77 L-48, stock except intake, headers & Lars dist. advance kit.

OK, here's my problem!!!

Last year it wanted to run a little hot during hot weather. (180 deg thermostat).

So early this spring I flushed the radiator, new 180deg thermostat, and added new A/F. Took car to Knoxville expo in the spring, no problem. Summer arrives and it's getting up to about 200deg. Harmonic balancer separated so while changing that we discover the water pump is leaking at the weep hole. (Ah-Ah, high temp problem will be fixed)! WRONG!! Changed har. bal., water pump, timing chain, upper & lower hoses, checked 180 thermostat, (working fine), put it back in, added new A/F again.

Tuesday, 7/3/07, 5 miles from home, on interstate, temp goes to 230 and spark knocking from hell. Lower the timing, seems to be better, but during the heat of the day it still goes to 210+. Still spark knocking, lowered timing some more! So, 7-6-07, I change to a 160deg stat. Today, still getting to200/210!!!

WHAT ELSE CAN I DO???? OR WHAT ELSE CAN IT BE???

ANY SUGGESTIONS AND HELP IS APPRECIATED!!!

 

Is it overheating at low speed or highway?

If highway...do you have the chin airdam installed?

If around town...how is your clutch fan working?

What is your max total timing all in?

 

Make sure that your fan shroud seals against the radiator support snugly. Purchase some soft tubular black rubber pipe insulation and some weatherstrip adhesive, make seals from it and seal up any gaps between the shroud and support. Also check the top of the radiator support. Is there a seal there to stop air from flowing over the top of the radiator? If not, use some more insulation and make one, or you can get the seals from Doc Rebuild.
Another item to check is the lower radiator hose. They are supposed to have a spring in them to prevent them from collapsing at high RPM's, the water pump can suck them shut, like a drinking straw collapsing.
Another frequently recommended solution is to drill a 1/8" hole in your thermostat to prevent air from getting trapped in the cooling system.
I hope that helps!

 

Great points. Many people dont know about the spring when replacing the lower hose which is typically thrown away with the old hose.

 

One more thing.

Our temperature gauges are notoriously innacurate. Shoot the engine with an I.R. temperature gun to confirm what the "true" temperature is. My gauge reads about 20* higher than it should.

 

Car has Pace Car spoiler!
Clutch fan working.
Max timing about 34deg, haven't checked since droping timing.

 

All seals & insulation is in place.
No spring in lower hose for years. But has new hoses.

 

I'll try this!

Could the sensor be BAD????

 

A good thing todo but remember that you had another sign of overheating with the spark knock.

Pehaps your new hose colapes easier than the old. Dont rule out the sping yet. After it happens again pull over and look at the hose when reving the engine.

Did you recently install the pace car spoiler?

 

If you can hear engine knock, you are running hot!

I would replace the spring in the lower hose and have the rad checked to ensure there are no blockages.

 

I'll check the hose tomorrow.

Spoiler has been on for 25+ years.

 

Can you still buy the springs??

 

Hopefully someone will chime in with a part number for the correct replacement hose that comes with the spring.

 

Just a thought - are you filling the radiator and engine, then just going out for a drive? You need to make sure to "burp" the system to get rid of any air pockets. When the engine is running at idle, can you grab the lower hose and feel the coolant flowing through it? Are there leaves and junk blocking the front of the radiator? Was this at highway speed or sitting in traffic?

(Adding a lower temp thermostat won't help cool the engine if the system isn't up to snuff - the thermostat will just open sooner.)

 

All hoses in the aftermarket now, dont come with a spring. We are told the way there manufactured now , there not needed.
If some original hoses are still out there, that might be the only way to get the hose with the spring.

 

Had a friend of mine who owns a garage check this on my car and found this to be true. Not as high as 20 degrees, more like 10.

 

couple of thought here. A, that rad. is 30 years old,might be a bit of debri in there. B, make sure the A/F types were compatablr with one another. It will look milky with "clots" in it if it isnt. C, sometimes ,one can run the heater on high to expell a bit of heat,,sometimes just enough to bring that needle down. Good luck.

 

It's the radiator.

Either have it rodded out or get a new one.

 

first of all, get rid of the new 160º t-stat and put in the correct 180º one. The 160º will do NOTHING to affect max operating temps, only minimum operating temp.

Also, I understand the desire to retard back the timing because of knocking you hear when it gets hot, but the more you retard the timing the hotter the operating temps will get. Timing that is retarded causes the motor to run hotter. The problem isn't the timing, the knocking is a because of running so hot - fix that issue and your knocking will go away.

Obsolutely replace the lower rad hose with a correct one with the spring in place - lots of vendors carry it such as DeWitts, Paragon, Dr. Rebuild, etc.

If you have ALL radiator seals in place, the fan clutch is working properly, lower spoiler/airdam in place, timing is correct, and you have confirmed that you are really running hot with an IR temp gun (the temp senders and gauges are notoriously wrong) and you are truely running hot than the answer comes down to two things:
1. radiator doesn't have enough heat rejection capability - call DeWitts and order up a new aluminum radiator.
OR
2. still an unseen issue with airflow thru the radiator so check everything again from the seals, airdam, shroud, fanblade and fanclutch.