87wagon

I have a 87 caprice wagon, with a olds 307. The engine gets hot while driving on the highway. It will get well over 220 and boil over into the overflow. The car is 100% stock. So far I replaced all the hoses (with lower rad hose spring), the rad has been rebuilt, high flow t-stat, added water wetter, rebuilt carb, new heatear core, new intake manifold gasket, and complete tune up. When I drive around town the temp is fine ( with ac on). The OD works fine. My next move is a high flow water pump. I also changed the temp sending unit. Any suggestions would greatly help. 50k original miles. I also played around with different t-stat temps.

J-(Chicago)

There isn't much to the cooling system.

-Radiator inadequate?
-Thermostat stuck closed?
-no fan shroud or incorrect fan shroud?
-Bad fan clutch?
-bad water pump?
-air pocket in the system?
-Heater control valve stuck?

MDchanic

Classic symptom of an inadequate radiator, but all of that other stuff should be checked as well.

- Eric

Rickman48

If a tank of premium makes it go away, your initial timing is too advanced!
Could also be a lean condition - did ya check all the vacuum lines?
Is your gas mileage the same as it's always been?

Lady72nRob71

A good 307 does fine stock in the hottest weather with the Ac on.
A high-flow pump would only be a bandaid. Are all the rubber seals in place that direct air from the grille through the radiator? The air dam looking thing at the bottom in front? Are the front wheelwell rubber flaps over the control arms there?
Timing set to stock? Is a clear 3 row radiator in place?

Sugar Bear

X2 on what MDchanic stated. Had this on a 90 Caprice 307 Olds motor in a super clean low mileage station wagon that ran hot on the highway. The solution was a new radiator.

Look for air flow restrictions leaves etc., between the A/C condenser and radiator, confirm that the air tubes in the radiator are not rotted or clogged and that the air dam under the radiator support is intact before changing the radiator. If you replace the radiator with a new one you will probably notice that the old one will be a lot heavier due to clogged internal tubes.

87wagon

I had the radiator taken apart and rodded out and it did not change the temp.

I think that all the air dams are in place. Does any one have any pictures of what should be there as far as air dams and deflectors?

All the vacuum lines are good.

Gas mileage has been the same avg 12/16

How do i check the heater control valve?

What temp should the car run at in 100 deg weather?

Thanks for all your help, I am surprised that I am getting so many replies.

Lady72nRob71

Certainly check the timing.
Radiator (if stock type) shoul dbe 3 row, not two. Make sure the correct one is in there.
Heater valve should not cause an overheat condition.
I will try to remember to look int he service manual for the deflector setup. If someone can post pics of their car, it would be great.
Anything over 215 would concern me, however the factory temp light does not come on until something like 250*!

MDchanic

With a 305? That seems low to me.

No. As Rob said, it has nothing to do with this.

It should be the temperature of your thermostat.
195° thermostat = 195° temperature, more or less
(With possible thermostat and fuel gauge inaccuracies, 200-205° is within reason).

- Eric

87wagon

I checked the timing, it is set at 20 deg. That is what the sticker on the shroud says.

I am leaning torwards to water pump impellers being worn out or corroded.

Any other things that could cause this?

All the shrouds and defelectors seem to be in place. However pics would be nice to verify.

oldcutlass

The only other thing that would cause it if all else checks good would be a blown head gasket. Look for bubbles in your radiator, and perform a compression check.

rustyroger

I've come across a few cases of worn impellers, older UK spec Nissans (still Datsuns then) were the the main culprits but it can affect any car.
But the cars concerned had overheating issues at any speed including idling.

My guess is the radiator, rodding it out might not shift all the limescale. As has been said check all the shrouds and air dams are in place.
A 195 thermostat should keep the engine around 200 degrees on the highway.

Remember the stock cooling system in good shape worked fine for all the 307 powered cars that left the factory, adding heavy duty cooling system parts won't help until you find and fix the cause of your problem.

Roger.

ThePackRat

I had a 307 Toro that had similar issues.

Several things were replaced & they didn't help.

What ultimately brought highway speed temps back down to normal levels was :

1 - A new radiator.

2 - A new catalytic converter.

oldcutlass

The catalytic converter makes sense as this has not been mentioned previously. Most of us have pre-emission rigs and don't really think about the converter.

DeltaDevil88

I had overheating problems last summer in the DFW a new AC Delco 3 row radiator was the cure.....but I also had water pump replaced with a new one and a new clutch, running a 180 tstat

Pretty much a whole new cooling system in my old 307.

Lady72nRob71

Cat converter can do this? Interesting - never heard of it.... Perhaps when its restricted?

87wagon

My radiator was rodded out last summer, does that not help sometimes? I am pretty sure it was dipped in a hot tank before it was taken apart and rodded.

Can a muffler shop check my cat for me?

The car runs at about 220 in town with a 195 T stat.

Also, the car seems like it lacks power. The lack of power really shows going up hills. Im not sure how much power the big heavy station wagon should have. Its only like 140 HP or so.

Lady72nRob71

The 307 is pretty underpowered but in 3rd gear, hills should not be too big an issue.
220 in town is a bit hot, too.
Can you tell if the radiator is 2 or 3 rows wide? Take the cap off cold and look inside.
A previous owner might have put a cheap 2 row in in place os the required 3 row.
If it is 3 rows, and it was rodded out, it should be fine!
Muffler shop should be able to check the cat.
Do you have any check engine light?
Have you pulled a couple spark plugs? If they are glossy white, then it is running too lean, which can cause low power and overheating.

rustyroger

Only sometimes, I would never rod a radiator, instead I would have it re-cored.
However if keeping a car completely original is important I can see the case for it.

Roger.

Jamesbo

Yes, Most muffler shops can check the cad for you. Sounds like that may be the problem.

Rickman48

YOU can check it, too!
See if it's glowing hot after about a 20 mile ride!
Is your performance and mileage down??

oldcutlass

Generally you will see a reduction in power, and you can heat the reduced exhaust flow when a converter becomes constipated. What we used to do is put a temporary (I use this term loosely) bypass pipe in place and see if the problem is corrected.

ThePackRat

307's can be be tough to gauge sometimes power wise (& what's normal) ... as they aren't exactly powerhouses & generally come saddled with lazy gears out back that add to the problem.

Having an actual temp gauge like you do ... to tell you that's it running warmer certainly helps.

In my own real world experiences .....

220 is too warm if you aren't doing anything to warrant higher temps ... such as towing - going up a long steep hill - sitting in the sun with the a/c on idling for hours on end etc etc etc.

Most traditional Olds V8's of any size that I've ever dealt with start giving up some power after 200 degrees.

At 210+ ... it starts to become pretty obvious.

This issue is compounded on a 307... as there isn't all that much power there to begin with. The more power you start with ... the more "reserve" that's there so to speak.

My 307 Toro would climb to 230-240 before I got things in check with it.

The power levels at those temps were nothing short of suicide.

Sluggish is not the word ... I just can't stress enough how dangerously S-L-0-W it became at those temps.

I would imagine the converter played a part in this.

Funny thing was ... the engine ran fine otherwise.

It idled so smooth ... your could balance a nickel on the air cleaner

I don't even think it ever boiled over into the overflow.

The temps never acted up at idle ... only at a brisk cruise & highway speeds.

I also had a 307 Cutlass with similar issues that ended up with a new converter & radiator as well ... tho it wasn't quite as bad.

Even if a converter doesn't cure your issue 100% ... I think you would still see an improvement in temps, not to mention performance & gas mileage. The converter's from that era were pretty restrictive from day one. And considering yours would be @ 25 years old at this point (if original) ..... I feel it be money well spent.

I don't think you have a fan clutch issue as that should be more of a problem at idle & low speeds.

If it were in fact bad & all else was fine ... things should be cooling down once you get moving & are getting good airflow over the radiator.

Only other thing I can think of is making sure the EGR is functioning properly & nothing is plugged up.

When that acts up it can cause some pinging ... so I'd imagine it could have some effect on engine temps as well.

87wagon

I am going to get the converter checked tomorrow. I might get a new less restrictive exhaust system installed. However, I am trying to figure out what the 3rd muffler looking thing is in the rear of the car by the spare tire hump is. Is that thing needed?

The car does ping with cheap gas. It will idle and drive in stop and go traffic with no rise in temp. It runs cooler! When I start to drive is when the temp starts to rise. The cat looks original I am allmost 100% it is original.

The radiator is the original metal tank 3 row from the factory. The radiator guy said that it was rodded out before, leading me to believe that this problem has been going on before. When I bought the car it only had 35k miles.

Would dual's from the cat back help performance or am I beating a dead horse?

Thanks for all your help guys and gals.

ThePackRat

An improved exhaust would certainly help.

I guess they could split it with a Y-pipe right after the cat like they did on the VIN 9 G-Bodies ... or perhaps you could do a single in/dual out muffler.

Just keep your expectations reasonable & don't expect to feel 350 power out of a 307 without better gears & a torque converter.

Size wise ... this is one time where bigger isn't always better.

If you were working with a modified and/or bigger engine things would be different, but in this case .....

I would go with no more than 2.25 inch pipes.

Anything larger would probably cost some power vs gaining any for you.

The piece near the spare hump is most likely a resonator. That is mainly for making things a bit quieter vs without.

Overkill IMHO in stock or near stock applications.

As long as your don't go radical with your choice of a muffler (too loud) I would not worry about installing any resonator(s) back on.

ThePackRat

PS -

Even if you don't end up going with a dual tailpipe setup .....

A new muffler might not be a bad idea.
(in addition to the CC of course)

Debris from the converter could have made its way back into the muffler.

Rickman48

'3rd muffler thing' is a resonator - probably not needed with a convertor.
A true dual set-up, with dual cats and a 'H' pipe would do a lot of good!
May have to re-jet the carb for optimal gains, but should be able to feel the difference.
Step up to 2 1/2" if you're thinking of a 350 down the road, if not 2" will suffice.
That's if you need cats where you are!

87wagon

What do you guys think about a high flow cat? I need a cat where I live.

ThePackRat

A standard replacement these days is still much better than the original .....

But if it were me ... I'd still go with a high flow vs a standard.

87wagon

I just got the exhaust system checked. They said that it is fine. No restrictions.

I guess the water pump is the problem.

Any suggestions?

MDchanic

Yeah, and it will annoy you:

Change the radiator anyway.

Sorry.

- Eric

DeltaDevil88

R-a-d-i-a-t-o-r

ThePackRat

I still can't help but feel this will end up being a combination of both the rad & the cat.

Hopefully they knew what they were doing where you took it.

Throw a new rad in & let us know what happens.

87wagon

I changed the fan clutch as a last resort. It was only $30.00. It seems to be running cooler and not climbing past the t stat temp too much. However, it is pretty cool today here in Phoenix today 65 or so. One thing I noticed was it seems to heat up a little at stop lights then cool off when driving. The old clutch felt like the new one, same tension when spinning and would loosen up after a few turns. Is that normal for a bad one to act like that. The old one looked like it was replaced in the past, it was clean and new looking.

I am getting a Magnaflow muffler installed today to let it breathe better.

I will keep everyone posted on how the temp gets. I will try to find a hill here in Phoenix to climb!!! I will be upset if it was the fan clutch and have been chasing a ghost for 2 summers.

87wagon

One more thing. The guy at the muffler shop checked the exhaust with a heat gun and said that there was very little difference in temp in the exhaust system. Before and after the cat and muffler. Also, the pressure coming out the tail pipe seemed to be normal for that engine. He said that my cat was a less restrictive one than other types (like the pancake style) and a new one would be a waste of money. So he talked me into a new less restrictive Magnaflow muffler with a unbaffled design.

MDchanic

These are two completely opposite problems.

We need to know which one you have in order to give the best advice.

- Eric

87wagon

That happened right after I changed the fan clutch. I have not driven it enough to really tell what is happening. That was one thing that I noticed. It did not rise very much, the needle moved just a little. I also just put a 180 stat in from a 195. How many degrees should it rise above 180 to be a good operating temp? Is a slight rise in temp normal at stop lights? Maybe the rise in temp at stop lights happened before and I did not notice it. Afterall, I was watching the temp gauge like a hawk.

87wagon

I just read you post MDchanic. The temp should be 5-10 deg hotter that t stat. Is it the same in 100 plus weather. It gets really hot here in the desert.

oldcutlass

A 180 deg stat in lower ambient temps will read approx 10 deg higher. At 1oo deg temps it can go 20 degrees higher. In traffic it would not be unheard of to go to 210-220, but quickly recover once the car starts moving.

87wagon

The new Magnaflow muffler really works great. It has a very noticeable improvement in power. I took it for a drive yesterday and the temp was stable. However the temp outside was cool. I will keep everyone updated.