Strange Burnt Plastic Smell?

[RG79K20]

Hey guys, new member here and this is my 1st post so hope I'm doing alright!
Anyway, I have a 1979 Chevy K20, 454, SM-465 4-speed. It was a nice day out last Saturday so I figured why not wash the truck...well I was being lazy and decided to take it to an automatic car wash (first time I've ever done that). As soon as I got home from the wash I noticed a very strong burning plastic smell when I was idling in my driveway. I've never smelled this before on my truck and best I can tell I've traced it to the front end, around the radiator.

I tried to rule out the obvious...no plastic bags stuck to headers or exhaust, no wires look like they got moved, no detectable leaks, all belts are tight, breaks aren't stuck, parking break not stuck, all fluids clean and full. I've been driving it around yesterday and today and the burning plastic smell is still around.

I'm at a loss...anyone have any suggestions? Thanks for helping me out!

 

[Georgeb]

Strange! Always scarry to smell and not somthing you want to ignore but do you suppose its just from the soap or wax stuff being sprayed directly at the front of the truck and getting on the radiator?

 

[austinado16]

Confirm that your ground connection at the blower motor on the passenger side firewall is still good, and tight. If that's okay, and the ground wire isn't getting hot, or the blower motor speed wires aren't getting hot (nearby bundle of wires at a connector), then you may have a blower fan switch in the dash that's failing. These can be taken apart and cleaned and sometimes repaired.

 

[RG79K20]

Thanks for the replies!

So here's a little update/new things I've noticed...

So after just over a week of driving it, the smell is still around unfortunately. I wish it was something as simple as soap on the radiator but that should have long burnt off.

The blower motor ground wire looks fine, and the blower fan is functioning as it should.

I have an aftermarket mechanical temp gauge as well as mechanical oil pressure gauge. At operating temp, the temp gauge stays at around 160F or slightly below and my oil pressure always hovers around 35psi at idle to just over 45psi when accelerating. While driving today, I noticed that at idle my oil pressure gauge was reading around 25psi and when accelerating it got up to about 40 (making me nervous)...also, when I shut the truck off, I noticed that the temp gauge started slowly creeping up and got up to about 190F when the engine wasn't running! AND...the smell is still there!

This is starting to look like something major might be going on and I really don't want to have to take it somewhere if I don't have to.

Again, any input would be greatly appreciated! Thanks in advance!

 

[foamypirate]

Thanks for the replies!

So here's a little update/new things I've noticed...

So after just over a week of driving it, the smell is still around unfortunately. I wish it was something as simple as soap on the radiator but that should have long burnt off.

The blower motor ground wire looks fine, and the blower fan is functioning as it should.

I have an aftermarket mechanical temp gauge as well as mechanical oil pressure gauge. At operating temp, the temp gauge stays at around 160F or slightly below and my oil pressure always hovers around 35psi at idle to just over 45psi when accelerating. While driving today, I noticed that at idle my oil pressure gauge was reading around 25psi and when accelerating it got up to about 40 (making me nervous)...also, when I shut the truck off, I noticed that the temp gauge started slowly creeping up and got up to about 190F when the engine wasn't running! AND...the smell is still there!

This is starting to look like something major might be going on and I really don't want to have to take it somewhere if I don't have to.

Again, any input would be greatly appreciated! Thanks in advance!

Temperature climb after shutoff is normal, as you still have a lot of heat in the engine and no coolant circulating to cool it down, so the coolant temp in the cylinder head climbs. 40psi oil pressure isn't anything to worry about either, in fact, it's a great thing.

 

[RG79K20]

Temperature climb after shutoff is normal, as you still have a lot of heat in the engine and no coolant circulating to cool it down, so the coolant temp in the cylinder head climbs. 40psi oil pressure isn't anything to worry about either, in fact, it's a great thing.

Well thats good to know about the pressure and temp! Thanks for the heads up...now just to figure out what is causing this dang smell, it's absolutely driving me insane lol.

 

[CSFJ]

probably a good idea to stop by the store and grab a small fire extinguisher rated for vehicles and rv's.

 

[Georgeb]

I would start looking for a hot wire inside a loom and yes get an extinguisher and make sure you have what you need to disconnect the battery in a hurry. Try to see it there are times it smells worse than others and develope a pattern.

 

[austinado16]

When I had the burned electrical/plastic smell, it wound up being the heater blower fan switch in the dash. I believe I posted a series of photos here, about how I repaired it. It was getting cooked by a bad ground connection at the blower fan, out on the firewall, and the load from the a/c clutch. I redid the ground in larger diameter, and put a relay on the firewall, that powers the a/c clutch. So the relay carries that load, rather than the wiring and blower fan switch's contact plate.

Your running temp seams low to me. You really want 180*F for proper oil lubrication. The TBI engines run even hotter than that, at 195*F.

My worn out (287,000mi) 350 makes 30psi hot, at speed, and only about 15psi hot at idle, running 10w/40 Synthetic, and one of the huge NAPA industrial engine oil filters........FWII.