New pressure and temperature sending units for a 450 straight.

[Cle Elum John]

Hey
I am looking to upgrade a 450 straight diesel to electric pressure and temperature gages. I need some help with the threads on the sending units. The manual and parts list are not much help.

The measurements on the coolant sender looks like a 1/2" NPT (about .84" od treads). Question: Is it straight thread or NPT. I suspect it is NPT but that is only guess. Can anyone verify the diameter and thread type.

The pressure sender looks like a standard 1/8" npt tread. Can anyone verify that? It's hiding in a corner behind a fuel filter. It is hard to measure and it will be a bear to get to.

The repair manual says at 2500 rpm oil pressures should be between 45-65psi. Does anyone have a feeling what the reasonable low pressure cutoff would be. I am thinking about adding a low pressure idiot light. I really need all the help I can get. I have had cars that where normal pressure was 7-8psi at hot idle. I have no clue for a this machine. I suspect something less than 10psi would be ok.

I would like to have the correct parts on hand before starting. Any help will be appreciated.

Thanks
John

[Jim B]

I'm a bit confused here. You say you want to convert to electric pressure and temperature gauges. You say coolant sender, to me a sender would be for an electric gauge, a mechanical gauge has a capillary tube with a probe at the end mounted through an adapter fitting in the head. For the oil pressure you say the sender is hiding in a corner behind a fuel filter. Here again, a sender would be for an electric gauge, a mechanical gauge would have a small tube or hose supplying oil at pressure to the gauge. The parts catalog shows a 450 has electric gauges.

The oil pressure tube (or electric sender) will connect in to 1/8" NPT port in the flywheel housing plate, the tube connects to. The mechanical temperature gauge kit has a male 1/2" NPT adapter which threads into the head and has the special female thread for the capillary tube clamp nut. If it is an electric sender, it might have 1/2" NPT thread or it may use a reducing bushing arrangement, from the 1/2" NPT port, for the sender. NPT means National Pipe Thread which is tapered.

In any case if you are installing electric gauges, I suggest you get the gauge and sender together, in a kit. Electric gauges and senders must match to work correctly.

The JD 2030 (4.219 diesel) wheel tractor used an indicator light for engine oil pressure, part # AR27977 (sub for AT85174). A standard automotive indicator light switch pressure range should be ok for your engine. Lavoy or a parts store should be able to get you a pressure switch for an indicator light.
HTH
Jim

[Cle Elum John]

Thanks Jim
Understand your confusion, I was not precise with the language.

The oil pressure appears to be an aftermarket sender and and probably an original gauge. It is electric. I say "appears to be an aftermarket sender" because it looks a little odd. It has a screw down ring terminal connection and is not on the original wiring harness. I said "probably an original gauge", because it looks like gauge in the operators manual. I don't know much of anything other than that.

Since I wrote the original request, I have decided to measure the oil pressure in the system directly using method in section 60-5 of the shop manual and adjust if required before proceeding with a replacement gauge.

The coolant is an obvious matched after-market gauge/"mechanical sender" pair. It is a bulb type sender which is mechanically clamped into an adapter which is threaded into the head. I don't know if the adapter that threads into the head is original or after market but the threads did measure to be consistent with 1/2npt. It is hard to get a good measurement.

On both the coolant and oil pressure gauges I intend to replace with all electric gauges/senders and set up a idiot light common to both gauges. I am looking at VDO brand gauges matched to VDO the senders. I doubt the original Deere gauges and senders are available. VDO has a wide range of parts available. I think I can get stuff that fits.

Thanks for help, you did verify that sizes of the threads on the block and the head and that they were not straight threads or BPS. This has bitten me in the past on other projects.

Thanks for the help and taking an interest.

John