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Thermostat Confusion

M

major_tom

Regular Contributor
"Twin 1984 Crusader 454’s, Gen

"Twin 1984 Crusader 454’s, Gen IV, fresh water cooled.
Starboard engine temp. is 160F at idle and low speed, 180 at cruise.
Port is 140F at idle and low speed, 160 at cruise. I would like to see 160F here at low speed before winter layup.

Changed the port T-stat with a Crusader 160 degree T-stat. No change, port motor still at 140F. Cleaned the connections at the port motor sending unit, no change. Switched the sending unit connections at the gauges, port gauge now reads 160F and starboard gauge reads 140F, so gauges are good. Went to ebasicpower website and had a look at the T-stat housing:

http://bpi.ebasicpower.com/c/CRU2E/Thermostats+&+Kits+for+Crusader

Looks like there are two T-stats and upper and a lower one, which doesn’t make any sense. I replaced the upper T-stat near the figure 8 gasket with the new 160F Crusader T-stat and got no change.

Should I have put the new T-Stat in the bottom location where the housing mounts to the block?

Should I buy a new sending unit? The existing one looks like a resistive element that grounds to the block, and appears to be working."
 
"Hi Tom,

I have that same h

"Hi Tom,

I have that same housing on our 454's. I believe what you are seeing (and I could be misintpreting) but that other piece is a spring loaded plastic type of relief valve.

Having rebuilt both engines and glass beaded that assembly, I know of only 1 thermostat. Mine are both 160's and my engines do what your do....155 stb and 140 port"
 
"Interesting. Where are your

"Interesting. Where are your T-stats located, i.e. in the upper portion of the housing with the figure 8 gasket or the lower portion with the single hole that mounts to the block?

I should have mentioned that I do not have any provisions for a water heater connection to either engine."
 
"Old style FWC uses the RWC ba

"Old style FWC uses the RWC based, 4 hose complex thermostat housing assembly. And, two output plugs/covers. The new(er) style for FWC only is simpler, and does not need the output plugs, nor the relief valve. Both upper and lower therm housings are different part nos. Check your temps with a IR gun, and 20 degree change is normal from idle to cruise power settings."
 
"I have the old style, circa

"I have the old style, circa 1980's, just like in the link I posted. I am fairly confident that the measured temps. are correct, and I agree that a 20 degree rise from idle to cruise is normal. But 140 F is not normal operating temperature at low speed, and what I don't know is the proper configuration of the assembly. Maybe I am missing plugs/covers. I suppose I could take apart the other side but that's more work than I was looking for."
 
"After I blew out one of the p

"After I blew out one of the plugs on a far offshore trip, I converted all the cast iron pieces to the newer, simpler style. These are external caps, using hose clamps. I get 167 deg at cruise at the thermostat housing, with 160 deg thermostats (on both engines).
Also note that the gaskets have a brass grounding ring to provide ground to the temp sensor. The auto style doesn't have this feature."
 
"tom:

your checks verified

"tom:

your checks verified the gauges are consistent, not that the senders are accurate. The quickest way to verify the senders' accuracy is with the IR gun Dave mentioned.

The Brass ring (we call them grommets) Dave mentioned, in the gasket, is key to having accurate readings. Make sure it goes between the manifold and the housing.

If they are different, it should be straight forward figuring what to change.

If you don't have access to an IR gun, you can use an OHM meter on the sender(and a good ground). The OHM meter characteristics may limit your measurement accuracy.

Other item is to check for thread sealer on the sending unit. NO mfg endorses this practice though I can't believe a thin layer of teflon pipe dope will electrically isolate that size of pipe thread joint."
 
"Yes, I verified that the gaug

"Yes, I verified that the gauges work. The sender could be slightly off. I could switch them but would have to drain coolant from both engines, etc. Instead, I will make a careful temperature reading at the same place in the housing on both engines with an electronic probe. This will tell me if the temp. readings are true.

I have no idea what the brass ring or grommet is, or what it does for that matter. You say it goes between the manifold and the housing, i.e. down low, not up top. That part does not appear on the exploded view from the ebasicpower website. Maybe I'm looking at the wrong thermostat housing on their website but it sure looks familiar.

What's the part # for the brass thingy. Maybe mine is missing or broken.

There does not appear to be any sealent or teflon in use on the sender. I inspected it closely while I was cleaning the contacts."
 
"I have the old style housing.

"I have the old style housing. Can anyone tell me where to get the newer style? I have the same issue, with differing temps and chasing steam. Thanks, Mark"
 
"new upper: 97851
new lower:

"new upper: 97851
new lower: 97452

220393.jpg
thermo pic
 
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