Overheating question

[Nate88]

So I got my first slice of the downs in classic car ownership today.

Dad and I took the car around 80 miles from home, ran beautifully no problems. However, once we reached the parking lot (big event had to follow line of cars to parking) I saw the temperature rise and then it overheated with steam from the coolant bottle cap. Pulled over as soon as I could and shut if off. I had noticed the cooling fans not running right before it blew. We waited a bit for it to cool down And finally was able to get it parked.

So after enjoying the event for 4 hours or so while the car cooled down we went back and did some testing:
- The fans come on with AC so they are working.
- Felt the airflow behind the fans and they are both spinning.
- Jumped the outerstat wires and the fans came on.

So we decide to try and make it home leaving the AC on so the fans stayed on. However, after getting on the interstate the car overheated and steam again. I pulled over quickly and shut it off. We got towed home after that.

I do not have the blue fan fail module, it is the fused leads. I believe all the other relays (besides rpm) are original or look it.

Some questions:

1. How likely has damaged been caused to the engine? And if so what?
2. I believe the thermostsat may be stuck closed because even at highway speeds with fans (because of AC being on) the engine still overheated. Is this a correct assumption?
3. I'm pretty sure the outerstat is bad because the fans weren't running when it overheated and they do with it jumped out. What else could be the problem?
4. Would an auto parts store (Advanced Auto etc.) be able to get these two parts and would they be correct? Or should I get them from Houston?

Any help is much appreciated.

[kings1527]

So I got my first slice of the downs in classic car ownership today.

Dad and I took the car around 80 miles from home, ran beautifully no problems. However, once we reached the parking lot (big event had to follow line of cars to parking) I saw the temperature rise and then it overheated with steam from the coolant bottle cap. Pulled over as soon as I could and shut if off. I had noticed the cooling fans not running right before it blew. We waited a bit for it to cool down And finally was able to get it parked.

So after enjoying the event for 4 hours or so while the car cooled down we went back and did some testing:
- The fans come on with AC so they are working.
- Felt the airflow behind the fans and they are both spinning.
- Jumped the outerstat wires and the fans came on.

So we decide to try and make it home leaving the AC on so the fans stayed on. However, after getting on the interstate the car overheated and steam again. I pulled over quickly and shut it off. We got towed home after that.

I do not have the blue fan fail module, it is the fused leads. I believe all the other relays (besides rpm) are original or look it.

Some questions:

1. How likely has damaged been caused to the engine? And if so what?
2. I believe the thermostsat may be stuck closed because even at highway speeds with fans (because of AC being on) the engine still overheated. Is this a correct assumption?
3. I'm pretty sure the outerstat is bad because the fans weren't running when it overheated and they do with it jumped out. What else could be the problem?
4. Would an auto parts store (Advanced Auto etc.) be able to get these two parts and would they be correct? Or should I get them from Houston?

Any help is much appreciated.

1) Tough to tell. If you can pull your dipstick and the oil looks like oil and not milky, then you're probably fine and the head gaskets are probably intact. You can also look for the plastic screen at the oil fill and see if it's intact, as well. If it is, you're looking pretty good. The PRV is a pretty stout and durable engine that can take significant abuse but it is aluminum and has its limitations.

2) Good possibility given the fact that you had the fans on with the AC but still overheated. Might as well replace, especially if you don't know the service history of the car.

3) I'd definitely swap in a new otterstat. $20 part.

4) I'd just go ahead and order through your favorite vender. You can cross reference a lot of parts on the car but these are low $$$ items and getting them from a DMC vendor ensures that you're getting the correct parts, especially when dealing with the cooling system. The vendors ship things out pretty quickly.

Keep us posted on developments.

[kings1527]

Here's a great website on EVERYTHING someone would need to know about a thermostat and how to test to see which position it's stuck in.

https://axleaddict.com/auto-repair/c...roubleshooting

[DMCVegas]

Some questions:

1. How likely has damaged been caused to the engine? And if so what?

Depends upon the temperature as well as time length of time the engine was exposed to those higher temperatures. How high did the needle go?

Overheating doesn't always lead to instant head gasket failure, nor cylinder head warpage. However it can certainly cut the lifespan of the head gasket for sure. First thing to do would be to pull your oil filler cap and inspect the screen inside. How does it compare to this:

2. I believe the thermostsat may be stuck closed because even at highway speeds with fans (because of AC being on) the engine still overheated. Is this a correct assumption?

It is possible, but perhaps not quite guaranteed. Specifically because we don't know if you were low on coolant, had air in the lines, or if it was indeed a bad thermostat.

3. I'm pretty sure the outerstat is bad because the fans weren't running when it overheated and they do with it jumped out. What else could be the problem?

Nope. If you have an obstruction in the line due to any of the causes I just mentioned, there is no way that the hot water would ever have reached the Otterstat to trip the fans.

Then after you overheated, unless you burped the system up front too, you've got air bubbles that are not allowing proper coolant flow. That's also assuming you refilled with a 50/50 mixture of antifreeze to maintain the higher boiling temp, and didn't just add plain water back into the system.

4. Would an auto parts store (Advanced Auto etc.) be able to get these two parts and would they be correct? Or should I get them from Houston?

Stop right there. Do not just go out and buy new parts to throw at the car.

Probably best to go ahead and order OEM parts directly from a vendor. But in this case, you shouldn't even consider buying parts until you first diagnose if the ones you have are even bad.

In order to do that, you'll need to heat up some water in a saucepan on the stove, using a candy thermometer in order to keep tabs on the temperatures. DO NOT BOIL THE WATER! ONLY INCREASE TEMPERATURES TO THE NECESSARY LEVELS AS PER THE WORKSHOP MANUAL! Then expose the parts to the water to see if they function properly. Drop the thermostat in of course to see if it moves, and then partially submerge the Otterstat by it's electrical leads attached to alligator clips, connected to a multimeter to see if the thermal switch trips.

The first thing to do here is to perform a Pressure Test on the cooling system to ensure that you don't have any leaks. Then use the tester on your radiator cap. THEN you would move onto the testing of other parts. THEN you'd start buying new parts after you determined which ones were bad.

My two big concerns here personally are either a bad thermostat, or a leak somewhere such as a bad radiator cap which allowed coolant to escape and lower the fluid levels. But there are first ways to diagnose these parts.

Speaking of which, have you performed any recent work to any part of the cooling system?

Also, does anyone else here still shop at an actual auto parts store for car & truck parts? Between all the DeLorean vendors & Rock Auto, everything for my cars is purchased online at a significant savings.

[Nate88]

Thank you for all the replies. We will be doing these checks today.

Unfortunately the needle went all the way both times however I shut the engine off within 30 seconds if not faster. First time I didn't notice it until it was too late since I was watching traffic and pedestrians.

I will be buying any parts from a DeLorean vendor, just wasn't sure if they could have the same parts available at a local store.

I will update on what we find.

[Nate88]

image.jpgimage.jpg

Checked the oil and looks ok. No sign of milkyness.

Tested thermostat with heated water in a bowl. It opened, but the water had to be boiling before it opened. The only thing we can think of is if somehow when driving air got into the system and that's what made it boil over the first time. That or the thermostat didn't open when it was in the car.

We didn't test the pressure because the steam/coolant only leaked out the cap when it boiled over. No visual signs of leak at any other part of the system. Can the system leak without dripping coolant? Also no signs of coolant leak when sitting for several days.

Before we set off on the trip, we checked the coolant bottle without opening it and it was in the middle between max and min.

I do have the original coolant bottle and I think the cap is too. Since we have the cooling system opened should this be swapped out for the stainless version?

[David T]

You are on the right track. Replace the O switch and the thermostat. Bleed the system of all air. Check the dipstick for any sign of moisture, it will appear as a white froth. If you did pop the head gaskets it will continue to overheat and you can confirm by testing the coolant for combustion gasses.

[cdrusn]

I would begin by replacing the cheap parts first. The radiator cap would be number 1, if it isn't holding 15# then your boiling point goes way down. I've seen caps that wouldn't even hold 5# but seemed o.k. when you screwed them in. Thermostat is cheap, replace it with one that opens up early. Make sure water pump is working, check to be sure the engine coolant hoses are getting warm that will tell you the thermostat is opening. Check for water pump leak through the weep hole. As far as air in the system goes, it will eventually bleed itself out after relatively short warm ups and cool downs. The coolant reservoir is at the highest point of the coolant system so air will naturally try to get to the top of the tank and bleed itself. I would be running a compression check just to make sure the head gasket hasn't all ready been blown.

[Nate88]

Ordered a new O switch, thermostat, coolant bottle cap, and the gaskets and o-rings for the w-pipe. Hopefully this and a proper bleeding will fix the issue.

[Bitsyncmaster]

It's good your ran your AC to keep the fans running if the otterstat is bad but unless your AC was cycling a lot, that should have kept your engine cool. I would think your thermostat is bad or you had air trapped somewhere in the system. Did you happen to drive on any steep inclines around the time it overheat the first time?