Sorry if this question has been asked already. From my research, I couldn't find anything that's exactly my situation so I just thought I'd ask...

Was driving on the freeway and heard some knocking sound on the car... Pulled off the next exit and immediately shut off the car. That was maybe half a mile? Had the car immediately towed to the dealer.

Dealer replaced radiator, hoses, thermostat, gasket and coolant reservoir tank. Dealer said that the coolant temp got up to 270F. Is this bad? Does this automatically mean that the head gasket is blown? I don't see any milky substance in the oil. Dealer said they did a coolant pressure test and it held for about 15 minutes. During the test drive after parts were replaced, temps got up to 217F.

Radiator fans are seized and the CEL is on for a knock sensor. So I'm going to be replacing those. But I was just wondering if I should be even doing those if you guys think the head gasket is blown and my engine is done.

Any help or advice would be appreciated. Thank you.

 

If the cooling system held pressure the head gasket is probably intact between the water jacket and cylinders. A failure there would also give you white exhaust smoke. A failure between cylinders would give you a misfire and probably generate a misfire code. A failure between an oil passage and cylinder would usually give black or blue exhaust when cold before the cats heat up. A failure between oil passage and cooling system would give milky oil or oily coolant. The dealer should be able to do a compression test and a couple others and tell you. I bet you're ok.

 

Thank you for your reply!

Dealer didn't want to make a conclusion whether the head gasket is ok or not. Their next step is to have the radiator fans and the knock sensors replaced and see if that clears the CEL.

So you don't think 270F coolant temp is high enough to cause damages?

 

It could be the faulty sensor along with the bad fans that caused the overheating. I've had cars overheat pretty badly without damage. The only way to know is to go through the diagnosis. If you heard knocking there could be another issue or it could be the heat caused the knocking and ruined the sensor. Was there knocking on the test drive?

 

Thanks for the reply.

There is no more knocking now. Only issues now are the fans not turning on and the CEL for the knock sensor.

Will fix those 2. Just not sure if I'm wasting time and money if the head gasket is blown =(

 

Pretty good chance the head gaskets are fine. Even if one is not it's not the end of the world. Take the head off and replace.

 

I once was in the same boat, and you have to understand my dad is very logical, not one to coddle. So he said you should be fine. Cars are not that delicate. There has to be some window in which a driver can respond to an overheating situation (this was with my Volvo 264GLE). Then he said if I am wrong you're f'd and need a new car. Point being we can only worry so much, right? As long as you shut her down as fast as you practically could, you did the right thing and really if we were betting people the engine is fine.

Was he right? No he was not, both my head gaskets were blown and I had to get a new (from a salvage yard) engine. But that was a French engine, not a Japanese one.

 

I am very curious, how does the dealer knows that the coolant temp reach 270F? I think they are BS-ing you. I do not think our LS has some sort of monitoring system that log the temperature and you can download the data later.

I dunno about LS specifically but I just got back from vacation in CO. As comparison, IIRC my Land Cruiser with similar v8 as the LS reached ~215F while climbing up the mountains with ~1000 lbs on board. I have Scangauge mounted permanently so I can monitor the exact water temperature and other things. So... 217F after the parts were replaced, maybe there are air pockets when they drain the coolant. And again, how did they come up with exactly 217F? Do they have a scanner that were hooked up all the time during test drive?

If the coolant pressure test held, then I think you are ok. You can do engine compression test if you like.

 

Most radiator caps will hold pressure in a radiator until the coolant temp reaches around 250 degrees. If there was evidence of coolant on the top of the engine, around the radiator cap, that would denote the temp (internal pressure) reached above 250F, overcoming the spring pressure on the cap and perhaps reaching near 270F.


Just a thought....

 

@BCT , They said the ECU logged it. I don't know if it really reached that actual temp but they said it got so hot that it melted the reservoir. That's why they had to replace the radiator cooling fan shroud. But they could be BS'ing me like you said... I know they have systems that can read OBD2 real time data so maybe that's ow they saw the 217F during the test drive.

I looked into a scan gauge actually but didn't want to spend $160. So I just bought an OBD2 WiFi reader that can be connected to your phone for $20 then the app will cost $10 to monitor all real time info. I'll be monitoring coolant temps...

 

If you don't detect a sweet smell from the exhaust and/or don't see white smoke then you're HG is probably ok. That will be something to keep an eye on though...no one can really say with certainty.

However the REAL question is WHY did your car overheat? Did the thermostat stick closed? Did your water pump go out? Is there a blockage? That's the question you need to be answering. I realize you say the fins were stuck but this car uses electric fans and they only do any good while stopped...while driving there is more than enough airflow to cool the radiator so even if the fan/fins are broke while moving you wouldn't overheat...only while sitting still...unless they are totally clogged that is.

You shouldn't need an obdII monitor, your temp gauge should suffice, if not, fix that too.

 

they're not lieing....freeze frame data would capture engine conditions when a code is set. Easy to retrieve that via Techstream or whatever tool the dealer uses.

 

I still bet the engine is fine, from everything we know is ok. Dealers are too quick to throw parts at symptoms. For example, my indie said you don't need to assume you need a new t stat at the timing belt job nor a serpentine. We would tell you if you needed these, we don't just waste your money....a colleague just stopped by was told he needs a new CAT and dealer said $1200 (he has a GM SUV like my wife's). I said I'll bring my reader in tomorrow and we'll read it and reset (dealer left it). My wife's ABS light just turned on again does it ever end lol life is too da** funny and too short to worry. My reader can read ABS and it's a $7 part on amazon, brake pedal position sensor.

 

My v8 in my Tundra was ruined when the radiator failed. The engine ran pretty much dry and my first indication was power loss followed immediately by my shutting it off. Too late tho. Zero compression on most cylinders. Turned over fast when cranking like the plugs were removed.

My guess is you are fine but if you are concerned about wasting money on it you will need to get a compression test. If ok you should be fine.

 

Thanks so much for your responses guys!!! I sincerely appreciate the advice and reassurance. I really hope my head gaskets are OK. I looked at engine swaps and it would cost about $3-4k.

I will monitor my exhaust for a sweet smell or any white smoke as @NetG suggested. I would also monitor my oil and coolant to see if I get any milky substance mixing between the two. If I don't see any of these in the next 1k mi, I should be good right?

I've also done some research and it seems that the normal operating temperature according to the coolant temp gauge is the 2nd line from the bottom as shown below:


Does anyone know what the actual temp is? I will be monitoring the real time temperature via an OBD2 reader so I just wanted to know what's normal. And what temp should I stop and shut the car off? If it reaches 215F?

Thanks guys!