DanADaMan

So, had a local C4 owner stop by today to help me diagnose my overheat problem on my new-to-me 90 vert. As I stated in my previous post, the previous owner put in new thermo, new fans, and even a $3700 head gasket replacement. He told me he thought the rad was needing replacement.

Turned out to be a bad rad cap, and the analog temp sender is faulty. We basically put on his cap and the smell of antifreeze was gone (which I used to be able to smell about about 10 min of running the engine. We also used the a/c controller inside the cab to read the digital temp - it was always perfect (as it should be) and the fans turned on when needed which would turn the temp back down. But the analog gauge was reading higher temps than the digital read-out. So my question, where is the analog temp sender on a 90? Is it hard to get to and replace.

So after realizing I had no real overheat issues after replacing the cap, we drove it on the freeway at 150 km/h and it ran real nice. But when getting back we saw a little smoke coming from the engine compartment. Looking underneth, there was lots of oil on the frame. The smoke was coming from oil hitting the hot exhaust pipes and smoking off. I'm gonna clean the oil tomorrow, but any ideas (or common issues) why I would have oil leaking? BTW - there is nothing obvious from the top in the engine compartment, so it is somewhere underneth. There was also oil on the entire cross member/framing which went all the way to the rear of the car. Any ideas why I'd have engine oil all the way back there - could it have been from the drive on the freeway at high speed. BTW - the oil was full and looked good, and no major drips leaking onto the driveway.

Any advice would be appreciated.

Thanks

jv9999

Common would be leaking valve cover or rear of the intake gasket. Oil then runs down to the exhaust.

eutu1984

confirm that it is engine oil and not trans or power stearing, my 90 used to leak from the front engine seal on the timing chain cover.

WVZR-1

OP - I'm guessing your local "acquaintance" is Vikingtrad3r", Ryan or Rian? I ain't sure - I guessed Ryan.

Analog sender should be in the rear of the RH Cyl Hd but there are a couple different possibilities for connector. Identify your connector type from this post and use that information for an AP store in the vicinity.

https://www.corvetteforum.com/forums...post1592982399

Your acquaintance has the FSM so you might want to check the gauge accuracy first before buying/replacing sender. Maybe it's actually the gauge and the sender would be wasted $$$'s and effort.

The oil leak if as critical as you seem to mention might possibly be the fault of the $3700 repair. Check maybe the Oil Pressure Sender components and maybe the rear of the intake to block. The OPS components are right there also. A 90MPH/150KPH extended drive could certainly push some fluids.

antfarmer2

Find and fix the leak ignore the analog it will never be right.

VikingTrad3r

yup!

Dan, you asked me yesterday about where the leak is coming from, i disnt really give you a straight answer because the reality, with your low mileage car, similar to my low mileage 85, is that it can/and probably is/ leaking from multiple areas.

i had literally EVERY seal leaking from my 85.
- rear china wall and in your case we saw oil coming up the rear passenger intake manifold bolt, 2nd from the back)
- both vc's
-head gaskets (sispect as they were just done, and, i saw they used black rtv on the intake gaskets, which should have gone on dry (opinions vary here but insteuctions are to install dry) which tells me they likely messed other things up to.
- timing cover
- oil pan
- ops
-rear main
- oil cooler

the oil leak can be at the very front, and be blown back.

hence the advice to use hot water with purple cleaner to clean the underside of the vehicle because you will never know where it is coming from until you clean it all first. note that with purple cleaner (from auto value) do not apply to your top engine aluminum it will make it blotchy. let it soak on the oil for a minute and then hot water spray it off. the hot water isnt required if you hit it with purple cleaner.


your transmission is also on the table, even though there is for sure an oil leak your trans fluid is very clean and its probably leaking and blending with the oil from the pan or tailshft or tailshaft oring or vss or the servo cover. in my case, every single place was leaking.

then there is the oil seal at the rear diff. thats probably leaking too.

this happens with low mileage cars it is what it is.

if i was you, i would drive the car onto the grass there, place 4 pieces of 3/5 plywood bigger than the base of the jack stands, jack it up, then go to town on all that oil. it will stain your driveway.

you will need to remove the X brace and also once tou have cleaned everything you will want to remove the bellhousing inspection plate to see if the flywheel has oil on it and use a powerful led flashlight to see if there is oil comi g from the rear main seal.

there is 5 hours of work just in the cleaning, unless you can jack it way up on a lift and pressure wash it.

this is all speaking from experience on my 85, which was in as nice of consition inside and out as yours, low mileage, but she leaked bbaaaadd.



to sum up, there are about 20 places it could be leaking from and likely more than one place. your bill will be in the thousands if you pay shop rates to clean and repair your oil leak. you could buy that lift for what it will cost to get the oil cleaned and repaired because chances are it will be the first time that the mechanic will be doing the job. unless ylu take it to weatern corvette off macleod over the winter. they would do it quick and correctly, but i believe shop rates are 150$/hr and parts are 3-4 x what they cost on rock auto.

most people buy an old car and doesnt matter that it is leaking/smoking/sputtering. the thing is we buy a vette and we want to get it running like new because they are timeless and they will never end up in the junkyard. people think owning a vette is expensive...its not...its our desire to fix them and getting running top notch.

long post! you have an incredibly nice vert! and it pulls very strong.

personally, id get that new cap, clean it myself, and then see where the oil leak is.

i would not rush into the oilleak repair until you see yourself where the leak is from.

notwithstanding that your oil dipstick through me a curveball. lol.

VikingTrad3r

its probably not that bad. i think im just jaded because mine was. maybe it will just be the oil cooler and thats a 7$ fix.