Brandonlewis40

So i have a 1998 honda accord lx with 202,000 miles. Its leaking oil from the main rear seal and one other place near it on the transmission and it will burn through the oil when im on the highway causing the oil light to flicker and overheat right when i get off the highway. It will also over heat if im using the A/C for a long period of time. What could be the cause or causes of this issue?

Micro1989lxi

It could be multiple issues.

Engine oil is used for part of the cooling system, so if you are loosing enough oil that it doesn't show on the dipstick, this can certainly cause the car to overheat. Conventional oil will leak slower than synthetics through a seal, but only by a little bit. You could also try going to a 10W30 to slow down the leak until you get it fixed.

As far a overheating, be sure that the cooling fan is coming on. With the AC both cooling fans should be working. If you have been using tap or especially well water in the radiator,, it can cause blockages in the radiator cooling fins, adding to the overheating issue. Also a 2-+ year old radiator can be getting clogged. Take off the radiator cap with a cold engine and see if there is any mineral build up in the radiator.

Other causes would be a radiator cap that is not holding pressure as well as a pinhole in a heater hose or a hose that goes up to the intake manifold etc. Too much water or too much antifreeze ratio can cause overheating. Radiator fluid testers are cheap at any parts store and often in a Walmart.

While driving down the road, a car runs cooler s the air is moving across the radiator fins, keeping the car cooler. When you stop (pull off the highway) there is a lot less airflow, allowing for more heat. Also be sure that the radiator is not caked with mud or bugs or too many fins crushed as this also makes it harder to cool the water.

hondamark35

you mean onto the transmission from above and running down the side? the distributor base O-ring is a common leak point on this model. I don't remember what year the LX V6 was introduced, but I'll assume you have a 4 cylinder.

a leaking rear main seal is a small problem. you have just described a very serious problem. last time I noticed a rear main seal leaking on my car from the oil stain on the driveway, I put it off for 6 months and never lost enough to notice on the dipstick. I don't think the rear main leak is the real concern. it's leaking and/or burning off some other way to get the level so low the light comes on.

I agree with the cooling system advice. no leaks, good condition coolant, right mix ratio, free of flow restrictions, no trapped air pockets, fan(s) come on when they should, air moves across it freely.

Kind of half true. But what's the trade off? thicker or higher viscosity oil by definition is more resistant to flow which is why it leaks through seals more slowly, but that also means it will move more slowly through the very narrow spaces in the bearings and rings and cylinder walls where it is needed to lubricate and transfer heat. High-mileage oil in the proper weight (5w20 IIRC) would be a safer bet. the additives in it are meant to swell the old seals to slow leaks.

OP, when the A/C is on it's adding heat to the air that moves through the radiator as well as load on the engine to turn the compressor. Both of these systems you have suggested are already being overtaxed. don't run the A/C until you have this resolved. My suggestion is to top up the oil and coolant and drive the car to a shop to have it thoroughly inspected so you have the full picture of the leaks and anything else you'll need to make a good decision on what to do long term.

nicolaselias

At one point my volvo was literally pissing oil from the rear main seal, like.... a quart or more every 2 hours of highway driving, and even so I still had no oil pressure or overheating issues.

Sounds like you have a bad leak, but but once there is enough oil on the dipstick i wont stress that, and it shouldnt affect your oil pressure light unless you have some major other issue going on, or whether it is the oil pressure sender unit itself thats doing the leaking

Check through your cooling system, change the radiator cap regardless as cheap insurance, make sure the thermostat is good (lots of youtube videos on how to) and MAKE SURE you keep the oil and coolant topped up until you figure it out.

Using a higher viscosity oil or one of those high mileage oils will slow the leak just a tiny bit, for example a 10-40 high mileage oil, but that is just a band aid, wont fix the fundamental leak