85 Eldorado overheat conundrum!

[danjarrett1]

Have been bringing my 1985 Eldorado back to life for a few month now. The car only has 65k miles and has been garaged its whole life. When I first bought the car, it had been stored for about 6 years. The previous owner elected to pull it out of the garage and start it. It started with some coaxing but quickly overheated. I bought the car knowing full well the history with these engines. I flushed to cooling system repeatedly until it was convinced I had sufficient flow. Used the AC Delco pellets, etc. I did run a block test, confirmed hydrocarbons in my antifreeze, oil it clean as a whistle. I know.....pull the heads and replace the head gaskets!!!! But at the encouragement of another driveway mechanic. Friend, he suggested Bars Leak as a possibility. My instincts told me “that stuff never works”. In tried it, not sure about the outcome just yet.....but here’s what has surfaced: now that the OAT is in the low 70’s, the only way I can drive the car without the overflow reservoir being overrun is to leave the heat on all the time! I’m taking from this that by circulating the coolant through the heater core, I’m expanding ways to remove heat.....do I have insufficient radiator flow? Buy new radiator?

[The Tassie Devil(le)]

G'day Dan,

One of the problems with any material to stop a leak from any cooling system is that they could start to block up the internal passages if not used as per makers directions.

Years ago, way back in 1964, my first car developed a leak, so I did what I was told, and stuck in a can of radiator Stop Leak.   NOTE, Not Bars Leak.   All was good for a while, till one day, whilst passing an expensive car, the engine decided that it was too hot, and threw a leg out of bed (Con Rod), which left me stranded.   Tow home, fit another engine, go for another drive, and this time it overheated and spun some Con Rod bearings.

Upon disassembly, it was found that the radiator was so blocked up, solely because of the Stop Leak, that the coolant flow was just not flowing.   There were so many holes in the radiator that as each one got sealed, the internal sealing properties of the Stop Leak eventually "killed it".

By circulating the coolant through the heater core, brings me to the conclusion that the Radiator is not working, and the Heater Core is an extra radiator.

Before simply tossing the radiator away, have it cleaned out properly, that is by having the top and bottom (Or end) tanks removed and each core tube rodded out.   Flushing won't be enough.

Bruce.    

[danjarrett1]

It is getting more and more difficult to find someone to rod out the original radiator, we have become a “remove and replace” society. My prose fence would be to have it cleaned and reinstalled but I can buy a new one for $250 delivered......

[The Tassie Devil(le)]

To test the capacity of the radiator, I would be removing it, and with it laying on its' side, or at an angle with one fitting blocked, fill the radiator with water, and then measure how much comes out.   Or, do it the other way, and with a jug, measure how much water it takes to fill it.

This will give you an insight into just how much it could be blocked.

Bruce.

[James Landi]

Having owned four Cadillacs with 4100's, I have  experiential knowledge of your problem--- as stated already--- BAR's is a disaster for these engines.  You may have a load of accumulation at the base of your engine's  two water jackets.  May be a good idea to pull the drain plugs on both sides  (have a coat hanger wire ready and a bucket--)     The point mentioned above about the original radiator is right on target.  If you can get it professionally cleaned, go for it.  THe aluminum replacements are marginal (based on experience).  Do you have the correct thermostat installed?  The housing on the 4100 will seemingly accept a wide variety, but some of them will not permit the valve to open all the way, thus blocking the flow.   Try running your engine without the radiator cap on... and look to see if you have a stream of bubbles.... if so, you still have a compression leak somewhere, and that's pushing out the coolant.  Also, install an electric temperature gauge... cheap insurance.  One of my 4 4100's ran a full 317,000 miles for me-- that's one out of four--- and that engine ran for many miles with a nearly entirely plugged catalytic converter and a stuck heat riser... so don't give up!    Hope this helps,  James

[danjarrett1]

Thanks James, all good info. I have the factory manual on the car put cannot locate the factory drain plugs as described. I am increasingly convinced that I have a flow problem.

[James Landi]

I reread your first post--- yes--- when several of my 4100's began to show 235 degrees on my aftermarket gauge, I'd run the heater, and the engine would cool down. Of course, this would occur when I had the a/c on and the weather was HOT!  So flow may be the problem, but first, I'd check the radiator for build up and the lack of effective cooling. This is an insidious problem as calsification is hard to see since you only can view the very top end of the cooling tubes through the radiator fill.   Can you get this radiator DESCALED.  Is the original cooling system air shroud still in place?  When the car is not under load, does it over heat? Your heat raiser valve may be stuck closed-- it's vacuum actuated, and I believe you can move the valve flap manually-- check that out.  Do you have a reliable temperature gauge? how hot does the coolant get when the car begins to heat up to idle temp.  How about that thermostat?   So flow might be the issue, especially if the thermostat is bad or it's the wrong one and can't open, or more likely, the radiator is partially blocked and is impeding the flow and also not effectively cooling the engine.     And yes, there may not be drains in the base of the water jackets...  When we converted my 85 4100 convertible to an Olds engine, we had the 4100 with the heads off, lying on its side, and accumulated gunk oozed out...     Keep the narrative going if you feel I'm helpful.   James

[danjarrett1]

I installed the correct thermostat, 195 degree. Replaced all lines related to cooling. I do like the idea of having a separate analog gauge for monitoring coolant test, need to find the coolant temp probe under the AC compressor and piggyback a connection to a real gauge. That’s old info in the heat riser flap, I will confirm open....when I first got the car, the res ovoid tank had two inches of dex-mud” residual in in the bottom of the tank.....flushed the radiator 15 times...but may still,have blocked passages and such

[James Landi]

DId you truly have DEX in there--- that coolant is not compatible with green coolant, and if true, there could  still be gunk in the radiator-- I don't know--- just guessing, but there  is certainly web info on what happens if you mix.  Radiator de scale is is a technical process that involves some serious and potentially dangerous chemical reactions, and is truly and old "art form,"   for technicians who are now in their 70's.   Back in the late nineties, I could still purchase original equipment Cadillac radiators... perhaps some original equipment is available... the aluminum replacement might be the way to go, but as I mentioned, the aftermarket ones really vary in price and performance.  Might wish to start a new thread assigning that as a question for members.      I think you're on the right track, but check that heat riser exhaust valve for operation.    James

[danjarrett1]

I have located aftermarket radiators, 2 row, aluminum I expect. There seems to be a lot of strong feelings about dexcool. I have used dexcool for a number of years without any issues at all. Everyone strongly suggest on this forum that dexcool is junk and that yellow Prestone is a better solution for this series car. I realize that dexcool,and Prestone are chemically different from each other, just can’t imagine why GM dexcool  is not a good choice for the 85

[hornetball]

I do like the idea of having a separate analog gauge for monitoring coolant test, need to find the coolant temp probe under the AC compressor and piggyback a connection to a real gauge.

These devices are resistor bridges.  If you "piggyback" (which I read as connecting both in parallel to the same sensor), then you will ruin the reading for both.  Each measurement device needs its own sensor.

[danjarrett1]

Good point, will have to find another resource for temp. I have seems an insert that fits into the radiator hose that can accommodate a separate temp probe. Has anyone had any luck with this configuration?

[hornetball]

Good point, will have to find another resource for temp. I have seems an insert that fits into the radiator hose that can accommodate a separate temp probe. Has anyone had any luck with this configuration?

That type will work after the thermostat opens (assuming you have good flow through the radiator -- which seems to be questionable here).  Best location is in a waterjacket on the block/head side of the thermostat to warn you if something is going awry.

[James Landi]

On one of my 4100's that I remember well enough to describe, I took out what I think was the "idiot light" probe on the top front, just to the left of the A/c compressor, and substituted the electric gauge probe.  If memory serves, it was a quick and easy installation.   The more challenging part is finding an ignition switched circuit for the gauge, and figuring out just where to hang the gauge. I took out the ash tray and installed an engine oil pressure gauge, and I also installed a gauge that "teed off" of the air ride compressor.  Gave me some distractions prior to smart phone tech.  James

PS: Dex is fine if it's not mix and there are no leaks.   

[79 Eldorado]

A gauge in the car is ideal for noticing something changing and quantifying the high temp but you can also get a relatively cheap infrared pyrometer to spot check different areas under hood and that might be very useful now because you know something is wrong. You can probe different areas. For example an area before and after the thermostat. It may be difficult but you you could even try to probe different sections of the radiator (at least the entrance and exit tank). The thermostat sticking was my first guess but it sounds like you covered that. There is always a chance that a new part was bad though and not knowing the 4100 thermostat housing configuration well I need to ask if you are sure the thermostat was placed in the correct orientation.

As I recall Harrison radiator had already started switching some radiators to Aluminum starting in 1984. By the time the conversion started to occur the metal gauge on things like the air center were being reduced. I bought an original replacement for my 1979 Toronado around 1990 and it lasted about 1 year in WNY before the lower fins basically had no integrity left; disintegrating.At that time the Modine replacement cores wer much heavier gauge. It wasn't obvious until I pulled it and looked. At the time it was frustrating because I had rebuilt and changed everything except the heater core. The "everything" included the radiator...but 1 year was enough in WNY salt. I actually started to have the issue even before 1 year but it took me a couple of months to question the relatively "new" radiator.

Aluminum radiators can be fine but you never know what alloy the manufacturer is using. Our original heater cores are also Cu/Brass so it means the Aluminum radiator will be living with a source of Cu in the system. That can work as well but in general Aluminum really doesn't do well in the presence of Cu. That may be important to mention especially if the stop leak has Cu in it. Does anyone know if you can still get a Cu/Brass re-core? There was a place in Michigan(?) reproducing some GM radiators. I recall seeing the website a few years ago but not certain I could still find it. I personally like the original look. If I replaced the radiator for an Aluminum one I would at least save the original in the event it was possible to get a re-core in the future. At least "back in the day" I was told sometimes the original oil coolers were better than the ones in a new replacement so a re-core could be an advantage of a completely new core. Back then it was easy to get a re-core but now...I guess it's not. BTW impossible to find a Cu/Br heater core for these cars now; only Aluminum are available.

The big issue with dexcool is it can only protect completely when the system is completely full. I mean dexcool must stay in contact with all of the metal. The old school coolants basically left a thin film layer on everything it touched so even if the coolant got low there was some protection. If dexcool gets low you have no protection of the areas not in direct contact.

Scott

[DHeins]

I used K-Seal (super fine zinc). Solved the problem of losing a little bit of antifreeze every year. Have been using for the last 6 year and no more leaks. The tablets suck. Also got rid of the old brass radiator and put in aluminum. No worth the trouble to rod it as it was so clogged up.

Here is the K-Seal web site FAQ's https://www.kseal.com/faqs#index4
that shows it's safe for aluminum
Here is the SDS....mostly Zinc with a very little trace of copper and PH of 5.9 (neutral)
https://www.kseal.com/wp-content/uploads/2018/11/K-Seal-US.pdf