Bad Radiator or blown head gasket?

2000 Chrysler 300M with 142K miles. Was a very reliable car until recently.

Problem began with boiling coolant in the reservoir tank. Then began to lose coolant at a high rate. I tried stop leak products and replaced the coolant frequently for a couple months. Some of it kind of worked, but the problem always returned. The car drives fine for about 10 highway miles then begins to steam out from under the hood on the passenger side. It gets about half way up the temp gague, but does not really overheat. I usually stop when it steams out, let it cool, replace the antifreeze, then do it all over again. I’ve also tried a bunch of other things too, e.g., radiator flush. None of it worked. I know I probably made some mistakes here, so please don’t tell me about them. I just need to know what to do now. The mechanic wants $700 to replace the radiator. Says the system does not have pressure so there’s no real way to determine if there are leaks in the engine. But he does know that the radiator is no good. I’m okay dropping the $700 on the radiator, but don’t want to do it just to find out ten minutes later that I have a blown head gasket, which I would opt not to fix. I have read the tell tale signs of a blown head gasket, such as coolant in the oil, but there is none. My exhaust is white, but it’s 5 degrees outside and it doesn’t look whiter than anyone else’s. I have seen some coolant on the ground at times. Help!

Have you tried looking for a fluid leak? If it’s on the drive, you should be able to look down from the top, over the drip and find where it’s coming from. If the radiator is the source, replace it the hoses and the thermostat.

is the car boiling the coolant out?had a similar problem but only ran hot under a heavy load.the problem was grout had built up in the passage above the thermostat which would be drivers side head,all the way forward. you can either remove the head, or what would you was removed the thermostat and put air pressure to has been over 9 months since we did the repair and I still talk to the person with no problems as of yet. The answer was given to me from an actual Chrysler technician. Hope this helps

You can buy a radiator yourself for about $100, it is not a very difficult job.

@oldtimer_11 You have to consider that the OP may not own a wrench or have ever twisted one. Since he’s already confessed that he would not mind spending $700 for a repair he could do himself for $100, I’m going to guess he is mechanically declined.

I’d like to know exactly what tests the mechanic has done.
Did he do a pressure leakdown test (he does not need to pressurize the cooling system to do this)? A hydrocarbon (lab) test on the coolant?
Did he do a pressure test?
Map the radiator?
Check for signs of corrosion damage to the spark plugs that might indicate coolant?
Did he test the thermostat?
The radiator cap (after all, he did say the system won’t pressurize)?
HOW does he know the radiator is no good? Is it obviously leaking? Did he “map” it? Did he do a flow test?

It’s unfair to make assumptions about the mechanic without knowing what he’s done, but if he hasn’t at least done some real diagnosis I’d go elsewhere. There’s entirely too much “shotgun maintenance” going on these days.

I would request of the OP that he look at his copy of the shop order and tell us what eth mechanic has actually tested. Or post a photo of the shop order. If the mechanic has NOT looked at the car yet and is stating definitively that the car needs a radiator, I’d go elsewhere.

If the OP has a few minutes he should go to a car parts store, buy a new radiator cap, put it in his or her pocket, go home, and the next time they go out to the car and the car is stone cold, not run in 8 hours or so, open the hood and replace the old cap with the new one. Then make sure the overflow tank is about half full, and drive like usual and see if the problem is gone.

MG MechAnik I was only pointing out the possibility. I had no tools at all when I did my first car repair at 16 on a 47 Fraser. My stepfather told me "You blew the head gasket, You fix the head gasket."My stepfather had no tool either and I only had $15 and the gasket set and a small bottle of Bullseye shellac cost $13+. I walked to the library for a Motors repair manual and to the parts store. Then I borrowed wrenches and screwdrivers from a neighbor and when I had it buttoned back up he called a friend who had a torque wrench to come over with it so I could finish the job.

You either want to learn or you don’t. It seems to me people don’t want to do things for themselves anymore. I know people who complain about not having enough money, but they pay other people to mow their lawns and plow their driveways.

No one has enough money but all the national chain restaurants are full every night.

My wife dropped and broke one of her glass pie plates and went to a local department store and asked the clerk in the houseware department where the pie plates were. The reply was “What’s a pie plate ?”

There are a lot of very intelligent people who have absolutely zero mechanical aptitude and even less interest. And that’s okay by me. I’m sure I could never do what some of them do. I was always great with math, and physics simply consumed me (still does), but when it comes to finances I’m a total klutz. And when it comes to politics I’m a stumblebum.

Many also have medical limitations that force them to pay others to do many things. And there’s another hidden reason why many are afraid to try. If one lives in a rural area and it’s one’s only vehicle, it takes courage to start a repair. If you need a part, or make a mistake, you’re stuck. No way to get to a parts store, no ride to work in the morning. That has on occasion caused me personally to have the work done. In 2013 (or maybe it was earlier) I wanted to change my struts, but I knew that if I got the car on the stands and my back went out I’d be screwed.

That actually happened to me some years earlier. I was going to put new front pads on my old pickup, but after I got the front ends on stands and the wheels off my back gave out. I had to get a neighbor to put my wheels back on and take the truck off the stands. I ended up getting an epidural and spending a week laid up, followed by three weeks or so in pain. That incident has caused me to reconsider my limitations.

I have had a very bad back for 58 years due to an accident moving a refrigerator ( They used to be much heavier then. ) I wouldn’t let them operate then and the worst it has ever done to me is keep me in bed for three days at a time. When mine goes out, it doesn’t stop me from getting down and working on a car. I just can’t get up again. I may have to lie on my back for a few hours with my knees drawn up before I attempt it. I just have my wife bring me a book and a cup of coffee.

“The mechanic wants $700 to replace the radiator. Says the system does not have pressure so there’s no real way to determine if there are leaks in the engine.”

Based on that, I’m going to make a few . . . possibly incorrect . . . assumptions

He’s intending to install either a factory radiator, or a high quality aftermarket part, such as Behr or Valeo. And of course, he’s going to mark up the part, which is the nature of the business

The radiator is visibly leaking. Perhaps it’s so obvious, that no pressure test is even needed to verify the bad radiator

When the mechanic pressurized the cooling system with his pressure tester, he saw coolant leaking from the radiator. And that may have been the only leak he saw at that point

he knows the radiator is the starting point. Meaning, replace the radiator, refill coolant and perform another pressure test. He also knows when doing the second pressure test, another leak may become evident, which wasn’t possible to spot with the bad radiator.

The rate at which this car uses coolant makes me think the radiator may either not be the only problem, or maybe it’s actually the symptom of something greater, not the cause

I’ll go a little off topic . .

Perhaps after replacing the radiator, it would be a good idea to perform a block test

Those of you that insist on calling it something else, or don’t know what I’m talking about, that’s fine. I’ve always called it a block test, and so have all the mechanics I’ve ever known. When using the term, nobody in the physical world . . . I’m not talking cyberspace . . . has ever corrected me or said my terminology is outdated. And many of them have used the terminology themselves.

What else are you going to call it?

It is what it is

Have you considered calling around to a few places and pricing a new radiator rather than sticking with one estimate?

A garden variety radiator with a lifetime guarantee from a local parts house can probably be had and installed for far less than 700 bucks.
Rough guess is a couple hundred for a radiator even with markup and a hundred or so for labor.

My feeling is replace the radiator and the pressure cap (new thermostat is not a bad idea either) and go from there.

Several applications of stop leak products have probably clogged the radiator, and if it was not defective before, it is now or at least has to be cleaned. I believe that it’s time for the OP to have the problem properly diagnosed by a mechanic who can actually see what’s going on, any diagnosis from any of us not actually seeing it or testing it is just going to end up costing more $$. And future driving while the problem exists risks bigger problems, more $$. Hey OP . . . time to get to a mechanic who can properly diagnose this, it’s not rocket science, but it will become an expensive problem if you don’t fix it properly. Good luck! Rocketman

There are tests that can be done to check for head gasket problems that will still work even if the radiator is kaput. Like cylinder leak down tests. I think in your case though, since you see no other signs of a bad head gasket, and as far as I know head gaskets are not a known issue on this model, and you’ve never overheated the engine from what I can tell, me, I’d be inclined to replace the radiator first, before assuming there’s a head gasket problem. It’s quite likely that will fix the problem.

" I usually stop when it steams out" and this I believe you have done Repeatedly? One or Both of your Head Gaskets is TOAST. It could have been an 18 dollar thermostat issue…or a rad problem, but you are long past this point. If the Rad is leaking without collision damage…its leaking because it was over pressurized by the blown Head Gasket. With 142K on the clock…you already used up your Disposable American Vehicle of this vintage. Fix this and watch the trans die next. Vehicle is Donezo. Sorry.


I’m not saying the OP’s problem isn’t a head gasket problem, but a radiator can leak for other reasons. If the coolant overheats due to a faulty radiator fan or coolant temp switch that can over-pressure the coolant and spring a leak in the radiator for example. And radiators can leak simply b/c of age caused corrosion.