warm running device thermostat

[stickandrudderman]

I've has some air slides that leak, allowing a constant bleed even when fully closed. A coating of copperslip usually seals it up but the treatment needs to be re-applied at every service.

[twistedtree]

Adding round shims is my plan.  Thanks for the confirmation that's the right approach.  I tested the device when I had it apart and it seals nicely as long as the plunger is down far enough.  I had also measured how much plunger movement was needed to close the valve, and measured the throw of the heat feeler and it measured out to be just enough to close the valve, but apparently I was off just enough to not get full closure  This time I'll test the whole thing fully assembled before refitting to the car.  All this draining and refilling the cooling system is a pain in the neck.

[wwheeler]

To keep the WRD thermo housing from leaking everytime I remove it to adjust the shims, I used a Permatex product and it worked perfectly. This is NOT like a standard RTV silicone. It is much, much tougher.
 http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_Permatex_Ultra_Grey_Rigid_High-Torque_RTV_Silicone_Gasket_Maker.htm

I probably took the housing off 10 times and it never leaked. I spread a thin ribbon of the "Ultra Grey" sealant on the beveled contact face of the thermostat bulb. I then placed the thermo bulb inside the housing and used the seating washer to mash it and make sure it was straight. I spread the excess around the bulb leaving a small bead around the bulb. I just let that sit overnight and it is done.

In fact, I just removed the bulb from the housing last week so I can plate the housing. The sealant was in great shape after two years and was somewhat difficult to remove. I will use the Ultra Grey again when I reinstall.   

[Rhodrich]

Sorry to drag up an old thread....

I have what seems to be a common problem with my '68 280SE in that the engine runs far too rich on the warm-up cycle.  I tried following the advice here by taking away shims from below the WRD, but on removing the bolts, there don't appear to be any there.

The engine runs fine once it is warmed up, and although it runs very rough when cold, it starts without a problem.  I know the WRD is working, as I can hear the air rushing through it when the engine is cold, and the engine has a high idle speed that reduces once the engine warms up.

I have checked the linkage to ensure that it is within spec.  I've also checked that the cold start valve is not leaking.

Does anyone have any ideas what to look for next?  It's more of an annoyance than anything else, as once the engine is warm, it all runs perfectly. 

Thanks

[stickandrudderman]

First you need to confirm that the mixture is in fact not overly rich when the engine is warm. It might well be running fine but that doesn't mean that the mixture is correct.

[wwheeler]

What Stick said and:

The WRD air filter may be highly restricted.

Make sure the shims aren't stuck to the bottom of the housing. They are typically very thin , .003" to .020".

I suppose the thermostat rod could have worn enough not to need shims, but that seems unlikely.

[Rhodrich]

Thanks - will have a look again for the shims.  It's a possibility I didn't spot them.  I'll see if I can remove the air filter on the WRD.  It does seem to be letting air through though, as it makes quite a loud sucking sound. 

I don't have a gas tester, so can't really tell whether it's running rich when it's warm, but I've pulled the plugs, and they're a nice brownish colour, so I'm guessing its OK.  That said, it does kick out a bit of smoke when I floor the accelerator.  I have checked the linkage according to the 'linkage tour', checked the ignition timing, and adjusted the valves, so I'm running out of things to check.  The car has only done 80,000 miles from new, so I'm thinking it unlikely that things will be that worn out.....

The most annoying thing about this problem is that I only have about 10 minutes to do any adjustments before it warms up.

[wwheeler]

You can check the mixture by doing the split linkage method. I use it all of the time and works well hot or cold, for idle or higher RPMs. Do a search for split linkage and you should find it easily.

If you get the air filter off using a thin wrench, you can do a simple test to determine if the filter is too clogged. Again, do a search and you should find it. There was a post recently about that.

I learned these things along with 10,000 other things on this site. Join and become a full member. It is well worth it!

[Rhodrich]

Just to update (by dragging this thread up again).... the rough running when cold turned out not to be anything to do with the mixture in the end - using the 'split linkage' method I ruled that out.  I also made sure the WRD air filter was clean.

The problem sorted itself out after I took the plugs out to do a compression test (which was fine), and cleaned them with a cloth before putting them back in - they were a bit fouled.  I've now changed to NGK BP6ES plugs from the wrong resistor type ones that were in there, they haven't fouled since, and the car runs smooth from cold.  I did a 400 mile trip the weekdnd before last, driving the car hard (cruising at 80mph), and it's running better than it ever has since I had it. 

Moral of the story - correct spark plugs make all the difference, and these cars like a good run once in a while.  The advice from this site has been invaluable though - you're right - I really should become a member!

[Benz Dr.]

The BP6ES  NGK plugs cross over to the old W7DC Bosch plugs that are no longer available. I found that W7DC plugs were too cold for most aplications so I witched to W9DC. Now that they're also no longer available, I now use BP5ES which are closer to the old W9DC. These slightly hotter plugs seem to work better by heating up faster during the critical starting and warming up period.
In short, I don't even bother with anyting but BP5ES plugs now.