Hi, Hoping to pick the brains of some of the wiser folk on the forum. My Mexico, like my last one, is reasonably fume-y after any decent length drive. Now- every classic car I have ever owned has been to some extent, but out of curiosity I took a portable CO monitor (already owned for a different purpose) with me for my long drive today. I clipped it to my seatbelt up near my shoulder to get approximate readings of what I breath, and was a bit alarmed with some of the findings... Windows up, 100 km/h the levels read around 30-40ppm; maybe falling to closer to 25-30ppm when I activated the fan (had fresh air lever open at all times with or without fan- although without the fan in my car the breeze coming through is only slight in the open position). Very occasional spikes with windows up to 60-70ppm. Windows down, 100 km/h saw things fall to 10ppm or so. Within 1-2 minutes of closing windows, back to 20-30ppm again. Of course, sitting still too long in traffic with windows open also saw things creep up to 20ppm, but then fall rapidly to 10ppm once moving. On the way back-I cracked open the rear vent windows and repeated the experiment; levels similar, perhaps 5ppm lower in all conditions with the rear vent open. Opening the front quarter vent always saw levels come up fast, at any setting. So- questions 1. Do I have a ventilation problem? 2. Do I have an exhaust problem? 3. Do I have a state-of-tune problem? 4. Do I not have a problem and these levels are fairly typical of a mid 1960's car with 4 Webers and 4.7L up front? 5. Which window setting (if any) would be expected to minimise CO levels>? Thanks for your inout... not sure if this is something I should be worried about.
Besides tracing down any potential exhaust leaks don't forget about crankcase fumes. If those are are just venting to the atmosphere like they do on my 1970 Espada, notoriously stinky cars, then you really have to check all firewall sealing.
Thanks- a general first question would be whether these levels are normal or not for a car from this period? A quick google found this document, which shows cabin numbers all over the place...
I don't think you have a state-of-tune problem: Best combustion maximizes the CO/CO2 levels.. so if anything, high levels are desirable.. ironically. - Art
Thought I should circle back with the outcome here. As you may know from my other thread, since writing this question my car has undergone a bare metal restoration; and after that was done we came back to the exhaust, and as suggested found cracks/ holes in the headers. They have been refinished, coated with all new gaskets- so finally, almost 12 months since my minor fender bender that triggered the restoration, I have the car back in my garage and sorted! Thanks as always for the good advice. Remi Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Hi Remi, did you repeat your ppm test with the restored headers/car? I would be very curious about the results, because my wife is also complaining about the exhaust fume smell in my Mexico. Ironically the fume smell is much more intense when the windows are down instead of up. It seems that the motor fumes that exit the little side vents in the fenders are sucked into the cabin when the windows are open. I had the best results (lowest smell) when all the door windows are closed, the vents are open (no fan needed) and the rear vent windows are in the open position. I am pretty sure that i have no leaking gaskets/firewall holes whatsoever in my car, because it is fully restored. Of course every vintage car smells of petrol fumes more or less, i am used to that. But the levels are totally different between cars, for example i had much more trouble with that in an E-Type than in the Mexico or an MGB GT for example....
In my E-Type, I have always had fumes in the cockpit and need keeping windows open. I think that in my case it is due to exhaust fumes coming in through the boot (there are various small holes in its bottom for different purposes, not all of them being correctly plugged), because of the teardrop back shape of the E-Type that promotes air turbulences and suction inside.
Not yet- only picked it up Thursday afternoon, so haven't had a chance to go for a proper drive yet- but will take my meter and report back.
An update as promised. Had the opportunity to take the car for a long drive yesterday (200km), and took the CO meter with me. Windows down in slow traffic the levels were much better- around 10ppm, with occasional higher spikes if the breeze was blowing from the engine back into the car from outside. Windows up on the freeway- fresh air lever open, 0ppm... 0!!! With or without fan, with or without A/C the level stayed at 0. If I closed the fresh air intake and recirculated inside air, there was a very slow creep up to 15-20ppm over half an hour or so. Interestingly, when I pulled off the freeway into stop start traffic the level shot up super high (150-200ppm) very quickly if the fan was on with the fresh air intake open- so when the car is standing, a fair amount of engine fumes are obviously entering via the fresh air intake. So- lots of good lessons for the future- highway driving can be done with windows down, or up with some fresh air coming in without dramas. But in stop start traffic (which I try to avoid anyway), it is better to switch the fresh air intake off +/- have the windows down. Overall- very happy to see a positive result after all that money spent on the exhaust. Of course I still smelt like an interesting combination of petrochemicals and leather, but that is part of the fun. And for any of you who feel unusually tired/ have headaches after long days in your classic Maserati, maybe a good idea or two. Remi
Very good Remi, that confirms my findings more or less. A real good thing are the rear vent windows. But i am curious about your findings with windows down in slow traffic, because then i experienced more fume smells than with windows up - probably my side vents in the fenders are different. And the electric fan is more or less counterproductive. But alltogether a good result which confirms the value of a good restoration and a tight exhaust
One of the worst Maserati's for sucking engine compartment fumes in at high speed is the Bora. I was in a friends once and unbeknownst to us a massive oil leak developed spraying onto the headers. At 140 mph when the windows were opened the car filled with blue smoke very quickly. It came right thought that center tunnel which isn't sealed very well. I never noticed any fumes in mine so it must be down to the extreme operating circumstances. I also never had any exhaust leaks.
