Hey does anyone know if there is a leak in from the thermostat housing unit, does it cause the knock sensors to get wet and read it as a performance issue. thanks

 

holiday,

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Members here with the same model will be able to help.

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Graham

 

No, it would have to be a massive leak. In fact you'd probably have to submerge the car. What are the symptoms?

 

I disagree! The knock circuit is a high impedance input and even dampness can affect it. I suspect the OP has an AJ 27 engine, on which the knock detectors themselves crack and become very sensitive to moisture. Mine would RP on a damp day. All fixed by changing the sensors.

Many many times when folks have posted in the past about RP suddenly occurring, the answer was yes when asked if they had given the engine a bath.

BTW, holiday, it is wise to add your car's vitals to the signature since the various models can have very different characteristics!

 

Ross, I based my remarks on the relative positions of the two items, and the sealed nature of the sensors. I can see washing the engine, but I'd still be surprised if a thermostat leak would do it. Could be wrong though, it's happened before. Just ask my wife...........................

 

I can attest to the fact that an upper hose blown off the thermostat housing will definitely cause the knock sensors to go crazy. Dried out and ok after about a week.

 

My wife put you up to this, didn't she..............

 

heh, heh. The sensors on my AJ 26 engines have never given a problem, but each sensor in the AJ 27 (separately) started giving RP when any moisture, including rain, got near the engine. After removing them, I saw minor cracks in the plastic cases on each and the resistance measurement was much different than the specification from JTIS. I do not recall the connectors (which are actually on the thermostat riser), to look particularly vapor tight, so it seems like they could also be sensitive to even a little moisture which would track between connections.

BTW, I feel lucky that the bad KS were on the NA car!

 

I took my car to a mechanic to have the thermostat replaced and a week after my restricted performace light came on and i took it to another shop because the previous mechanic broke my manifold case and did not tell us. We noticed a few days later that there was a leak around the seal. We wanted to take it back to him but i was skeptical about his work ethics and plus he wanted to charge me for checking the code for the restr. perf. so i decided to take it somewhere else and was told it was the right knock sensor, but it comes on and off not every day though. that i why i asked if the fluid from the thermostat my be leaking on the sensors and causing them to malfunction. Any other suggestions please post. Other than that i will probaly have to replace the sensors.

 

You have the "upgraded" sensor that are susceptible to cracking. Look to archives as to the lower cost XKR replacements. AND... the NA sensors are pretty easy to change! Just remember to get a magnet in your socket wrench socket.

 

My XJ8 had a bad knock sensor, and while changing the tensioners on the weekend, I found the harness had been chewed through! I can only blame it on mice, I can't see any other way it got damaged.
A fairly easy fix, in the end.