Clogged Cat And Operating Temperature

Yes, it is true... old cat will cause engine temp to rise. Same is said for plugged radiator too.

A clogged CAT would show itself by choking off the motor at high speeds when high volume of exhaust needs to be processed. The exhaust volume at idle is quite small compared to highway speed.

Gas engines' temperature does rise pretty quickly at idle so that's not unusual.

How do you KNOW the radiator is clean - inside and out? Has a shop flow tested it? Does the auxiliary fan come on at its specified temperature?

It could be that the idle air / fuel ratio is a bit rich; that's a theory on my part not a known (to me) cause of high engine temperatures.

Thanks you for responding, Tiger and T.G..

However, the 10-15 degree temp increase I've been experiencing at idle is unusual for my car when it is still fairly cool out in the Northeast, and the AC has been off .

I installed a new radiator last fall, because I thought that the increased operating temperature I started expriencing then was probably caused at least partially by the original radiator, which had also started leaking at the transmission cooler connection. Of course, when the ambient temperatures went down during the winter, the car ran cool, even at idle.

I'm wondering now, however, if it's possilble that the radiator I installed, which came from China, doesn't have the cooling capacity of the original, perhaps because it's core doesn't have as many rows of fins.

Yes, the fan comes on as expected when the operating temp exceeds app.

Hmmm, I never thought of that, but I should have mentioned that my cat is definitely clogged car, because my car needs valve stem seals and has been burning oil. So, could that be responsible for the increase in operating temp?

Thanks again for the help.

Bill

A "clogged" CAT will stop the motor; yours isn't clogged - perhaps ineffective (depends on the state emissions test) bu not clogged.

OK, the new radiator may well be the reason for the temperature rise.

Burning a bit of oil, IMHO, would not noticeably raise the operating temperature.

Dilute coolant has a lower specific heat capacity than 50/50 mixture; another possibility.

Given these possibilities I'd count the replacement radiator's tubes vs. OEM and question the heat dissipating core material vs. the OEM.

Partially clogged cats is the problem for elevated running temperature. Oil will clog the cat sooner or later, so Bill is correct in his accessment.

I don't care for new radiator efficiency... it makes no difference. I did that on my 380SE before I sold it... new radiator, new thermostats, etc... still ran hotter than normal. It definitely is the cat.