage the light (left) portion of the switch has become jammed and will only go from "off" to the parking light position but no further into the headlight position. Ignition side which is either "off" or "on" works fine. I'm not really looking forward to pulling things apart and will put that off until later anyway as the current goal is simply to get it relocated to my facility in Montana. In its current state it does however prevent driving at night which is a nuisance. Anyone have any thoughts as to what could have happened?