Thermostat/Cats

[SHOMurph]

Just bought a 93 SHO with 70k and bad thermostat.

Do I need to worry about the catalytic convertors being bad due to the thermo?

I've read that bad cats from bad thermos can cause engine damage....also heard that was not so. Need helpful info please!

Thanks, New SHO Owner and Luv' it!

 

[LOUDSHO92]

Wht the thermostate controls is the flow of water to cool your engine. When it doesnt work properly your engine can overheat and be destroyed. I saw it ona Suburban. The 3 cylinders were toat all due to that one part. So no your cats wont be affected but your engine could.

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92 White SHO
HiRevs Competion Clutch
SHOSHOP Engine Mounts
Koni Shocks
StrutTower Braces
UD Pullies
Awesome Sound System

 

[fredhurderjr]

That's not exactly true. With the T-Stat stuck, the EEC doesn't operate in closed loop; it's running rich all the time. The extra fuel eats the catalytic brick & leave a sandy deposit in the cat housing. The when you wind it up & let off, you can suck the sand into the engine.

That's, uh, bad.

Remove the Y-Pipe & check for this condition if you're worried about it.

 

[fricker66]

Welcome to the board SHOMurph! I had a similar post last week and was told that there's no way the engine sucks debris back into the combustion chamber. Not being a mechanic, I can't offer any real advice but like Fred mentioned, if you're worried about it, check it out and make an excuse to buy a Perf. Plus Y-pipe.

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Frederick Ricker
89 Black/Grey w/ 80k mi
91 Slicers, 190lph pump

 

[MeShoHorney]

Originally posted by fredhurderjr:
That's not exactly true. With the T-Stat stuck, the EEC doesn't operate in closed loop; it's running rich all the time. The extra fuel eats the catalytic brick & leave a sandy deposit in the cat housing. The when you wind it up & let off, you can suck the sand into the engine.

That's, uh, bad.

Remove the Y-Pipe & check for this condition if you're worried about it.

Fred, I know this is wide known about the SHO but I don't understand how the sand from a melted cat could get into the engine.

Given, during the exhaust stroke the pulses of air coming out of the engine would certianly not allow for air to be sucked in when the exhaust valves are open.
When you let of and it's at the intake stroke the exhaust valves are closed.
Does this happen during the overlap??

Never really made sense to me.



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Jason

'91 Red |Pseudo + Edition|
Mods? Yeah, I got some! SHOracing.com

 

[SHOTIME]

As I see it. Its looked at as one of two things.

A: An urban myth. Take it as you want.

B: this actually happened to someone, there for, it is as widely known as it is now.

Personally. I wouldnt take the chance for the ?what? 30 minutes it takes to drop the Y-pipe to inspect the cats?

Just good insurance.

I ran with a bad T-stat for a while on the winter beater. till it got cold enough for me to complain about the lost of heat.

Course I then used the reason to buy a Y-pipe and stick it on there too.

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Eric
mailto:[email protected][email protected]</A>
My Web Space
New England SHO Specialists

 

[sdpatt]

Is this the same Murphy that just inquired about a valve gapping job? As said before, the problem with the thermostat is that it doesn't completely close. This causes the engine to run below the normal operating temperature and as said, the engine control does not ever get into the closed loop mode. This runs the engine rich as if it were constantly in warm up mode. This rich mixture over time can overheat the cats and damage them.

If the thermostat sticks closed, the engine will overheat. This causes much more damage than would be done to the catalytic converters. Ask Jeremy Hohn about his new heads. Very expensive lesson.

Regarding the cat dust getting sucked into the engine. With the 3.0L engines that have no EGR, I believe this is physically impossible as the exhaust flow is always out of the cylinder through the open exhaust valves. Now the engines with the EGR, there is an open path from the number three cylinder's exhaust manifold to the intake manifold. This can theoretically provide a path for the cat dust to get back into the engine. However, even when the throttle is closed at high rpm, there is still some bypass sir flow through the IAC valve into the cylinders. The engine is still acting like an air pump with the flow always out the exhaust ports. It's not as hot or as voluminous as when under power, but there is still airflow out the exhaust to move any cat dust out the pipe.

I killed a set of the SHO Shop Y-pipe's cats several years ago and my engine is still kicking. Hard!

Scott

 

[94ShoOff]

Whats with Fords crappy thermostats? I had to replace all three within a two month span. The first two were partially stuck open, while the third had a bad outer seal. At least they are easy to change.

 

[Jeremy Hohn]

Yep, don't mess around with bad t-stat. It caused cracked heads on an overheat and a repair bill of over $2500. Good thing I had used car warranty at the time. Easy to change, and I suggest you do so quickly. Make sure jiggle valve is up, and your gasket is seeded properly around the t-stat. Good luck.

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Jeremy

1993 atx 126k miles
ENGINE:
-SHOSHOP underdrive pulleys
-SHOSHOP cold air induction
-SHOSHOP 80mm MAF
-Ted Breaux LPM
-Performance Plus y-pipe
-SHOSHOP catback exhaust with Magnaflow chrome tips
-Redline Water Wetter
-fresh 60k (SDPATT)
TRANNY:
-Rebuilt 94/95 axod tranny with trans-go kit and Redline Type 3 ATX fluid
BRAKES:
KVR cadmium plated and cross drilled rotors with performance friction pads
APPEARANCE:
-Colgan hood cover with SHO lettering
-Lund blackouts front and back
-Cincysho white face gauges
-black body filled s-h-o lettering
-Blazer fog lights
-PIAA high output headlamp bulbs (fratperformance.com)
-fish-tank bulbs installed
-wclewis "powered by yamaha" black badges