Exhaust fumes in cabin even when driving open

[dantvrgriff]

Hi

I have my Griff 500 for 8 years and always had the feeling that I could smell exhaust fumes when driving the car – be it open, in targa or closed. Often when out driving my cloth would smell badly of exhaust. Things did not improve since running a full decatted Y-piece. I have a new trunk seal and have sealed the Y-piece connections as good as I could – also have closed the rear vents to the trunk.

Is it a design flaw caused by turbulence via the rear of the rear or can I get this under control. Any suggestion is most welcome

Cheers

Dan

[Bristol ave fag]

You may have a small crack in the exhaust somewhere check handbrake gaiter and gear lever gaiter have no holes in them and are not letting air in from underneath also under the front of the body foreward of the chassis there should be a splitter fitted and should be the lowest part of the car. check that it is still there.

[lancelin]

Hello, I had exactly the same problem. Fumes circulate around the boot when driving and get into the boot via a poor boot seal. The number plate, rear lights can also cause a leak. When fumes are in the boot they then pass over the boot wheel arches and enter the cab via the access cutouts for the door locks. A thin badly connected carpet is the only thing covering the door lock cutouts. There are also small vents at the bottom of the rear window. Block all these holes and the problem is solved. A good fitting boot seal might also help! Not easy on a TVR! It never fits perfectly. I used a cheap eBay hand held carbon monoxide detector to prove I fixed the problem. I used foam to block the rear window vent holes and plywood plates to cover the door lock holes. Silicone sealant around the edge of the plywood create a perfect seal. Servicing the door locks is now slightly harder but not a big deal.

[Bristol ave fag]

How its meant to work when when driving is air enters cabin that cant be helped withe the roof off air leaves cabin through rear vents to the boot then leaves the boot through the holes in the floor behind the tank.The front splitter must be in place with the leading lower edge facing foreward this causes low pressure underneath the body and this pulls hot air from under the bonnet down to lower under bonnet temp and also at the rear pulls air out of the boot.

[lancelin]

Need to think about this but I now have zero carbon monoxide entering the cab with the roof on or off. Pre mods I used to get a consistent alarm and reading on my meter. We need a wind tunnel experiment with smoke to see where it’s all going.

[Boosted LS1]

British gas will sort it. They have a call out number but their van won't be quick enough. Defo block up body seals and check for exhaust leaks. Is the bonnet sealed?

[Bristol ave fag]

Tests were done to address buffeting the bonnets would lift and the under bonnet temps were very high, turbulence underneath was the cause some of the early cars had to have the splitter retrofitted and ive seen them fitted the wrong way round, the holes in the boot floor have always been there for ventilation.

[dantvrgriff]

Thank you for your feedback.

I checked under the car and I do not have a splitter - if I understand correctly I should place one just in front of the end of the frame. I will try to find some stiff rubber or plastic (maybe cut from square drain pipe) and make one. Not sure how long it will stay on though.

Also noticed that I have an opening at the gear lever gaiter.

Will see if this helps and also look into the door lock cutouts.

Cheers

[Bristol ave fag]

dantvrgriff said:

Thank you for your feedback.

I checked under the car and I do not have a splitter - if I understand correctly I should place one just in front of the end of the frame. I will try to find some stiff rubber or plastic (maybe cut from square drain pipe) and make one. Not sure how long it will stay on though.

Also noticed that I have an opening at the gear lever gaiter.

Will see if this helps and also look into the door lock cutouts.

Cheers

Powers has them at a reasonable price, you can fashion one,should be alloy tho, place it about 2 inches in front of the frame you can put a bead of sikaflex on to bond it then just use pan head screws. I would make sure the holes in the boot floor are still there and the cabin can breathe to the boot/vents open.

Edited by Bristol ave fag on Tuesday 12th May 15:53

[Boosted LS1]

The gear lever gaitor would be very suspect. I imagine a lot of fums travel down the tunnel.

[dantvrgriff]

I read that some people suggest putting scoops at the trunk venting holes under the car in order to pressurize the whole trunk and thereby avoid fumes crawling in via the back. Any experience with such ?

[The AJP Griff]

Boot seal is by far the most common cause. I had this on mine and although I thought it sealed well it hadn't. I think that possibly air pressure lifts it a little so what you think is a good seal when static is not a seal when your running. Also make sure the side windows and targa seals seal tightly to the glass all around and past the quarterlight as any gaps along there will effectively suck the fumes in as your going along. I've had 3 griffs and a chim and until my present griff I never had the problem. This griff I thought it was incurable! None of my other cars needed blanking off bits or scoops as they didn't have the problem and now my current one doesn't either :-)

[andy43]

Seem to remember the early precats had this problem fixed with tailpipe extensions. Boot seal would be my first check as above though.

[dantvrgriff]

When checking the car over the weekend, I noticed that the carpet in the trunk lid is completely full of black sod. I took the car for a drive and put a fresh towel in the trunk – it smelled badly afterwards. I do have a quite new trunk seal in place but it clearly does not do the job – I think I need a higher seal. Any recommendations ?

Cheers

[lancelin]

I have the higher seal from racetech direct but I needed to add small spacers to the hinges to get a good fit. I’ll try the old towel trick to see if it’s sealed but to be honest I don’t mind having fumes on the boot, I only have a toolbox in there. I made sure the fumes don’t get back to the cab by sealing the door lock holes!

[Griffo400]

I had this problem when I bought my Griff, I put some Plasticine along the seal to see where the gaps were. This was along the closing/lock edge. I found that there is a channel in the lid along this edge so I placed strip of neoprene sponge rubber into this channel which closed the gap.
I also filled the gaps over the wheel arches to stop any fumes getting through to the cabin.
Regarding the vents in the boot floor, my May 92 doesn’t have them. Not sure when tvr started putting them in.

[Bristol ave fag]

Griffo400 said:

I had this problem when I bought my Griff, I put some Plasticine along the seal to see where the gaps were. This was along the closing/lock edge. I found that there is a channel in the lid along this edge so I placed strip of neoprene sponge rubber into this channel which closed the gap.
I also filled the gaps over the wheel arches to stop any fumes getting through to the cabin.
Regarding the vents in the boot floor, my May 92 doesn’t have them. Not sure when tvr started putting them in.

The holes in the boot floor should be there, the boot compartment should be ventilated externally as for blocking the cabin off, if your tank started to leak you might not smell it. and if there are no holes in the floor you might end up with a lake of fuel in your boot. Don't mean to alarm but its how it was designed.

[Bristol ave fag]

You see how this might differ for others say s or wedge as the tank is external.

[lancelin]

People, please get a Handheld carbon monoxide detector from eBay! They are cheap and give a digital reading. Driving a car with fumes entering the cabin is very dangerous for obvious reasons and who knows what the long term effect is!!!! Use the meter to try and find out where it’s coming from when the car is stationary and when it’s moving. Make changes then measure the levels. So many different possibilities but isolating the boot air from the cab fixed mine. There was a direct path for fumes from the boot to the door lock holes. The edge of the carpet loosely covering the holes was black!!

[Griffo400]

Bristol ave fag said:

Griffo400 said:

I had this problem when I bought my Griff, I put some Plasticine along the seal to see where the gaps were. This was along the closing/lock edge. I found that there is a channel in the lid along this edge so I placed strip of neoprene sponge rubber into this channel which closed the gap.
I also filled the gaps over the wheel arches to stop any fumes getting through to the cabin.
Regarding the vents in the boot floor, my May 92 doesn’t have them. Not sure when tvr started putting them in.

The holes in the boot floor should be there, the boot compartment should be ventilated externally as for blocking the cabin off, if your tank started to leak you might not smell it. and if there are no holes in the floor you might end up with a lake of fuel in your boot. Don't mean to alarm but its how it was designed.

I take your point BAF. I’ve seen a small 3/8” 10mm hole on either side of the boot floor by the wheel arch which would be drain holes in the event of a fluid spill. These are the only holes I can find. There are certainly no obvious “vents” to be seen.
On another point, when I removed the tank there was an overflow pipe coming from the filler neck which flowed through a valve of some sort behind the tank, then out through the bottom of the boot and is tie wrapped to the lower wishbone. My question is, how does this valve work, what does it do?