TR6 Temperature Gauge

[BierRunner]

Here is a new dumb question. Does the temperature gauge impact the operation of the engine or is it simply providing information to the driver?

 

[GilsTR]

The gauge SHOULD be reporting the water temperature in the engine & radiator.
Knowing this water temperature is very important to the driver.
If your water is not warming up properly.... the engine usually will not run correctly.
If the water gets above normal operating temperature the driver needs to be very careful.
Possibly pull over before your engine overheating occurs.
Lastly if the needle heads to the upper end... disaster can happen.
I try to keep a close eye on the temp and oil pressure gauges.
Sorry for a long answer... no gauge it’s self does not effect the engine running.
But the temp of the fluid may.
Gil. NoCal

 

[poolboy]

Here is a new dumb question. Does the temperature gauge impact the operation of the engine or is it simply providing information to the driver?

I'm curious as to why you asked....is something funny going on ?

 

[BierRunner]

Yep. Had my TR6 out yesterday for a nice jaunt around central Ohio. Car was just back from the shop and running really well. After a few hours I returned home and later in the day my son asked for a ride. Took him around town and I started getting a stumble while accelerating at lower speeds. At the same moment, I noted that the temperature gauge was not working anymore. Was wondering if there is a connection.

I have spent the morning researching dashpots as the shop indicated that they had topped off the rear dashpot as it had gotten low. I wonder if there is a leak and that during my morning drive it was full and by afternoon it was low. However, not sure how to tell how full they are. Both look empty to me. How high is the oil supposed to be?

 

[charlie74]

The dashpots can leak if the bottom o-ring isn’t sealing properly. The level is easily checked by unscrewing the little black cap (mine are black anyway, i think some might be tan in colour) and lifting out the rod. You’ll notice a thicker brass (?) collar on the end and that provides the resistance for the air valve to move up and down by restricting the flow of oil past it in either direction depending on throttle position and vacuum vs the internal spring. I believe the capacity is something like 3 cc’s but there is a little weep hole at the base of the stem so the level can be self correcting if overfilled. Make sure that hole is clear. The weight of oil can be important as if affects how quickly the air valve moves. Some prefer a light oil and some heavy. I use the same weight of oil that is in the crankcase (20/50) but that is my preference in my carbs.

Poolboy (Ken) is the expert on ZS carbs and I’m prepared to be corrected if any if the above isn’t correct. Many have had their ZS’s rebuilt by him to great success which might be worth investigating.

As far as the engine temperature goes, make sure your gauge is displaying correctly. Maybe borrow/buy an IR gun and check your head temperature when it’s at operating temperature and verify your thermostat opens and closes. Check that the connection to the sender is good and clean.

Dashpot tops (edit: the pot on the right is oriented incorrectly; it should be 90 degrees counter clockwise…)

temperature sender connection below the thermostat housing (the spade connection on the right):

another view:

 

[poolboy]

Thanks for the endorsement, Charlie.
Regarding the gauge..see if the fuel gauge is working normal...the temp gauge and the fuel gauge have a common power source.
In the Bentley manual there is this illustration showing how to check damper fluid level...which btw is only 3.5 ml (cc) from empty to proper level...I wrote that because I know some unfamiliar will try to fill up the air valve, not the damper well.

 

[BierRunner]

The dashpots can leak if the bottom o-ring isn’t sealing properly. The level is easily checked by unscrewing the little black cap (mine are black anyway, i think some might be tan in colour) and lifting out the rod. You’ll notice a thicker brass (?) collar on the end and that provides the resistance for the air valve to move up and down by restricting the flow of oil past it in either direction depending on throttle position and vacuum vs the internal spring. I believe the capacity is something like 3 cc’s but there is a little weep hole at the base of the stem so the level can be self correcting if overfilled. Make sure that hole is clear. The weight of oil can be important as if affects how quickly the air valve moves. Some prefer a light oil and some heavy. I use the same weight of oil that is in the crankcase (20/50) but that is my preference in my carbs.

Poolboy (Ken) is the expert on ZS carbs and I’m prepared to be corrected if any if the above isn’t correct. Many have had their ZS’s rebuilt by him to great success which might be worth investigating.

As far as the engine temperature goes, make sure your gauge is displaying correctly. Maybe borrow/buy an IR gun and check your head temperature when it’s at operating temperature and verify your thermostat opens and closes. Check that the connection to the sender is good and clean.

Dashpot tops (edit: the pot on the right is oriented incorrectly; it should be 90 degrees counter clockwise…)

View attachment 82064

temperature sender connection below the thermostat housing (the spade connection on the right):
View attachment 82066


another view:
View attachment 82065

Okay, this picture was super helpful. The wire had slipped off. I crimped it a little with pliers and slid it back on. Viola! I have a temperature gauge again. Thank you!

 

[BierRunner]

I added 20W-50, which is what I am running in the engine, to the damper dashpot. I clearly overfilled as it was hard screw the cap back in. At least, however, I overfilled them both by the same amount. Took the car for a spin and the stumble is gone. You all are two for two! Can't thank you enough.

I must think on whether I want to try and fix the o-rings. I watched a few You-tube videos and people seem to use repurposed bolts and other things from the shop to get it done (not things one can buy). The necessary tuning after reassembly also seems like an advanced maneuver. Perhaps, I'll just go with vigilant topping off for a while.

 

[charlie74]

Very good! Glad to be able to help.

There should be some resistance when the damper is reinserted into the top of the carburettor if there is oil in it. As Poolboy’s post described, if the level is about right you’ll start to feel the resistance when there is about 1/4” gap between the bottom of the threaded portion of the cap and the top of the carb…

Most of what I’ve learned about these carbs is due to years of reading his posts. Search to your heart’s content, there is a wealth of information on this forum. Happy reading!