Need some help....

[Chops442]

Ok, guys, I am really at my wits end with an overheating problem so maybe someone here has some insight. I recently wiped a lobe on my
lunati cam and replaced it in my 455 with a Mondello 22-25-10. The car has run very hot with an enormous amount of pressure in the cooling system intermittently ever since, and I cannot seem to track down the issue. I have:

*had the radiator dipped and flushed
*replaced the thermostat (twice)
*replaced the head gaskets
*Removed and inspected the water pump/impeller (all good)
*Checked the timing chain to ensure proper gear alignment

One day I'll get in and it will cruise between 170-190 degrees temp no problem, the next time I'll get no more than 1 mile from home and it will be approaching 220-240 degrees and boiling over. When I had the radiator dipped the guy at the shop said the tanks had expanded and said he thought it either had a blown head gasket or a stuck T-stat; it had neither. in hindsight it may have been running a bit hot before the cam change, but not to this extent. Ideas??? I am just hoping it is not time to grab the cherry picker....

[MichiganMuscle77]

There's always the chance that the overheating has nothing to do with the cam swap, it could very likely just be a coincidence.

Just be sure you've covered all of you bases, and it helps to diagnose the problem as if nothing has been changed with the motor. That way you can rule out other things and if it IS the cam swap that caused it, you'll know for sure.

Got air pockets in the system, by chance? Maybe try doing a full cooling system flush instead of just the radiator. The coolant is pumped through the system by the water pump which is driven by the pulleys, so the cam would only affect the speed of flow.

Try getting an electric cooling fan or even an electric water pump. If neither of those solve your problem, I'm going to guess there's something pretty serious wrong.

[Chops442]

All bases are checked; It's definitely not the fan or the pump. Pump is in good order (and switching to electric wouldn't make it cool better anyway), and the motor gets hot even when rolling downhill with fresh, cool air blowing through the radiator when fans have little effect or are shut off. Might try a full system flush I guess at this point, but again, that is really not going to do much and those are mainly designed to clean the tubes in the radiator. What I dont understand is that it is intermittent. One day it drives with the temp under 180, the next day the temp shoots to 240 within the first mile. ???

[zodiacblue442]

Another thing to check is timing. Retarded timing especially will make the engine run hot. Each engine is a little different but I set my Olds engines at about 14 to 15 degrees advance. That's for 5,400 ft. elevation, so down at sea level you'd set the timing at about 10 or 11 degrees advance. Strange that the heating problem is intermittent. I would have said an intermittent stuck thermostat also.

[7hurst4]

i had the same problem with mine after i rebuild the motor. i tried 3 different thermostats and still it would build up huge amounts of pressure before the thermostat would open. you have a air pocket in the engine... take the heater hose from intake to the heater core and the radiator cap off to let the air out. also make sure you have good flow from the intake throught the heater core back to the radiator. get rid of the heater control valve, its restricts the flow of coolant to much...

[MichiganMuscle77]

All bases are checked; It's definitely not the fan or the pump. Pump is in good order (and switching to electric wouldn't make it cool better anyway), and the motor gets hot even when rolling downhill with fresh, cool air blowing through the radiator when fans have little effect or are shut off. Might try a full system flush I guess at this point, but again, that is really not going to do much and those are mainly designed to clean the tubes in the radiator. What I dont understand is that it is intermittent. One day it drives with the temp under 180, the next day the temp shoots to 240 within the first mile. ???

Well the benefit of an electric pump is that even at low, lumpy idle, the water is flowing through the engine at a constant velocity, so couple that with an electric cooling fan and your engine should pretty much always stay at the same temperature.

All I've got in my car is an electric cooling fan, and even then the temp never climbs above 200 when I'm sitting still on a hot day after a long drive. Worth the money.

[Chops442]

I just flushed it out and drove it, same issue. I cranked it with temp gauge at 0, literally got 2 minutes into the drive and the gauge went to 260. Other than the heat, it cranks and drives fine.

Michigan, I hear you on the electric water pump/fans; I didn't mean to be dismissive. I just gotta think it should still run OK with a known good pump and my trusty flex fan that's been keeping it cool during these hot Georgia summers for 15 years. I have always wanted to try some push fans; how tough were those to put on?

I had in my head that there might an air bubble in there around the impeller or t-stat that's stalling the coolant flow. So, you removed the heater control, put in a fitting and ran that hose straight to the pump?? If so, that's my next move... Walk me through what you did. Thanks guys!

[Chops442]

And ditto on the air pressure....the hoses were rock hard....

[MichiganMuscle77]

Definitely, definitely sounds like air pockets in the cooling system. But if you just flushed it and it's still doing it... i don't know.

You're running 50/50 and not just water, right?

[Mikedinva]

Have changed your radiator cap? Had a similar problem years ago........

[Revots12]

I second that on the radiator cap ! Radiator caps can go bad 2 ways, they either wont hold pressure OR they wont bleed pressure beyond its prescribed setting causing all sorts of issues. Replace that cap !

[JPahl77TA]

Not sure here, but a good friend of mine had this same problem, freshly rebuilt Chev 396. He replaced everything to do with the cooling system and it still would overheat. It turned out to be his timming. If you say its Intermittent I would check the timming and also your vacume advance, Maybe its sticking. Just a thought. Good Luck! Jeremy

[Chops442]

Runniing 50/50, new radiator cap....

I'm going to replace the heater control with a nipple, bypass the heater core, and see what happens....

[rickman]

I had a similar problem on a car, few years back. Replaced and/or checked everything. Long story short, replaced the water pump and that fixed the problem. Pump appeared to be good but when it got hot, the impeller was slipping on the shaft. Seemed to be OK when I checked it but after replacing the pump, I checked the old one and with enough force, it showed it was slipping. Good luck.

[djb56]

Put a new radiator cap on it (14-18 lb). Check your top raditor hose. Another thing could be it is not idled high enough, Does it have air on it and are you running it at the time?

[oldsmeister]

Since you have a temp gauge, can you watch the temp go down when the thermostat opens? I watch mine from time to time and it works like clockwork. The temp will rise to about 195-200 then the t-stat opens and it drops to 180-185. If it just keeps climbing I would still suspect the thermostat. I have never had air pocket problems but I would think they would work themselves out eventually.

When I have to diagnose overheating problems I like to look in the radiator cap while the engine is running but still cool, and watch the coolant flow through the radiator. You should be able to see all the tubes flowing freely. The coolant level has to be a little low for this. If it is full to the cap you may not see the tubes. Good luck.

[Kev442]

Does your lower radiator hose have the spring in it? It sure sounds like something is causing cavitation in the water pump.

[Chops442]

The hose does have the spring, it's definitely not flattening. I'm going to swap in a new/better water pump just in case it is expanding with heat and getting loose on the shaft, and swap out the heater control valve for a bypass.

Has anyone used this?

http://summitracing.com/parts/BRA-1775/

[oldskid76]

Have you checked your temp sending unit and gauge just a tought

[73rocketship]

I had this same problem when i rebuilt my 455 and after many headacks it truned out to be the clutch fan . Seemed fine when it was cool but when it warmed up it started to slip. Once i bought a new high quialty clutch the temp on the motor ran at a stedy 190 degrees:)

[zodiacblue442]

Lots of good suggestions posted, the clutch fan is another good suggestion. That very well may be causing intermittent overheating as you describe.

In response to the Flow Kooler water pump, they are fantastic! That's what I run on the race car and also on my 442. Well worth the $$$ and they aren't that expensive, IMO. The impeller design really moves the water. I was going to suggest you try a Flow Kooler water pump if you were going to replace the pump, but you're one step ahead of me. :p

Good luck.

[Chops442]

Then that does it; I'm going to get one of those Flow Koolers ordered and throw it on there this weekend. It is defintiely not the gauge or unit. Before I had the intake bolt holes helicoiled where the thermostat housing bolts on the pressure was building up to the point where it blew the back of the housing gasket out just enough to bleed off the pressure.

It's not the fan clutch; flex fan with spacer.

[TripleP]

I think a key clue to the overheating is that it happens so quickly. If I understood right, it happens in less than two minutes.

I think it must be that the coolant isn't circulating, whether that's from a faulty waterpump, malfunctioning t-stat, air pocket, or a physical blockage someplace.

I'd start with the easiest thing first by trying to work out any air pockets. As mentioned earlier, you can unhook a heater hose and try to chase the air out that way.

Next try the t-stat. I once got three dud starters back to back to back. The lesson that taught me was that you can't immediately assume that a new part fixed the problem.

After that, I'd look at the waterpump. As someone else mentioned, the waterpump can be deceiving. The pulley could be turning but the impeller is seized and because of a broken shaft, it looks like it's working. I don't think this is the case in your situation but I've seen OEM and aftermarket serpentine belt systems where the belt has been run incorrectly causing the waterpump to run backwards and that leads to some very frustrating diagnostic sessions.

Lastly, you may have to do some "exploratory surgery." When the motor was apart for the cam, is there anyway a foreign booger of some kind could have found its way into the cooling system and is causing a physical blockage?

I find cooling system problems incredibly frustrating. In my opinion, it's one of the least complicated systems in any car so when a fix isn't immediate or obvious, it sucks my will to live.

All the best and let us know what the ultimate outcome is!

[Bill V.]

The problem is the new cam. The valves are not spending enough time on the seats to transfer away the heat. The intermittentness is caused by the lifters being right on the edge of being too tight. When you RPM it a little hard the lifters pump up and don't recover. You can prove this out rather easily by removing all the rockers and placing a standard flat washer down all the rocker studs first and then putting the rockers assembleys back on. Besides curing the overheat this should also wake up a lot of sleeping ponies. BUT, this is only a temp cure. There has to be a mismatch in the valve train geometry. More than likely push rod lenght too long. Try it, it's not a ten minute cure, but it's inexpensive. Bill V. Pnx. Az.

[Chops442]

I did have the motor borken down to the short block when I changed out the head gaskets, but I was very careful to keep it surgically clean, so that should not be the deal. The water pump felt locked in to the shaft when I had it off, but it is an old pump, and with all the heat issues, I am just going to throw a better one on there. I'll bet it is an air issue somewhere, so we'll roll with a new pump and pulling those heater hoses, and see where we get.

[73431Cutlass]

My 425 has always ran a bit hot, along with my 455. I have the lightest springs in the distributer but the heavy weights. I had my cam 2 degrees retarted. I put in a Flow Koller pump, high flow T-stat heavy duty fan clutch and a big aluminuim radiator. When I bumped the crank sprocket 4 degrees it turned the can 2 degrees and it runs a lot cooler. It went from running 210 to 220 to 180 to 195 in the spring or fall. I dont drive my car in the summer unless it is to a show. If you use a Flow Kooler go out and buy 2 thick felpro gaskets. You can use the thick one supplied and a felpro together. If not your impeller will grind the timing cover. I would lean to the cam timing on this one. Maybe the valve lift as a 2nd option, make sure your geometry is right.

Steve

[djb56]

The rule for cams is that you shouldn't go over 500 lift(olds) unless you have special heads that can take the extra lift and valve train. Valves wont close. When you ordered the cam from Mondello did you talk to Joe himself. The guys taking the order dont know everything. You didn't mention what kind of heads or the year that you are using.

[sledhead2]

when you had it apart did you have head pressure tested? to me it sounds like a cracked head pumping air into system or head gaskets. I know gaskets are new but what kind are they?

goto parts store and tell them you need test kit to see if there is exhaust fumes in coolant or take it to a shop and have them run the test.

Good luck

[442MUCH]

The rule for cams is that you shouldn't go over 500 lift(olds) unless you have special heads that can take the extra lift and valve train. Valves wont close. When you ordered the cam from Mondello did you talk to Joe himself. The guys taking the order dont know everything. You didn't mention what kind of heads or the year that you are using.

The lift on my cam is 528 and the heads are factory "C" with porting in the bowl area. I have not had any problems to speak of. When you say "special heads" are you talking about anything other than the "J" heads?

[djb56]

The c heads would be ok. Anything from 72 back that was used with the bigger stock cams will work. There are some heads that have a deeper valvespring pocket. Those are the ones you have to watch out for. With those heads anything over 500 lift could give you trouble. The valves wont close because there is to much lift.

[Chops442]

I didn't think about the lift; that's a good call. I know I am really pushing it @ 512/523 without adjustable roller rockers on J heads. I have a set of Crane rocker arm shims designed for this that I bought to use with the lunati bracket master cam years ago, but that cam @ 496/512 really worked fine without. Here recently, however, I do remember the exhaust valves looking awfully white when I had the heads off to swap the gaskets. I will crack the valve covers and rockers off and put those shims on when I install the Flow Kooler, and that HOPEFULLY should do it.....

Any of you had much luck with roller rocker set ups? I've had some on some chevy's but not an Olds of course. I think Mondello has an entry level set for $3-400?

[zodiacblue442]

That is alot of lift for a basically stock valvetrain setup. The Comp Cams adjustable roller rocker kit works well. Part number is 1442. This is what's installed in my race car's 455 and it's got a high lift cam. A friend of mine that I race with also has a high lift cam in his 455 and is using the Comp Cams kit as well. The engines run great!

[73431Cutlass]

If you go with adjustable rockers you need to do a few things to the heads. Depending on the stud size you may need to change them and have the holes retapped and you should have the rocker pad busses milled for the guide plate. If you use the Comp cams studs you might be ok with reusing the stock pushrods. They are short and the base is small so the rockers can go down more. On my conversion I used Chevy studs because I had 3/8 holes on my 425 A heads. My studs are longer than the Olds studs. I had them re tapped for 7/16 IIFC and had the pads milled the thickness of the guide plate. If you dont mill the pads evreything moves up a little. This keeps the geometry in sync and keeps the angle of the rocker to valve realatively consistant to stock. In 90% of applications you will need to get new pushrods, I used the ones supplied with the 1442 kit and my rockers ride good on the valve tips but are very noisy. I am in the process of re checking them with a push rod checker. I have a feeling from what I have read about I am anywhere from 1/2 to 3/4 inches to short. I hope this rambleing helps you out.
Steve

[Chops442]

In reality, I would like to get some better heads and do all that to them; I can't really justify putting a lot of cash into a set of J heads even if I've ported them up a bit. Hopefully all these things will get me running OK until I decide to throw some $ at some older castings or a set of Aluminum heads. The instructions for these Crane shims specifically say they're for this problem, so maybe I'll get lucky. I've literally had them in my toolbox since 1993.

[mdkingsley]

http://cgi.ebay.com/ebaymotors/Oldsmobile-C-Heads-455_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a2Q7 c39Q3a1Q7c72Q3a1171Q7c293Q3a1Q7c294Q3a50QQ_trksidZ p3286Q2ec0Q2em14QQhashZitem3ef6572f68QQitemZ270420 881256QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessor ies

[rotagyllaw]

I hope indeed you dont have a major problem, the thought that its intermittent... Im guessing you already checked with another known good gauge or sending unit, or temp gun? I know ive had my share of problems that appeared to be overheating and in actuallity werent. I'm going to compare this to the issues that the 350,260 v-8 and 262 v-6 olds diesels had...ok guys dont make fun of me just yet... I do still have one of those at home in an 82 ninety-eight... point is as they were known for head gasket issues, what i have done as a preventative measure to keep from developing an air pocket at the thermostat and toasting an engine if a problem does develop (besides buying one of the failsafe stats incase it sticks) is drill a very tiny hole in the thermostat and reinstall it, will let any air through and an insignificant amount of coolant to bother the thermostats opening calibration. the thermostat housing on my diesel , compared to my 77 cutlass is almost the same except the waterpump bypass portion on my diesel is cast in an open manner whereas my cutlass isolates the 2... maybe that was gm's way of already doing what i mentioned, hope this was a help to you... I know how sick i would be if anything of mine were to start overheating intermittently. Good luck, happy Oldsmobiling

[Hot-77]

is it actually boiling over? if the guage is pegging 240-260 like you say it should be shooting coolant throguh the overflow bigtime,,,if not the sending unit or guage itself could be bad giving a false reading...just a thought since nobody mentioned it yet,,,,on another note you say the pump is good by looks? you cant really tell with a naked eye if the impeller is worn as it "shaves" itself over time with the aid of the coolant friction...a very light loss of impeller surface can cut the pumps ability to move water drastically and it only takes a few minutes of having a "dry pocket" on initial startup near the sending unit to create a high reading and vapor lock the system....i'd seriously try a new waterpump before you get the cherry picker..good luck, Myles :cool:

[atdog]

I know this thread is old, but I'm curious about what happened...what finally solved the problem?

[hurst73]

Just a suggestion- Ditch the flex fan and go with an OEM Clutch fan or an electric. My brother had the same issue on a 78 CS with a Rocket 350. After a while, the flex no longer flexes as it has encountered metal fatigue. Also, be sure that you have a 4-core radiator that can dissipate the heat efficiently. The cracked head scenario also sounds legitimate. A simple leak down test on each cylinder can do this. Also, pull the ts housing off while leak down testing to see if compression air from the cylinders is being pushed into the water jacket. If bubbles appear in the coolant in the ts housing, look for a head gasket or cracked head.