MFI Thermostat Cleaning...

[justacoupe]

I have followed carefully the instructions and tips at this link:

MFI thermostat questions

I have also looked at other threads related to the thermostat. Before I put it back on the pump, my question is regarding lubrication. It would seem that some sort of lubricant on the rod that facilitates its movement and the movement of the discs would be helpful. But... I cannot find any mention of lube, just the cleaning and reassembly.

Did I miss something or is it correct that everything inside should be clean but not lubricated in any way?

[Rot 911]

You want those disks and the rod to be clean and dry. Keep in mind that hot air is blown over the heat exchanger and then up through a hose to the thermostat. Any kind of lubricant will pick up the dust from that air and lead to the disks sticking together or sticking on the rod.

[justacoupe]

Thanks, Kurt. Makes perfect sense and completely explains why lubrication isn't mentioned. I appreciate the help!

[HawgRyder]

At best...you might try dry moly powder...like the type used in locks.
It gets everywhere...so be advised...use gloves!!
Bob

[Peter Zimmermann]

I've done hundreds of those thermostats, and I always put a very light smear of Bosch distributor cam grease on each end of the rod, but assembled the discs dry. Never had one come back, did most of them a second time, a third time, a fourth time, etc...at on-going, subsequent, major service intervals.

[dicklague]

this does not answer the original question, but I have found the best way to service the thermostat is to remove it and replace it with a long 6 mm screw and a new cover plate.

When the thermostat is warm the shaft is all the way in.

I live in a warm climate and was happy to get rid of the dumb thermostat. The screw lets you adjust the mixture overall. I have an AFR instrument [a Daytona-Sensors] and can fine tune the mixture with the screw.

For cold starts I have a push button on the dash that connects to a relay near the fuel solenoid in the rear. I couple of presses of the button squirts fuel into the throttle bodies.

I don't miss that thermostat at all.

At first I used used a screw and lock nut







Next I installed an indexing lever. If I need it richerI just move it a half turn counterclockwise.

[dicklague]

just to clarify, I set up the EFI carefully using the adjusting screws.

This adjustment was at full in during this tuning as it would be with a warm engine. Once I had the mixture really right according to the AFR instrument which reads AFR, MAP, and RPM and keeps 2 hours of data in its memory I use a Daytona Sensors WEGO IV sold by our sponsors here, then I could richen it by turning the screw out a bit. the richening is over the whole RPM range.

[justacoupe]

Thank you for all the input regarding the MFI thermostat. I have another question. This diagram is shown in a number of threads and in the MFI cleaning tech article:



While the diagram shows the gasket on the left between the shim and the housing, it does not show a gasket between the outer end cap and the housing. However, if you look at the first few lines of instruction for cleaning, it certainly sounds like there is a gasket at that point:

1. To remove the bottom screw on the thermostat cap, grab your air cleaner with your fingers while placing your thumb on the thermostat cap, remove top screw (cap is spring loaded).

2. Remove cap, set aside, (don't lose cap gasket, mine was broken so I made another one — this thing will not work without the gasket, it's also a spacer).


So, my questions are:

A. Is the diagram in error (e.g. not showing the end cap gasket)?

B. Assuming there should be a gasket between the end cap and the housing, my gasket was missing when I disassembled the thermostat. I can make one, but instruction number 2 makes it sound like the thickness of that gasket is critical. How thick should it be?

I appreciate all the help.

[Peter Zimmermann]

No gasket at the end cap. There is a rubber seal/gasket between the thermo housing and the pump, but you don't need to remove the thermo housing to do the service work.

[justacoupe]

Thanks, Peter. It seems that instruction #2 should be changed to eliminate reference to a "cap gasket".

Do you think he was actually talking about the "strangely shaped" gasket on the other end between the spacer and the thermostat body?

Regards,

Bill

[Peter Zimmermann]

Originally Posted by justacoupe

Thanks, Peter. It seems that instruction #2 should be changed to eliminate reference to a "cap gasket".

Do you think he was actually talking about the "strangely shaped" gasket on the other end between the spacer and the thermostat body?

Regards,Bill

Or maybe someone had been in that thermostat prior to the tech writer, thought that it needed a gasket, and made one. Along comes the next owner, sees the gasket, and thinks that it belongs there. Just a guess!