Oil in coolant, JCB 3C

CHRISEEBOY · Post #1 by **CHRISEEBOY** » Mon Jun 07, 2021 3:29 pm

I have got my 3C up and running and started to put it to work. I ran it for about half an hour and then stopped and did a routine check up. I noticed one of the legs was leaking oil, but not too fussed about that. Oil level was fine. Checked the radiator and found spots of oil in the coolant. At first I thought the rad may have been dirty and the new coolant had picked up some filth clinging to the inside.

Ran it for a couple of hours the next day and now my coolant looks like milky tea and the oil level has slightly dropped.

This engine had siezed (bearing shell to crank shaft, cylinder 1) and has undergone a fairly comprehensive rebuild. I have replaced the headgasket so im confident that its not the culprit.

Just not sure where to go from here. How would I go about diagnosing the cause of the leak?

Post #2 by **Jeremy Rowland** » Mon Jun 07, 2021 7:31 pm

Chris I would be looking at the engines oil cooler (I assume it has one fitted?)

Jeremy

MrF · Post #3 by **MrF** » Mon Jun 07, 2021 7:50 pm

The engine doesnt have a oil cooler on the 3c3, the cooler in front of the rad is for the transmission if you have a auto box. The only places the water and pressurised oil are both in is the head and the cylinder block. So it has to be the head, or the block or the head gasket at fault.
Have you retorqued the head down now after its had some runtime? The manual states half a hour, then retorque, then repeat again after 50 hours runtime.

CHRISEEBOY · Post #4 by **CHRISEEBOY** » Mon Jun 07, 2021 9:18 pm

Ahh, didn't know that MrF. I have not retorqued the head nuts. I took them down to 136Nm as per the manual but didn't realise they would need more after half hour runtime. Do you think it would be prudent to take them down to say 140Nm just incase the bolts have been stretched over the years?

Post #5 by **Jeremy Rowland** » Mon Jun 07, 2021 10:15 pm

MrF wrote:The engine doesnt have a oil cooler on the 3c3, the cooler in front of the rad is for the transmission if you have a auto box. The only places the water and pressurised oil are both in is the head and the cylinder block. So it has to be the head, or the block or the head gasket at fault.
Have you retorqued the head down now after its had some runtime? The manual states half a hour, then retorque, then repeat again after 50 hours runtime.

Thanks Phil :thumbup:

I am not up on these engines so what you say makes sense as they are the only other places where the two pressurized systems are together.

Jeremy

MrF · Post #6 by **MrF** » Tue Jun 08, 2021 2:25 pm

I think the hot ticket is to retorque them as per the manual instructions as after they've had a few heat cycles in they do bed down.
There has been a few post gasket changes on here where they started to weep, then when retorqued they had slacked off a lot but after redo'ing all was well.

Apart from that I'm probably not the best person to comment on if bumping the torque up is a good idea as I have one motor I have never been able get to seal up 100% reliably (and yes I tried that at one point, and it didnt help) and I'm avoiding anything which might result in having to lift the head on the other one. 4Nm is neither here nor there though and at 3% within allowed error of the torque wrench calibration itself.

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