Vapor Lock?

Got a 1998 Caddy Deville with 133K on it. I have had this term thrown my way a couple of times when I have described what has happened to me numerous times between August & October. Traveling highway for about 25 miles letting the car sit for a full work day(about 9hrs) then the car overheat on me in less than 3 miles when I try to make the same 25 mile ride home.

Would it really be worth the investment to have the car go into a shop and have the engine work done being it would more than likely cost more that the car is worth to fix, or should I try trading the car in at a Carmax type dealership and move on.


Not sure today’s cars can vapor lock. However, overheating means you have a cooling system issue. Have you replaced thermostat? My first inclination would be that it is sticking intermittently.

That was the first thing that I had done…Overheated the very next monring.

Can we assume you have fresh coolant put in at the time of the thermostat change? If the coolant concentration is not sufficient for the temperatures you are experiencing, then icing of the cooling system might be occurring.

Have you changed the radiator cap and did/does this car have dexcool in it? If you had dexcool, there are some conditions that can cause it to gel up, though I believe that when this happens, it is full time, not intermittent.

If this could be the cause, then you may need a power flush of your cooling system, then a complete drain and refill with a “universal long life” coolant/water mixture. I normally do not recommend any kind of flushing of a cooling systems and certainly not a chemical flush, but in your case a power flush with a machine may well be justified. Just don’t use any flush chemicals. At least replace the radiator cap if you have not done so.

If the fans are turning on when it over heats and you are sure that the new thermostat is working ok then it may be time to replace the radiator as it may be clogged up. Also have the shop check the coolant for any exhaust gases in it. There may be a head gasket leak causing the coolant to get extra hot.

Yes fresh coolant was replaced when the new thermostat was put in. Icing? Do you mean letting the car sit for the time I am at work or overnight?

As far as I know dexcool has not been used in the car. Especially since I have had it(dec. 2009)

I will have to check on the radiator cap idea. Dont know that it was a point looked at the car went to the shop any of the 3 times it went to the shop for the overheating.

I am not very savy when it comes to recognizing who or what type of mechanic or auto shop to have a “flush” done. Would a place that specializes in radiator/coolant systems suffice for what you have recomended, and would they possibly be able to diagnos without the engine coming apart?

I wonder if there is a air block somewhere in the system?

Vapor lock is not applicable here. That’s a term used on carburated to describe a specific fuel delivery system problem.

It sounds like you have a cooing system problem perhaps exascerbated by the engine compartment being heated up after shutting the engine down (a normal condition) and never really cooling down full while sitting in the sun. In short, a basic cooling system malfunction.

You’ll need to go through all the basics on this one; checking the radiator for flow, and for its ability to dissipate heat effectively and evenly (clogged tubes). This can all be done by any radiator shop.

The radiator cap can be easily tested…a better idea than simply replacing it in this case in order to know if it’s the cause of the problems.

The T-stat can also be easily tested.

Sometimes older hoses will seperate the inner liners from the outsides and the liners will collapse and restrict the flow of coolant. New hoses are cheap.

The pump can also be tested. The impellars can erode away and the pump no longer pump efficiently.

Lastly but not leastly, it’s a simple thing to do some preliminary tests for a headgasket leak. The coolant can be checked for the presence of hydrocarbons, and if bubbles are coming up through the radiator fill hole (cap off) while the engine is running that’s a pretty good indication that you may heva a blown headgasket. The combustion gasses blow through the hole and migrate up and out as bubbles.

With the exception of the headgasket, all of these tests and repairs of needed are affordable.