Title. Not sure what I need to look for in terms of diagnosing problems. The only parts that I see damaged was the already broken coolant reservoir, which I've replaced. And a leak in one of the coolant hoses.

What happened. Drove around for a bit. Got up to 80mph which the coolant tank (patched by previous owner) didn't like. Coolant temp got up to 235. I was able to duct tape it all together, fill up, and get myself home with no other issues. A few days later, I had a 2.5 hour drive. I had not replaced the coolant tank yet and kept my speed below 70. Was totally fine until the last half an hour of the drive. During an overtake (I believe) saw temps get up to 240 and I was able to pull over and swap out the coolant reservoirs. Filled back up with coolant and kept going. Overheated again, this time up to 265 before I was able to stop and fix. And then again, it got up to 275 for 5 to 10 minutes (no more liquids and had to get to a store to get water/coolant). Stopped and fixed. A few days later, doing the drive back home, I was an idiot and did not plug in my obd2 scanner when I started. Driving for an hour with everything fine, then I noticed my coolant temp light come on. When I finally pulled over and checked the temp, it was at 282...

So, what do I do now? I've already gone through to find leaks in the coolant system and will be fixing those. What else should I check and be wary of? I do not notice any additional noises since this happened. All of the temp spikes happened due to coolant leakage due to the reservoir cap not being on fully, or hoses leaking. All of those issues will be fixed. I am still on the stock thermostat and will swap to an inline 180deg thermo today.

 

I would be on the lookout for head gasket damage at this point. General consensus is that overheating can loosen your liners as well, but you can normally hear that when the motor gets up to temp again.

 

That's what I'm worried the most about. I don't see any cracks or leaks, but I'm not sure what to look for or where to look. The head gasket was replaced before I purchased the car so I'm assuming the liners issues was dealt with at that time. Not sure if overheating can unseat them again. I don't have any service history and had no contact with the owner so I can't ask for more info.

Oh and I did check and have no coolant in the oil. I do not believe I have exhaust gasses leaking into the coolant but I'm going to figure out how to determine that for sure.

 

Heads, head gaskets, liners - nothing you will know for sure until you get the cooling system sorted. I would do an oil change and watch for A/F in the oil,you need to anyway after those temps as the exist oil will be compromised. Pull the plugs and check for moisture, and steam cleaning of the piston heads. But given your description I am betting the head gaskets/heads are done, and that is why you kept overheating. The coolant tanks holds 20 psi normally, so even duct tape and seals all would hold it. It sounds a lot like you were over pressured.

 

Very slim chance the previous owner put in top hat liners, that goes way beyond a simple head gasket job. A blown head gasket will usually show up as air in the system that can never be bled out, and may over pressurize your cooling system if it's bad enough. A leakdown test may be a good next step.

That kind of heat can cook your rings and cause oil consumption. If the head gasket is blown, which almost seems inevitable, you'll want to haul the heads down to a good machine shop to have them checked for cracks and straightness as well.

 

Yeah, that's pretty hot. The only thing that might have saved you is the cracked tank may have prevented any pressure buildup - at those temperatures you can often get pressures large enough to blow hoses off, so more than 30 psi. I am the lone voice on this, but I would not run that cap fully tight after that overheat event. If the gaskets are not fully blown now pressure in the cooling system is not going to help.

 

Sorry to toss some serious rain on your parade, but if the PO had the head gaskets replaced and it was done properly ( having the heads milled) your current heads may not be able to take another milling. There is only so much that can be taken off of the face. The head bolts will not seal the head to the block as they are made to fit the depth of the block and head together. I hope this is not your case.

 

@matt3502 at those tempe the heads could be warped,but yea the 260 plus temps are the problem.

 

Not having pressure in the system hurt him here since the coolant definitely boiled at those temps and caused further damage

 

So your losing coolant somewhere. Time for a pressure test I guess and hope your block is ok