'68 Eldorado running hot

[mikanystrom]

Sigh, it's always something, isn't it?

Anyhow, my 1968 Eldorado has always been very well-mannered about temperature.  Under almost any condition, the temp gauge rises up to 1/4 and stays nailed there regardless of what else happens (as it should).

Well last week I was out for a drive and was accelerating on to the freeway... couldn't say it started exactly then but I had a strange feeling about "something".  In heavy traffic the gauge came unstuck and started to head higher.  Even in freeway traffic, it went higher.  Stopped after freeway driving, car starts boiling 30 seconds later.

Admittedly it was 100 degrees outside (or close to it) and I had been running the A/C on MAX all the way.  But I don't recall it used to do this.

The usual suspect, for me, is the thermostat.  I replaced it (it was marked 192 degrees and no idea how old it was) with a new 180.  Took the radiator out and flushed it backwards with a garden hose.  Flow was good... no problem getting all the hose water through it!

It runs as it did before in every other way.  Timing is set to 0 BTDC/ATDC so it doesn't ping, ported vacuum.

I have an electric 12'' fan that is hooked to the A/C compressor clutch circuit, so that runs when I have the A/C on.  But I'm thinking... either the water pump or the fan clutch?  The only way I ever had a water pump fail was the bearing blew and water/steam gushed out, and that's not happening.  Not sure how to check the fan clutch.. I feel resistance turning it.  It's a thermostatic type (I saw that when I had the radiator out).

Car has 50K miles on it but obviously it's 48 years old. 

Any brilliant ideas?

[Julien Abrahams]

The thing that I noticed is that your timing is at 0 degress. Is that not way too late? I don't know about the 472, but the 429 needs 5 degrees BTDC. Just a thought.

[Jeff Rosansky CLC #28373]

I say this on all posts like this. Start simple. You did a lot of work, but didnt replace the cap.
I did my entire engine and replaced everything I could find...... But I also forgot the cap.
Throw a new one on even if you think the old one is good.
Again, I made the same mistake.
Jeff

[Scot Minesinger]

The timing on a 472 is not 0.  My 1970 DVC or SDV is 7.5 on 472 engine.  Understand that timing varied year to year slightly even on same engine (do not have 1968 shop manual handy, but have set timing on a 68 once).  Plus it must be set with car in drive, foot on break, specific rpm and distributor vacuum actuator disconnected and plugged (that is probably same as your 1968 472).  I did some engine work on my 1970 Cadillac once and drove it after and it ran very hot (have an Autometer temp gauge).  After resetting timing it ran way cooler.  Another indicator timing is wrong is that the turbo hydro-matic trans does not seem to shift as smooth.  Timing is a significant contribution to overheating if not set correctly.

You wrote that this just started and maybe timing did not cause it.  Verify car is set to factory specifications for timing and start there.

Jeff is right if cap will not hold pressure, then car could easily overheat because pressure cap raises boiling point of coolant by keeping the pressure at 15psig or so (two atmospheres approx.).  Also, if the radiator has a very minimal leak, pressure can be released having same effect as bad cap.  This happened to me on the 1985 307 Olds engine.  Olds 307 overheated no matter after checking all things, replaced original radiator and all was good.

Hope you find the problem quickly and get to enjoy the remainder of the season.

Thanks,

Scot 

[TJ Hopland]

I too think most likely place to start is a lack of cooling system pressure issue.   Under the conditions you describe I would say 220-230 would be a reasonable coolant temp.  At 16psi and 50/50 you should be good to the 260 range the lower the pressure the lower the boiling temp.  If you don't have any pressure you are going to boil around 212 which obviously does not give you much headroom over the 200 ish normal operating temp.  There may be other issues causing higher than usual temps but the lack of pressure is what caused the boil over.   Sounds like the same thing happened to one of the cars in our fleet over the weekend except I was not there to see what the gauge may have been doing or to verify it was coming out the bottle.    Topped it off and drove it back home with no issues but its not building pressure so I think there is a radiator pressure testing kit in my near future.   

If you mess with the timing be sure to take before readings at various rpms and vacuum settings just so you can get back to where you are now if it turns out that its the best spot.   I'm not thinking the timing is the issue. 

First test dead cold take the radiator cap off and make sure level is correct.  Reinstall cap and give the upper hose a squeeze to get a reference what it feels like with no pressure.   Start er up and let it warm up.   During the warm up keep feeling the upper hose for pressure and temp.   There should be no pressure build up till you start to feel some heat from the stat opening.  If you feel pressure before it gets to or at least close to full temp you may have a head gasket issue which is not common on these engines. 

Once the stat opens you may or may not feel some pressure building.  Sometimes it takes a test drive, just a couple miles should do it.   After that upper hose should be pretty firm to hard.   If its not there is a leak somewhere. 

For the fan clutch the quick test fully warmed up is to open the hood and position yourself so you can get one hand on the key and see the fan (or get an assistant) and see how may turns it makes after the engine stops.  Less than 1 turn is a good sign.  If it makes several turns its shot.    If you have to replace it get a 'heavy duty' or 'severe duty'  model,  those come on sooner and get to a higher speed than the standard ones.

[R Schroeder]

Retarding the timing on a car will make it run hotter. Seems to me running at TDC, will create all sorts of problems. Cars had ported timing for this reason in California. To make them run hot.
Nothing like direct vacuum, and at least 5 to 10 degrees before top dead center. Set timing with vacuum advance plugged. Once timed, then plug vacuum back on vacuum advance. Using a vacuum gage your engine should pull 21 inches of vacuum , at idle, with this set up.
That's my 2 cents, and I'm sticking to it.
Roy.

[R Schroeder]

Just found this. It may help......................

http://www.rootesparts.com/id201.htm

[Kell Oskarsson]

According to the workshop manual, the ´68 472 should have timing set at 5° BTDC, with idle speed set at 550 rpm with transmission in Drive, and with distributor vacuum advance as well as vacuum parking brake release hose plugged.

Also make sure your carb isn´t set too lean.

[Scot Minesinger]

All good posts, set the timing and see what happens after that.

[TJ Hopland]

FWIW I could not find any issues with the car that burped over the weekend other than it was not holding pressure.  I could not find any leaks.  Went and spent decent money on a pressure testing kit and found it held pressure just fine and no leaks which leaves the cap.   $6 new cap and it seems happy again.   I should have tried that before buying the tool but at least I have one now.  It will be nice searching for future leaks on a cold engine. 

[mikanystrom]

Lots of advice!  Thanks everyone!!  Will track down one thing at a time.

Reason I retarded the timing to 0 (well maybe it's 1 or 2) is that I just couldn't get it to stop pinging even at 5 BTDC.  Of course I know they belong between 5-7.5.

And I tried to run one of these off manifold vacuum once, couldn't get a stable idle at 550 per spec.  I emailed Cliff Ruggles (the Quadrajet guy) and he suggested that the throttle would be basically completely closed on manifold vacuum, so use ported instead..

Hmm... "your mileage may vary"?

Anyhow, lots to do.  Yes last time I had a "boiler" it was fixed by replacing the thermostat and the radiator cap...

[The Tassie Devil(le)]

If your engine is pinking at such a small amount of advance, then you are running really crap petrol.

Or, you have another problem, like carboned-up combustion chambers that are holding excessive heat and have hot spots that are igniting the fuel mixture well before TDC is reached.

What are your compression readings at cranking?

Bruce.

[Bobby B]

Hmm....10.5 to 1 compression on today's fuel is a tough thing, but shouldn't be an issue if everything is working in harmony. All good advice in the above posts. Lean burning at that high a compression ratio will cause to car to overheat immediately when under load. Your timing is WAY too retarded and overheating is inevitable. Compression check, cooling system, ignition system, tune-up to spec, etc. need to be done. Was anything changed just before the pinging started? I would've thrown a can of octane boost in there just to see if the pinging disappeared. I've run 9.5/10 to 1 modified Pontiac 400 motors on Today's Premium Ethanol with no problem at, or even a few degrees, above factory advance spec with no detonation. But again, all systems in top spec including fuel to air ratio, ignition system, and cooling system. I would also be looking to see where my burn is with an exhaust sniffer.
                                                     Bobby

[The Tassie Devil(le)]

I am running my '72 with '70 Pistons, .040 oversize, and planed heads, and only the slightest of pinking with standard Unleaded fuel.   We don't run Ethanol stuff down here.   Well, we do, but we don't have to buy the stuff.

Bruce.

[DeVille68]

Possibly wrong spark plugs that run hot and ignite before the piston has complete the compression stroke. Check the type (heat range) and cap of your spark plugs. Maybe this helps with the pinning problem. I have a HEI ignition, so I am using different spark plugs than stock.

[mikanystrom]

All right... I am now having the same problem with my '70 convertible (overheating).  They do have the same engine, more or less...

Now I never really used to drive these cars in very demanding hot weather with the A/C running before (heck the A/C didn't even work), so I *am* putting more heat stress on them than I used to.

So I set the timing to 0 for a reason.  The book (shop manual) says you can retard the timing if you are having pinging issues, but not beyond TDC, so that's what I did.  I recall that with the gas we have today here in California vs. what was available, timing at 0 A/BTDC should be "about right".  But it's not.

In any case, I think the gas changes since the late 60s are substantial enough that I can't just follow the tune-up instructions and have it work properly.

I have a Crane Cams advance kit in my distributor so I can make lots of adjustments to the timing curve if need be.  So let me start with what CANNOT be adjusted.

If I get in the car, put it in drive, and put my foot to the floor, let it accelerate at WOT to the upshift, I cannot do anything about the advance that I get at 4200 rpm or whatever the shift point is.  Also the idle screw mixture is basically doing nothing at the upshift.  So everything has to be based off what happens at that upshift.

Even at 0 TDC, I get pretty severe pinging in the 1970 De Ville at the upshift, and also in 2nd right after the upshift.  Which suggests the timing needs to be retarded further..  I don't see anything that can be done to cure pinging at the upshift other than retard the initial timing? 

And the stock spark plugs are AC 45s.  I believe the "5" means VERY HOT...?  (4 means 14mm).   I could reduce the heat range to 43s?

Stock my cars have heat-operated valves to switch from ported to manifold vacuum when they get hot.  But does that really help much?  Yes, it means they run more efficiently, but the idle r.p.m. also goes up!

I like the throttle response with ported vacuum, you really only need to touch the pedal to "go".  But of course if that is making the car overheat at idle then I can try to go to manifold vacuum.

Should I connect the distributor vacuum can to manifold vacuum and time the engine for 7.5 BTDC with the vacuum advance connected?  I've always timed the engines with the vacuum advance disconnected.

Ahhhhh that might actually work.... manifold vacuum, 5-7.5 BTDC.  That means basically maximum vacuum advance at idle.  Or do I want even more advance at "high vacuum" (light load, 2000 rpm)?  I can adjust that too using my adjustable vacuum can.

One thing I've had to do is limit the range of the vacuum advance.  The can is capable of 30 degrees of vacuum advance.  I run about 14 (which actually meets up pretty well with what the book says).  I can change the springs on the distributor advance weights but I don't see what that will do if I'm getting pinging at 4200, the full centrifugal advance ought to be in by then, I'd think.  Right??

Does anybody have a nice summary of a combination that seems to work for one of these engines on modern gas?  1968-1970 472 with 10:1 compression.   Initial timing, ported/manifold, how much vacuum advance, how much centrifugal (if you modified the distributor to change that), and if you know... the rate of vacuum advance and centrifugal advance?  What heat range plugs?  (Who keeps track of all those numbers?  Cadillac-La Salle Club members, maybe??)

[TJ Hopland]

Didn't 70 call for a 44 plug?  I was thinking the 45 came later on the lower compression engines.

Good call on the adjustable vac can, most of the stock replacements seem to be a one size kinda fits all sort of a thing with way too much range in em which usually leads to pinging at cruise which leads people to dial back the base setting which then kills the performance. 

Most of the stock Cad specs I have seen the mechanical is all in around 2000.   Even the hot rod guys that are spinning them faster I think are all in my 3000 so you would seem to be in the range. 

When is the last time this engine was apart?   Maybe you got a carbon build up or some nasty sharp edges that are holding the heat?

Timing chain is good?

[Scot Minesinger]

mikanystrom,

I have a 1970 Cadillac and after the valve job timing was set to 0 and it ran way too hot.  I checked timing, reset to factory and it runs perfect.  Drove the car yesterday and today when it was 98'F (105'F heat index) and my accurate temp gauge read 208'F even idling for three minutes at a stop light.  Mine is a convertible so top was down and a/c off.  A/c raises temp about 5'F, so 213'F would still be OK. 

Timing needs to be as close to the factory setting as possible, ideally 7.5 degrees.  I use premium unleaded standard pump gas from any station, no particular brand.  You cannot use regular.

On a 1968 where it was pinging I set the timing back 1 degree and that cured it.  A timing retard of 7.5 is way too much for my car.  Compression ratio is a little higher on a 1968 Cadillac than a 1970 472 engine.

[mikanystrom]

Scott is that 7.5 BTDC with the manifold vacuum hooked up? Or vacuum disconnected when you set the timing?

[mikanystrom]

Also, shop manual says R-46-N for the plug, .035 gap.  So even hotter than I thought...

I have a Pertronix (on all my cars).  So that might change the requirements for the plug.  I figure the gap could be .060 at least.  Does it affect the temperature range too?

TJ, the engine on the De Ville was apart recently.  Head job including valves.  See another thread about the camshaft.  Brand new timing chain (Cloyes).  Cam is timed slightly advanced from spec (~2 degrees, closest I could get it).  Inside of cylinders is very clean...