I wasn't sure whether to post this in general technical or in the Disco II forum, so I am doing both. Thanks!!

Hey everyone. This is our first post, but my girlfriend and I have been active readers of the site for some time. We have found it especially helpful in the few repairs we have done so far.

Anyway, we have a fairly straightforward, if bizarre, question for you experts. My question: Can a cooling system that was leaky but did not have any overheating problems suddenly start overheating when the leak is plugged?

I am providing some background info below.

We have a 2001 Disco II with 134k miles. It has been having some of the typical cooling issues as of late (needs a quart of coolant every couple of weeks, gurgling noise, etc). Anyway, my girlfriend brought it in to a mom and pop shop here in Atlanta a few weeks back to get the heating issues fixed. The shop replaced a lot of components in the cooling system, including the head gasket. They did not replace the radiator because this was replaced by the same shop a year ago. I was not involved at this step.

The shop called us this week and claim that the system no longer has any leaks, but the year old radiator must be replaced because it is clogged and causing the system to overheat. They say they found some stop-leak residue in it and that must be causing the leak. I have no idea where the stop leak came from as the radiator is only a year old and the only person to open the hood over the past year just changed the oil. But, the stop leak is beside the point. I am confused as to how the system is suddenly rapidly overheating when it didnt before.

My question: Can a cooling system that was leaky but did not have any overheating problems suddenly start overheating when the leak is plugged? I have a sneaking suspicion that the mechanic is making up the stop leak situation, and the new overheating problem was caused by something they messed up when making the most recent head gasket repair (or there is a stop-leak clog, but it was caused by the mechanic when he or she was trying to fix this issue last week). I cant possibly figure out how a system that didnt have any overheating problems before (it just required coolant to be added periodically) suddenly starts overheating once its leaks had been plugged. A newly pressurized system wouldn't cause this right? Am I missing something?

 

actually yes, We saw the same problem on a disco two same year. the stop leak let go into the radiator and caused intermittent issue with overheating. just flush the thing out and it should be fine.

 

Thanks Rovin, that was my next plan of attack. But wouldn't the car have had overheating issues before when the system was leaky and had the clogged radiator? Why would it start having overheating issues now all of the sudden? That is what makes no sense to me. I have no doubt that stop-leak can cause overheating. My questions is why didnt it occur before the system was leaky AND clogged.

 

The person who replaced the radiator may not have actually replaced it... Or they were the ones who put the stop leak in it... OR you could be right, the current mechanic might have tried to solve the problem with stop leak instead of repairing the head gaskets. You could just ask the guy if he tried it and how he knows the radiator is clogged. If he did use the stuff, then have him do a flush like Rovin4life suggested. In the end, you are speculating and do not know for sure who is not telling the truth. However, if the radiator is clogged, you need to fix it... Regardless of who's fault it is, or you will do reversible damage to the engine.

As for it suddenly overheating, it could be a number of things that I dare not say until evidence suggests so. In other words I don't want to scare you . The thing that gets me, is you were adding a quart of coolant every week. That is pretty high coolant consumption in my opinion... How long were you doing this? Do you still need to top up the coolant? and, how quickly does the engine overheat?