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MG Midget and Sprite Technical - Bleeding Paint

With my Sprite's engine and gearbox both overhauled and ready to go back in, I decided to tidy up the engine bay and give it a quick spray. For most bodywork I have usually taken it back to bare metal, but not every time and, so far, I have never had a problem with my new paint reacting with the existing paints.

I considered just spraying top coat but decided to play safe and give it a coat of primer as a sealer. I sanded all the surfaces and wiped them thoroughly with both Lechler Silicone Remover and thinners before spraying.

90% of what I sprayed yesterday is absolutely fine but there were annoying reactions in a couple of places, notably the inner wing in the first photo. I gave the affected areas a thorough sanding back, removing all of yesterday's primer and a lot of the old top coat, in places revealing the original Tartan red.

I also wiped over with thinners again, which resulted in one of my typical self-inflicted problems with the cross-member, which had been fine until I put my pot of thinners on it and removing a ring of paint.

The whole area received a more thorough wiping with Silicone Remover before spraying with Lechler Monporimer again: .

Before I had finished, the inner wing was bleeding again and spraying over it again just aggravated the problem.

I thought the Monoprimer would act as a sealer but clearly didn't. Can anyone suggest a sealer that I can use before top-coating - or could I get away with going straight to top coat - after I've removed all those runs.

This is another of those 'quick' jobs that's threatening to turn into a three-week epic.

Colin





C Mee

I'm about as far away from a paint expert as you can get but also have had issues with using thinners to clean existing paint before spraying. I found panel wipe cured the problem.
Thinners and panel are similar but ASUI not quite the same formulation.
Jeremy MkIII

Colin
I agree with Jeremy. Using thinners to clean up/ prepare the existing surface may have softened up the old paint and caused your problem. I'd only use panel wipe - that's what it's for AIUI.
Bill B

Thanks Jeremy and Bill.

Before spraying the first coat I used a quick wipe with thinners hoping it would help the adhesion. It was followed by a more thorough going over with Silicone Remover. I did that to the whole area, it was just this localised area and a few other spots where this happened. 90% of what I primed is fine.

I rubbed this area back far more for the second spraying and went over it with panel wipe a couple of times,no wiping with thinners. Giving it another quick squirt when the bleed appeared just made things worse.

I've been to the paint supplier today, expecting to come back with a can of sealer/isolator. His advice was to sand back to bare metal and then spray with epoxy primer. I'll see how that goes.

If it was on the right side I would have assumed oil contamination but this is on the left side, away from anything oily.

C
C Mee

Whilst I'd agree with previous posts about avoiding thinners for cleaning panels unless its fully cured 2k paint or powder, I'd stick to panel wipe. The pattern of poor coverage looks to be caused by contamination so would agree with the paint supplier to sand back, a pain but unfortunately looks to be required.
Tim Lynam

I don't know what has caused this it but at one stage with painting my Frogeye I got similar colour weeping and a sort of fine river - like fissuring of the paint surface. River like in that it looked like a satellite image of an extensive river delta.
But maybe interesting that it was in a similar area of the inner wing - it's where one might expect back - blast fuel contamination from the carbs to concentrate in the paintwork over a period of time. Might this be significant I wonder?
GuyW

To me it looks a bit like the panel and possibly the air temp were too cold- - I'd be rubbing/blocking it back and get a heater in there to get things nice and warm then dust a real light coat on and let it dry then another dust coat and let dry---plenty of drying time between light coats, keep going untill you've got it nicely covered----Same with the colour coat, just lightly dust the first couple of coats on and be patient, give it plenty of time to dry out between coats, specially the first couple---and with the light coats, hold back on the thinners as much as possible.
willy
William Revit

Guy. I think fuel blast is unlikely as this area is forward of the carburettors.The fuel line runs across the area but through new hose and I haven't seen any sign of leakage.

Willy. Temperature might be the problem as the air temp was below 10C and high humidity. However, there had been a low wattage pipe heater underneath the area for several hours and a fan heater blowing into the engine bay for a couple of hours so that most of the affected area was warm to the touch when I was spraying. The fan was not running while I was spraying. This area was at the warmer end of things, there have been no issues further back into the gearbox area or on the opposite side.

C Mee

Hmm - bit weird, as your paint man advised 2 pak primer will fix it but i'd still just dust the first coat on and wait till it dries out before giving it more, bit weird all the same

willy
William Revit

I did the whole of my car (the other one) in 2 pack epoxy primer in stages, mainly as a rust preventative and water vapour proof barrier during restoration as it was to be a long period before final top coating. Much of it was roller applied. It made a good base for further work but is very hard to flat off adequately so was later over sprayed with a conventional high build primer to get a better prep surface for colour coat spraying.
Long winded way of saying 2k epoxy is good, but hard work!
GuyW

Hi Colin, sorry to hear of your painting woes. As you say, the quick jobs are the ones that can take a while!

What’s your plans for competing with the car this year? Are events at Loton Park going ahead?

Cheers
Mike
M Wood

I think I might have solved the problem.

This is 2 hours after a coat of Epoxy primer,no reaction showing. The previous reactions appeared immediately. I only sprayed the affected areas, now I just need to decide whether to spray the top coat or go over the whole area in Epoxy first.

Hi Mike. After a period of turmoil that lots of clubs go through from time to time, the light at the end of the tunnel is much brighter now. Whether the season begins as intended in April depends on the track works being completed and the MSUK track licence issued. I'm looking forward to finding out whether I have solved my gearbox issues and whether a fast road cam will allow be to break the 70 second barrier.

Colin


C Mee

Glad it seems you've cracked it Colin👍
Jeremy MkIII

Job Done!

It's not concours - but then, neither is any other bit of the car. At least I think it looks better than it did before.

I am definitely a two-pack convert and will be using it to prime that left-hand wing that suffered paint when my gazebo collapsed on it in a gale at Harewood in September.

Thanks for your comments and suggestions.

Colin

C Mee

Colin

Glad to hear you have cracked your paint issues. Thanks for the update on your hillclimb plans and what is happening at Loton Park Hillclimb.

Cheers
Mike
M Wood

This thread was discussed between 05/02/2026 and 12/02/2026

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